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f1rocket
01-20-2005, 08:09 AM
Okay, this is the debate section, right? So let's entertain a discussion regarding alternative engine options.

I did a little research. I looked at all the RV accident reports for 2004 and pulled all the "engine problem" ones. I found 7 accidents. 5 of the seven involved Lycoming engines, 1 involved a Subaru, and 1 involved a Chevy V8.

Within those categories, I looked at final reports to see the root cause of the engine problem. On the Lycoming, 1 is a preliminary report so I don't know. 3 were caused by fuel exhaustion, 1 by a oil cooler line failure. None were caused by any internal engine problem. The Subaru went down due to vapor lock at cruise. The Chevy went down because of internal engine failure of the main bearings.

What can one derive from this? Not much really, but you can extrapolate some indications. When you consider the tens of thousands of hours put on Lycomings each year, it sure looks like the Lycomings are pretty reliable as long as you feed it fuel and oil. When you consider the very small number of hours put on alternative engines in a year, the picture is less rosy.

I guess that's my point. If you chose to drop an alternative engine in your RV, be sure you're willing to accept the proposition that you are a powerplant test pilot. Just because there's a few Subarus, Mazdas, and Chevys flying successfully, doesn't necessarily mean that your usage will be trouble free. There aren't enough hours put on these engine to derive any meaningful statistical conclusion as to their reliability. I'm not saying that they aren't reliable, and I'm not saying that they are. The point is there's no numbers to prove it one way or the other. If you can live with that, then go ahead and experiment.

One of the reasons folks choose the Subaru package, in particular, is cost. I suspect, but would like to see some hard numbers, that when its all said and done, you will likely have nearly as much money in a Subaru package as you will in a Lycoming. And don't quote me prices on the NEW Lycoming, because you're not getting a NEW Subaru either. You're getting one out of a salvaged automobile. When you consider resale value of your RV, I bet that Subaru will cost you much more money in the long run.

I'm a chicken, I admit it. When it comes to swinging the prop around, I don't mess around much. People have been trying to convert auto engines for aviation use since the 1960s. Personally, I don't think there's any magic out there to be uncovered. I have confidence in my building skills so I'm not afraid of pulling the wings off or losing my tail feathers. But when the prop stops turning, I have a big problem and a heavy glider on my hands.

I think there's more promise with newer designs like the diesel and turbine engine prototypes. In the meantime, I think I'll stick with what has a proven track record of reliability. I admire all you test pilots, and I hope your projects are very successful and safe.

fredmoss
01-20-2005, 04:03 PM
Everytime you go up in a plane -- even a passenger airliner -- you're putting your life in someone else's hands.

You're placing your life in the hands of of, occasionally, disgruntled aircraft mechanics or over-worked ATC's and the only protection you have is tonnes and tonnes of government regulations, drafted by other disgruntled government employees, many of whom aren't pilots, that you hope they follow.

The aircraft industry is stagnant. Concorde is dead, the "new designs" coming out of Boeing and Airbus are just larger re-hashes of 30-40 year old designs.

GA is even worse -- there hasn't been a significant innovation in GA design for 35 years. Cirrus is a nice, old design, with new materials, but at $400,000 a pop, not many of us will be flying them soon.

In comes the Kit Plane industry -- Innovation, intelligence, ingenuity and affordability. And, all it asks in return is that we take personal resonsibility for our choices. No lawyers, just men, women and their minds -- and, in some cases, their bodies. The Kit Plane industry will save GA from itself -- if we can keep it free.

We are ALL going to have to make tough decisions about our powerplants in the not to distant future when 100LL is no longer availiable -- that is not an "if", it's a "when". Lycoming and Continental aren't telling us what plans they have, if any.

There are a few alternatives on the horizon down the certified path, Wilksh, SMA, Centurion -- all expensive and all unproven by large statistical samples.

Automobile engines are, for many reasons, superior in all ways (performance, reliablity, economy) to the 40 year old designs coming out of Lycoming and Continental. Automobile conversions have not, traditionally, been very successful. Mostly because conversion were undertaken not to provide superior performance, but to provide a "cheap" alternative to certified engines.

There are engineers out there now, who are creating high-quality, high performance, but not necessarily lower-cost conversions that, in at least one case, have been achieving their goals.

Everyman has to make his own decision on what risk he's willing to take. You do the research, you talk to the engineers (When was the last time you got the lead engineer from Lycoming on the phone?), talk to those flying the engines, get the data -- then use your own brain and make a decision.

There is a movie, based on a famous book, called "The Fountainhead". A brilliant architect, named Howard Roarke, designed buildings based on new materials and new technologies. He refused to make them look more safe and familiar by incorporating useless classical additions. Everyone said his building would fall, that they were unsafe, but they stood and were magnificent.

No one will deride you for taking the safe, certified path -- and many will deride you if you take the Howard Roarke path. But ultitmately, it's a personal decision. You have to ask yourself, why are you flying a kit plane instead of a certified Cessna 150?

bhassel
01-20-2005, 08:54 PM
Actually the newer model eSubie's (Eggenfellner) are new engines, not used engines.

There are advantages and disadvantages in going with either the eSubie's or the Lycosaurus. The eSubies can provide real heat to the cockpit. There is reduced complexity in the cockpit with no mixture controls to worry with or prop controls either. Then there is the easy installation; hooked up and runnng in a day or less (plug and play). You also have the option of boosting with a supercharger to maintain power at higher altitudes.

$ for $ even if the eSubie's may be comparable in price they do offer some advantages that the Lycosaurus does not.

In the end I may very well use a cheap used Lyco. But it'll be just because of the lower up front costs. That doesn't mean I believe it's actually the best solution.

Now if I could afford a new lyco then I'd be hard pressed not to get an eSubie instead!

f1rocket
01-21-2005, 08:08 AM
Oh boy, where do I start.

Automobile engines may be of a higher technical level than a Lycoming, but they are NOT superior when it comes to driving an airplane through the sky. Take a look at the main crank bearings and the engine block of a Subaru and compare them to the Lyc. When you are swinging the weight of the prop out front, it requires some hefty support. Lyc's also deliver peak power at low RPM, while the Subies need to scream along at much high RPM to deliver peak horsepower, hence the gear reduction units. I contend that automobile engines are very poor airplane engines because they need to be jerryrigged to make them work.

The benefit they have is that they are cheap because they are mass produced. Can't beat that. They also have great reliability when used for their intended and designed use. Start sticking them in airplanes and you are bringing along a whole additional set of engineering problems to be solved. I don't know any engine engineer that thinks gear reduction units are the best way to turn a prop. No, it's just a band-aide stuck on an engineering problem that otherwise, can't be fixed.

The whole 100LL thing has become the enabling battle cry of the alternate engine groupies. Unfortunately, it doesn't hold water. No one is going to wake up one moring to find that hundreds of thousands of engines that use the product suddenly are silent because no one is making it any longer. I don't doubt that there will be a transition to other fuels in the long run. That's probably why the diesel engine is looking like a viable engine alternative. But you and I will be able to buy 100LL for many, many years to come. Now the price of that gallon of 100LL may be another issue.

Finally, the reason I fly a homebuilt and not a Cessna 150 is because I can upgrade my Lycosaur with electronic ignition, FADEC, etc and get the best of both worlds----newer features and capabilities with proven reliability.

Tom Maxwell
01-21-2005, 08:27 PM
This is a good thread and I am surprised that others haven't chimed in by now. I am not an engineer so I cannot provide objective data, frankly I haven't seen a comparison, but here are my thoughts, whatever they are worth.

Automobile engines may be of a higher technical level than a Lycoming, but they are NOT superior when it comes to driving an airplane through the sky.

Maybe not superior but I don't feel they need to be considered inferior either. They are the product of years and years and years of engineering by some of the best engineers in the world and by companies with very deep pockets. They are outstanding machines and I see no data to suggest they are inferior when it comes to moving an airplane.

Take a look at the main crank bearings and the engine block of a Subaru and compare them to the Lyc. When you are swinging the weight of the prop out front, it requires some hefty support.

Agreed, it does take support. But just looking at the physical size of the bearings is not all that needs to be considered. The Subaru has more bearings and they are spaced much more closely together. This provides for a great deal of support and also makes for a smooth running engine capable of very high RPMs. In addition, PSRUs actually help provide support and also isolate the engine crank from a lot of abuse. Finally, combine these super smooth running engines with a well balanced lightweight prop and a lot of the abuse is eliminated. I agree that with all else being equal (which it isn't) a Lyc would seem to be the sturdier of the two, but when the entire package is considered, the auto engines actually punish the components and the airframe less and therefore may even be superior.

Lyc's also deliver peak power at low RPM, while the Subies need to scream along at much high RPM to deliver peak horsepower, hence the gear reduction units. I contend that automobile engines are very poor airplane engines because they need to be jerryrigged to make them work.

Yes and no. Yes they do run at high RPMs, they are designed to run at high RPMs. This is not in itself a negative. Running an engine at 3500-5000 RPM that can run easily at 7-8K is not a big deal. I don't view a PSRU as a "jerryrig," we have been using geared units on cars for decades (we call them transmissions and differentials) and they seem to work pretty darn well. Sure it is another point of possible failure, but the history is pretty good on them so far. Granted they don't have the history of the Lyc but they seem to be pretty good non the less.


The benefit they have is that they are cheap because they are mass produced. Can't beat that. They also have great reliability when used for their intended and designed use. Start sticking them in airplanes and you are bringing along a whole additional set of engineering problems to be solved. I don't know any engine engineer that thinks gear reduction units are the best way to turn a prop. No, it's just a band-aide stuck on an engineering problem that otherwise, can't be fixed.

Yes the auto engines certainly are more economical and they are very reliable. Although the initial cost is about the same, this is more a result of the number of suppliers and engineering start up costs. These costs will come down as more are produced and FWF packages are finalized. But even at current costs the fuel cost savings of a conversion over the life of the plane will be very significant. Yes resell costs may be lower, but then again, maybe not 10 years from now. But who cares? If you plan to sell your plane in a year or two it may make a difference, but if you plan to fly it for 8-10-12 years or more, you make up that difference in fuel costs alone. Run the engine out and if the buyer wants a Lyc 10 years from now, let him strap one on and go. I don't agree with the "bandaide" reference. It implies a temporary fix to something that is broken. Sure the conversions are a different solution, but I don't see any evidence to support that they are a broken or substandard solution. I guess I will take your word on the engineer comments, I have not seen any polls on the issue. I am curious about how many engineers you have queried and why they feel a PSRU is not a viable solution.

The whole 100LL thing has become the enabling battle cry of the alternate engine groupies. Unfortunately, it doesn't hold water. No one is going to wake up one moring to find that hundreds of thousands of engines that use the product suddenly are silent because no one is making it any longer. I don't doubt that there will be a transition to other fuels in the long run. That's probably why the diesel engine is looking like a viable engine alternative. But you and I will be able to buy 100LL for many, many years to come. Now the price of that gallon of 100LL may be another issue.
Finally, the reason I fly a homebuilt and not a Cessna 150 is because I can upgrade my Lycosaur with electronic ignition, FADEC, etc and get the best of both worlds----newer features and capabilities with proven reliability.[/QUOTE]

Maybe yes maybe no. While there doesn't appear to be any indications of a shortage of 100LL anytime soon, we just don't know what the future will bring. You state that we will be able to buy 100LL for many, many years to come. I am not sure how you have reached this conclusion, I don't see any evidence to know one way or the other. I think we all agree that there is some pressure on 100LL. What that pressure will bring or how long it will take is not known but I suspect that it will not result in better availability or lower prices in the future. As far as EE, Fadec, etc. these are certainly not advantages over an auto conversion. The auto engines were designed with these features in mind from the ground up. I guarantee that GM and Subaru have put tons of more money into engine control research than all of the FADEC suppliers put together. I think it could be argued that adding FADEC to a Lycomming is a bandaide approach to engineering compared to the auto engines that were designed from the ground up with them in mind.

The biggest advantage I see to a Lyc is simply availability. They are available everywhere. Parts are readily available amd you can get them worked on at almost any airport. You can buy auto engine parts off the shelf but finding FWF parts for them at remote airports and finding someone to put them in for you might be a challenge. This will change as more and more become in use. Hey at one time I bet finding Lyc parts and someone to work on them was tough also.

The biggest advantages I see to conversions is that they represent the latest and very best in engineering, they are water cooled and they run super super smoothly. I hear people talk about a smooth running Lyc but compare it to the audio on Jans web site of the Subaru and then tell me in good conscience that a Lyc runs smoothly.

I compare the Lyc to a Subaru as a Harley to a Gold Wing. They will both get your down the road. The Harley has a cool factor to it and its long heavy stroke creates a not so smooth ride. The Gold Wing, on the other hand, may not be as cool or may not have been around as long, but it will get you where you want to go using the latest in engineering technology and it purrs like a kitten.

Bottom line is they will both get you to your destination and pretty darn well. Some like the features of the new engines and the excitement of trying new technology, some are more comfortable with the proven Lyc. To each his own.

N916K
01-21-2005, 09:19 PM
I was really interested in the subject a few years back. I wanted to believe that a modern car engine was better. It didn't really take long to come to a conclusion once I really thought about it.

First of all I work as a vehicle dynamics engineer in the auto industry. I'm out every day pounding cars on the test track. One thing is very clear when you are driving a car at 100% all day (most people only drive at a small percentage of that, eventhough they may believe they drive around fast). Not all engines and transmissions are the same. They are built with specific jobs to do. For example, the Toyota V6 gas engine is a great car engine. When they stick it in the 4Runner it's a real piece of junk, the torque is way up high, you can't pull up a hill at all unless you slip the clutch. It was not made for that application so it fails at being a truck motor. Take a look at the Ford 6.0 Deisel, they are a great truck engine. Really stink for soccor moms driving kids around town. Drivability is very poor compared to a quick responding gas motor.

The point is, airplane engines are basically generators. They cruise along at a constant speed, don't require any transients. Except for a couple of deisel truck engines, the typical car engine just isn't made for that. Even a Vette motor can't take high speeds for more than a minute or so. (Before I get a bunch of bowtie poeple yelling at me, I've broken more vettes on a track that you can imagine) And all those Honda, Nissan, Toyota, Subaru guys, yes they have all been towed off the track with broken motors from sustained high engine speeds.

So in conclusion I chose to go with an airplane engine. You enjoy whatever engine you pick and I wish everyone a great time flying their plane. Just please stop argueing that a car engine is made for sustained high engine speeds and power, it just isn't. They are made to make soccor moms and Uncle Sam happy not to power generators.

Kevin Horton
01-21-2005, 09:23 PM
Maybe not superior but I don't feel they need to be considered inferior either. They are the product of years and years and years of engineering by some of the best engineers in the world and by companies with very deep pockets. They are outstanding machines and I see no data to suggest they are inferior when it comes to moving an airplane.


The biggest advantages I see to conversions is that they represent the latest and very best in engineering, they are water cooled and they run super super smoothly. I hear people talk about a smooth running Lyc but compare it to the audio on Jans web site of the Subaru and then tell me in good conscience that a Lyc runs smoothly.


We need to make a very clear distinction between the engine core, supplied by the automobile manufacturer, and all the essential accessories and mods that are required to create an aviation powerplant.

The automotive engine core is likely very well engineered, and may be extremely reliable, even when used in a different mission than it was designed for. But, every automotive conversion I have seen had a number of essential items that were either designed by the builder or the conversion manufacturer (e.g. reduction drive, cooling system, fuel delivery system, etc.). These essential accessories are not nearly as well engineered as the engine core, yet a failure of one of them has the same effect as a failure of the engine core. For example, a local RV-7A builder had an engine failure (one of the more popular automotive conversions that is touted as running very smoothly) that was due to vapour lock due to a design problem in the firewall forward kit. The conversion manufacturer acknowledged a design problem, and later provided a modified part. The builder sold the aircraft, and is building a new one, which will have a Lycoming. I am aware of an Mazda rotary powered RV that had an engine failure due to a problem with the builder installed carburetor. Another RV had an engine failure when the supercharger belt came off in flight.

So, don't think that the "superior" engineering of the engine core necessarily translates into higher reliability than you would get with a Lycoming. If you want to install an automotive conversion, it's your aircraft, do what you want. But please don't kid yourself that you are doing it to get higher reliability.

Tom Maxwell
01-21-2005, 10:23 PM
I agree, the whole package needs to be considered. These conversions are pretty new and with any new endeavor there are going to be start-up issues and engineering issues to resolve. Although I am much to young to know ;) , I think there must have been issues with the first Lycomming engines as well. There are probably some on these boards who can tell a few stories about early Lycomming engines.

Things do happen with machines, no question. The examples you cite seem to me to be problems that could have happened with Lycommings as well. I've heard stories about vapor lock and carb problems on Lycommings and I guess it isn't to far fetched to believe that a belt could break on a Lycomming supercharger. One of the first RVs I saw "live" was under repair following a forced landing. In talking to the owner, he said that a bearing had frozen and the piston rod twisted off. I guess what I am saying is that yes stuff does happen and it isn't limited to new packages. Frequently, the failures are not with the core engines at all but with the supporting equipment. I would expect to see more issues with these new package than with Lycomming packages and I expect the new packages to improve over time. Only time will really tell if these packages are realiable and if they are good alternative. I am sure there are thousands of Lycs flying and they have been for 30 years. In perpective I think Jan has 300+ Subies flying with only a few years of experience. We will see where it all leads.

I will definitely concede that a Lycomming is a proven workhorse and a safe choice. Much like choosing IBM in the 70's and 80's. I once had an executive tell me, "IBM may not be the best solution, but I won't get fired for choosing IBM." Today choosing an IBM alternative is not considered risky at all. I understand that everyone has different comfort levels, so to each his own. I fault nobody for not jumping on the wagon or for waiting until the new packages get more time and become more proven. Some will elect to be a part of the journey and others will sit back and watch, and that is OK.

What do you think about the Lyc alternatives. Are they better or just-as-good or do they have issues that make pure Lycommings better?

As I said, I am not an engineer so I do appreciate the engineering perspective and your thoughts. Thanks for you input. I would be interested in hearing what the failures were in the auto engines after running them for long periods of time at high speed and how the engines might be improved to handle it. Or is the only answer to piston powered flight a long, hard, slow stroke and lots of beef to handle it?

Thanks again for the discussion.

Highflight
01-22-2005, 06:41 AM
What do you think about the Lyc alternatives. Are they better or just-as-good or do they have issues that make pure Lycommings better?



A couple of weeks ago, the differences between how Lycomings are built and the things that are different when building the same base design but by different companies (Superior and Mattituck) were posted on the Lycoming Yahoo group.
There's a good handful of improvements that the two other builders have done to their engines and they all make lot's of sense.

Are they better than the Lycoming brand?... I don't know, but the improvements do seem to be geared toward dependability and durability issues so the answer is; maybe and/or probably if the improvements really DO add dependability or durability to the basic design .

And something else that should be said about the "60 year old design" still built by Lycoming and now the same design used by other companies is that there have been major advancements in the areas of metallurgy and other areas of engine design that weren't around 60 years ago.
Those advancements give us things like Nikosil lined cylinders, flow control for smoother running, and better implementation of internal oil dispersion and stuff like that. Those things, as basic as they are today, were not likely incorporated to any great degree in the original Lycoming design.

So perhaps the Subie and Mazda fans might consider that the basic mechanical design of the "old" Lycoming type engine, coupled with modern materials and engineering of things not even thought of 60 years ago, make the Lycoming a better and more reliable choice than the car engine people like to think.

Vern
RV7-A

Darrell514
01-24-2005, 10:43 PM
I don't know the reason other people want an alternate engine over Lycomings but the reason i do is smoothness. It doesn't mater how much modern materiel you put in it is still going to be a big bore strong pulse thumper.You can't make a Gold wing out of a Harley. I presently fly a Kitfox with the Rotex 912 and have had a lote of comments on how smooth it is compared to Lycs. I don't know if i will go with a auto converson,probably the Deltahawk if it works out but not a Lycoming :mad: unless they are giving them away.Once you've flown smooth you will never go back.The airplane might like you better to :)

Darrell RV9A

Rotary10-RV
01-26-2005, 01:36 AM
Ok group,
The real need is to determine how an engine was designed to be used. I'll try to be brief. Orrenda proved that parts availability isn't everything when 40 mil was spent trying to build a Small-block airchevy. The auto V8 has a lot of problems, (like bearing area) when converted to aircraft use. Even the mighty Japanese giant Toyota gave up on it's Lexus based V8. No takers with the 400 hour TBO! Some engines are better than others for conversion. The Little Subie with a 5 main bearing bottom end is much better suited to 100% operation. When properly mated to a good PSRU it shines. Don't forget that engines like the RR Merlin were gear reduced, likewise many of the large radials. I plan to use a rotary (Wankel) in my RV-10. The rotary probably makes a better airplane than car engine. The devil is in the details, Mistral of Switzerland and Florida are certifying a rotary. The biggest problems are in the ancillary systems, can you use the auto injection and engine management systems? Can you design a good redundant system? Like the argument about steam gages or an all electric panel arguements can be made for both sides. If you aren't capable of doing some of the design work yourself you should probably stay away from conversions. You need the skills even if you buy the package to determine if the seller knows what he's talking about. If you are up for that challenge then good carefull design will produce a good flying plane.
Bill Jepson

gmcjetpilot
01-27-2005, 07:45 PM
Darrell514: "I presently fly a Kitfox with the Rotex 912 and have had a lote of comments on how smooth it is compared to Lycs."
There is a big difference between 80HP and 180HP.

Tom Maxwell: "The biggest advantage I see to a Lyc is simply availability."
Absolutely, just about any airport you land at with service will have a mechanic that is familiar with Lycs and have tools and parts for them. Yes there are many car dealers but not on the ramp of airports. That is why autoengine RV?s may not have as good resale. People who buy 2nd hand RV?s will not likely be as apt to work on them nor can they legally do more than part 43 appendix A. Getting a local A&P or AI to work on your Eggen RV, because of lack of familiarity, parts and liability may be a problem.

F1rocket: "Finally, the reason I fly a homebuilt and not a Cessna 150 is because I can upgrade my Lycosaur with electronic ignition, FADEC, etc and get the best of both worlds----newer features and capabilities with proven reliability."
Absolutely, A Lyc has choice of several electronic ignitions, fuel injection, FADEC, exhaust systems and many fixed and constant speed Props. Auto conversions are limited to single supplier for parts. As far as props, the auto engines use fixed or (EXPENSIVE) electric propellers. I?ll just say electric props with slip-rings and brushes, some with ultra-light pedigrees are not in the same league with hydraulic controlled props. In my opinion Hyd beats any Elect prop in maintenance, reliability and control. Hydraulic props have decades of experience and testing. With an electric prop, you are the test pilot. With a fixed prop the Subie takes a further hit in performance because it needs the RPM for power.

F1rocket: "Automobile engines may be of a higher technical level than a Lycoming, but they are NOT superior when it comes to driving an airplane through the sky."
Absolutely, people have the idea that Lyc's are stamped out by a Black Smith with a hammer, anvil and an open fire. They use state of art CNC, materials, processes, tolerances and manufacturing controls..

bhassel: "Actually the newer model eSubie's (Eggenfellner) are new engines, not used engines."
Uhaa, You can buy a brand new O-320 fixed prop, outright from Aerosport or 6 other places for $18,500, with all the accessories. You bolt it the engine mount that came in Van?s kit, add a $2000 fixed prop, one or two grand for exhaust and other stuff and be done. What does an Eggenfellner cost? About 30-40 Grand by the time you buy everything including prop ($8K). I would say the fixed prop O-320 will out perform the normally aspirated Eggen and be lighter by 50-100lbs. The Cost advantage of the bolt on alternate engine kits are an illusion.

Bhassel: "The eSubies can provide real heat to the cockpit."
Uhaa I have a heat muff. Aircraft Exhaust Technologies, Inc made my exhaust. They welded little ?heat studs? like a porcupine on the pipe where the muff wraps around the pipe. I can roast marsh-mallows with it.

Bhassel "There is reduced complexity in the cockpit with no mixture controls to worry with or prop controls either. Then there is the easy installation; hooked up and running in a day or less (plug and play)."
I understand the idea of a single lever control like a jet, but really is this a big burden? I don't find it a problem moving the throttle, mixture and prop cont'ls. I have seen Subie engine installations and they look more complex than a Lycoming to me. I think you can run a Lyc with two wires, three push-pull cables and a fuel line. No redundant electric fuel pumps, electric water pumps, dual electrics-batteries, water hoses and radiators. Plug and Play and Play and Play A-lot. I say if you want to fly and not tinker, use a Lycoming per Van?s plans.

Bhassel: "u also have the option of boosting with a supercharger to maintain power at higher altitudes."
Uhaa, You also have the same option with a Lycoming, and your point?..
I agree you can get more performance at high altitudes with a turbo charger. You will be sucking O2 thru a mask to use it; you have to go to 12-13 grand to see the turbo benefit. A Gent in Canada made what I think is an exemplary Custom Subie installation with a turbo. Well designed, tested and built. A fly off between two RV-6A?s, his Turbo Subie and a 180HP Lyc powered one, gave a slight edge to the Lyc until about 12K feet. At 12k the turbo Subie had 1-3 Kts and a little more fuel burn over the Lyc. (No free Lunch.) That is pretty good for an engine with 1/2 the displacment, but of course he needed 35" boost & 4800RPM get the job done. This was NOT an Eggen installation but a custom design. The builder clearly has more ability and resources than most builders do, including me. You want to go fly, bolt on a Lycoming. You want to invent and design and tinker, by all means build your own installation.

Bhassel: "Now if I could afford a new Lyco then I'd be hard pressed not to get an eSubie instead!"
Bob, price it out. Look at the prop, the kit the real cost of Egg or whoever kit you buy. Than look at a Lycoming, I don?t see a big cost savings. Now if you are going to roll your own Subie or better a Rotary with ?Real World Solutions.? That is a different story. We are now talking sweat equity. Again fly or tinker, your choice. You still may end up with something that is heaver, slower and not that much cheaper.


Fredmoss: "Every time you go up in a plane -- even a passenger airliner -- you're putting your life in someone else's hands."
What does it have to do with Auto engines in airplanes?
It is 4 times safer to fly on an airliner than to drive.
It is 26 times safer to drive than fly in a general aviation private plane.
It is 104 times safer to fly an airliner than fly in a general aviation private plane.

Fredmoss Automobile conversions have not, traditionally, been very successful. Mostly because conversion were undertaken not to provide superior performance, but to provide a "cheap" alternative to certified engines.
"Automobile conversions have not been successful in improving performance because there is no Free lunch. They are limited by the same physics as any engine. Typ alternate engine installed real weights are more, they have less ?real? HP at the prop and burn as much or more fuel per HP. The fastest RV's still have Lycs." :D

Subie is an internal combustion 4 stroke, overhead valves & cams, water-cooled auto engine. No quantum leap in technology here. Auto engine electronics are for fuel economy and emissions, where you go form idle to max load, back to low power over and over. Electronic technology for airplanes is available and works, but the advantige in an aircraft is not as great as for cars. The Lycoming, does not need overhead cams or water cooling. It is a light weight, low RPM, high torque, air-cooled engine for an airplane, designed to direct drive a prop at steady RPM. Water cooling is better in controlling cylinder piston tolerance which improves emissions. Lycs don't have emission requirements. Look at the real empty weights of finished RV's with a Subie. They weigh the same or more than a typical 200hp Lycoming (which are heavy) with a Hartzell constant speed prop, but the actual performance is more like a 150/160hp Lyc.

The Mazda seems to be a better choice of the ?alternative engines.? The Mazda has it?s own set of rules. Go to the Guru of rotary, Tracy?s Real World Solutions. http://www.rotaryaviation.com/ For someone who sells rotary engine conversion components, he is about as fair, rational and honest about this alternative engine as anyone. PLUS most important he actually fly?s his product. ;) If I wanted to tinker and might save a little money in the process, go with the Rotary. I don?t. That is why I have a Lycoming O-360. As far as money I bought a core, overhauled it with new parts and ended up spending about $10-11K on the engine/carb."


Cheers George :D

atreff
01-28-2005, 12:15 PM
To me, any questions I had about the suitability of using automotive engines in Aircraft was answered four years ago in an article that appeared in Sport Aviation. It was a feature on Jim Rahm's beautiful 420HP Lancair IV. Jim used a V-8 designed and build by Al Joniec, a veteran NASCAR guru. The first thing that Al said was he had spent his automotive career trying to get Detroit steel to run at 100%+ power on race tracks. The problem, he stated was because auto engines rarely are run at 65% power. They spend their time much lower power settings. At highway speeds, they are putting out 17-22%, depending on the gear train and automaker. During a jackrabbit start, 100% is for a few seconds, and as higher gears are selected, the engine is below 50% rapidly. Asking a stock auto powerplant to sustain 100% power for climb then 75% in cruise was an exercise in accelerated life testing, according to Al. For Jim's Lancair, I believe he chose a Chevy boat racing engine lower end, due to the sustained high power output demanded by power boat racers.

I agree that auto engineers are pushing the electronic envelope in ignition and fuel systems, and that's great. I wish Lyc and Cont. would follow suit. The reliability of modern electronics keeps getting better and better, which is why we have so many radio options now avialable to us.

However, for me, the 'rubber meets the road' on the durability of autoengines question. They are not designed to run a long time at over 50% power. That cinches it for me, water cooled or not, electronic ignition or not, better cabin heat or not, single power lever or not. If the crank, case and bearings are not going to hold together for 2000 hours running at 65%+, it's not the engine for me. I think that the post by the gent who tests cars for a living bears this statement out.

That being said, I encourage all of us to fly what we like best, and to enjoy it fully. For my mission, which is reliable long distance IFR transportation, I'm installing a Lyc. I've got 2200 hrs flying behind one and it's never let me down or left me stranded....

Tom Maxwell
01-28-2005, 01:51 PM
I guess a big issue in trying to argue on behalf of conversion packages is there just isn't enough information or history to support it. It is pretty easy to argue the history and peformance of the Lycs and Lyc-a-likes but not so for the conversions.

There are a significant number of people who argue that auto engines are not engineered for this kid of abuse. I guess those of us who are not engineers and do not know what "engineered for aviation use" vs "engineered for auto use" really means will have to take their words on it, and it may well be true. But there is another group of individuals who feel differently and are forging ahead and trying these alternative solutions. Can't really fault them for that either. This group seems to believe that the auto engines are more than capable of being a reliable source of aviation power. Only time will tell for sure.

I think the Egg package is probably the most well known and most prolific of all the conversions. While the firewall forward package does create some very exciting challenges, I think those leaders in this arena are pounding out good solutions and finding better solutions every day. One of the reasons I think Jan is being successful is that he does look at the entire package and he isn't just throwing an engine out there and leaving the rest to others. He is constantly looking for better ways to do it. Some like being on this leading or bleeding edge, others are not comfortable with it. There are getting to be a significant number of flying Eggs and they are starting to rack up some hours. Again, I don't have hard numbers but I think there are a few Eggs near 1000 hours and I am being told there has never been an engine or PSRU failure. Supporters see the smooth operation, lower fuel costs, and lower overhaul costs to be very appealing. Again, whether these all pan out will be proven over time.

Someone has pointed out that there have been failures in planes carrying these engines, but I believe the examples given were belts, alternators, and other peripheral failures and not engine failures. Nit-Picing? Maybe. But there are a lot of documented examples of peripheral failures on Lyc packages as well. Take a look at Rosie's post on cost of ownership as an example. Nothing on the engine, but several peripheral issues. The bottom line is that if we hang it on the engine, it will be a potential source of failure. Peripheral failures are going to happen and are not a reflection of the quality of the engine to which they are attached.

I have really enjoyed everyone's input on this and I hope others have as well. There are definitely pros and cons to staying with the tried and true and there are pros and cons to venturing off into new territory. I don't see that there is a clear winner either way, but each of us will have to weigh what we believe to be the key decision points and go from there. To be forthright, I don't know which way I will go when the decision finally comes. I don't know enough about them yet to make my decision. I have always been kind of contrarian in everything I do, though, so that may play into my decision. If it doesn't work out either way, hey it is only a $25K to $35K mistake and we have already determined that when it comes to flying money is no object. :D Just kidding!

If nothing else, I believe there is a need for competition in this market. I am excited to see alternatives come and go and think the effort will make for a more competitive and better market for all of us. You can bet the Lyc and Lyc-a-like manufacturers are not just sitting on their hands watching this happen. Competition only makes for more cost effective and better engines all around.

Thanks again for the input. It has been very beneficial to this neophyte.

f1rocket
02-01-2005, 11:56 AM
Tom,

I thought you did a nice job of summarizing the discussion and bringing it full circle hence the title "Are you Ready to be a Test Pilot?". That was my whole point in starting this thread. It wasn't to trash the ideas of the alternative engine builders, although their ideas are not for me. It was to get folks to consider the fact that if you strap one of these on your bird, you are truly a "test pilot", perhaps more so than these engine providers would lead you to believe.

The entire engine package does not have the benefit of thousands of hours of actual flight time, so you are helping to establish the engine's reputation, rather than relying upon it. That doesn't make it bad or good, and I realize that there's no way for the alterntive engine folks to overcome it until more time is built up, so time will tell. I hope they do prove to be an economical alternative because everyone in aviation will benefit from it if they do.

I still don't believe today that the engineering data, acquisition cost, maintenance cost, resale value, performance, or reliability make the Subie a better powerplant than the Lycoming, but I'm okay if others want to believe it. Just temper the exhuberence with some tought questions and open eyes, and if it still make you smile, then go for it. Most of all, enjoy the hobby and be safe.

Tom Maxwell
02-01-2005, 01:34 PM
Yes indeed, I agree 100%. I think the cost of the alternative packages is somewhat of a stickler. When a full package can be had for 50%-75% of the cost of a Lyc. then the risks are somewhat mitigated and we po folks are a little easier to sway. When the cost of a package is equal to or more than a Lyc. it makes the decision a whole lot more difficult. In the end I will probably go with my gut feel. Although I love the idea of a super-smooth Suburu, something just doesn't sound quite right about running an engine at 4k RPM for extended periods of time. Time will tell and I may be swayed yet.

Of course you guys driving the rockets with the big gas guzzling 540's in them don't care about money ;). So you guys should be leading the way and trying all of these new options so we po folks will have more data from which to make our decisions. Just kidding!

Thanks for the thread. It has been very informative for me.

Build9A
02-01-2005, 01:39 PM
I figured that I would chime in here on a minor point, but one that was significant for me in the lyc vs conversion discussion. When I was considering the lyc vs conversion I weighed the ease of installation issue. Being a novice I was attracted to the plug and play approach which was advertised by some of the conversion options. I have no evidence of how simple the conversion installations are, but have no reason to doubt their claims. However, in my case I purchased a lycoming 0-320 D1A from Vans and their firewall forward kit. You bolt the engine on the mount, wire and plumb per the plans. The plans are simple and the most straight forward of all the Vans dwgs. IMHO. There were a few minor wire routing and securing questions that my tech guy helped with. Otherwise, it couldn't have been simpler. It was one of the most satisfying parts of the building process. And I am a pure novice. I had an A&P AI check it out and he made only one suggestion. He also said "where did you get that exhaust?, it's a great set-up". Jack RV9A, ready to schedule DAR.

f1rocket
02-02-2005, 08:36 AM
Of course you guys driving the rockets with the big gas guzzling 540's in them don't care about money ;). So you guys should be leading the way and trying all of these new options so we po folks will have more data from which to make our decisions. Just kidding!
Common misperception. The IO-540 actually only guzzles more gas if the Go Lever is pushed all the way forward (not often). It would probably surprise most people to learn that the IO-540 is as fuel efficient as it's smaller cousins at typical cruise settings. However, if you want to go really fast, it will drink the well dry in no time.

RudiGreyling
02-03-2005, 01:14 AM
Wow guys very good discusion/debate, keep it up, us newbies are learning a lot... :D

Scott DellAngelo
02-24-2005, 10:57 AM
My $0.02. Hu

xm15e3
02-24-2005, 02:03 PM
I don't know any engine engineer that thinks gear reduction units are the best way to turn a prop. No, it's just a band-aide stuck on an engineering problem that otherwise, can't be fixed.


Maybe not for simplicity, however every liquid cooled aircraft engine from WWII, and all of the radials bigger than the R985 have PSRUs. HP=TxRPM/3300, more RPM, more power and at a certain point more better power to weight. I agree with you, but I wouldn't denograte them all as bandaid fixes. I still wouldn't buy anything with a G0-anything even if I could afford it.

IMO, I wouldn't consider a auto-conversion for any reason. As mentioned above, cost/benifit never seems to balance. However, for engines over 300-400hp there seems to be a place for custom built, automotive based engines such as the Donovan/KeithBlack/Falconer that are built for 700hp, but severily detuned to operate around 400hp continous. Think more like a marine engine than an auto engine. I still wouldn't do this for cost reasons, but only because I think 0-720s suck, and an MP-14 or 985 might not fit.

RV6_flyer
03-24-2005, 09:49 PM
I wonder if the Subie guy you know is the same one I know that also had 3 forced landings. One on takeoff at my airport. One was on a road on the way to Oshkosh 2004. Fixed it on the road, took off on the road, and then flew to Oshkosh Airventure 2004. One was over an airport on the way home from Oshkosh as he was over the airport when the problem happened.

The story goes on my airport is that two more forced landings and he is an ACE.

Gary
CCB in SoCAL
RV-6 1,644 hours flying, O-320 (4,882 TT engine), Hartzell Prop

My $0.02.

SNIP

I know on very good source (someone who knows and flys with the guy) that one of the biggest Subie supporters has had multiple (yes multiple) forced landings, at least one of which was off field. Another was on takeoff. Don't email me asking who because if he isn't saying anything (i've never seen anything about it) then he probably doesn't want people to know so I won't be the one to spill it. I will say that the guy who told me had no reason to lie to me and seemed to know the details very well.

I respect the guys who try it, don't get me wrong, but no way was/is one going of the front of my RV. Instead I got a used Lyc that I am overhaulling myself and should be WELL below the cost of any other option and be freshly overhaulled.

Scott
#90598 Fuselage (making no progress with the current state of my shoulder :( )
:D

Radomir
03-25-2005, 12:48 AM
ok guys, now you're giving it away :)

on a more serious note, and all joking about being an ace aside, this is quite concerning. This is not a sport to test your luck in... you'll be disappointed how quickly it runs out.

PS. to reflect on one of Tom's posts -- on contrary, the pricing of soobie packages made this decision a total no brainer. I'm only afraid I would have been tempted to consider an alternative if it was 50-60% cheaper.. but with these numbers, it's really easy to make that decision.

leeschaumberg
04-29-2005, 07:40 PM
The aircraft engines of today have been around since WW2. Some people use antique automobile engines. Some people use rotary engines ,noisy but high fuel flow and smooth. And some use higher tech auto engines.
After many dyno runs (nearly 5000) it becomes obvious what works and what doesn't. There are many requirements of a good aircraft engine. Stated below are some of them.
1. Smooth internal combustion engine. Smooth is a flat 4, flat 6, inline 6, vee 12 . Turbine engines (external combustion engines are too costly) are not used in light aircraft.
2. Low fuel consumption of an economical fuel.
3. Proven long life
Under 1. of above an inline 4 , V6 , V8 , doesn't make it. No matter whats done the engine doesn't make it. Anyone that has read an engineering manual can tell you. If some one tells you that they got it to work is lying to you. Rotary engines are very smooth but thier fuel consumption suffers.
Under 2. Because aircraft have to carry all the fuel to burn , a low fuel consumption means a lower gross weight and all the benefits of this. An economical fuel don't mean LL100 that sells for more than $4.00 a gallon in the United States. A maximum fuel flow that is low is good. (BSFC) brake specific fuel consumption is used. The units of measure are pounds of fuel per horsepower hour.
Under 3. Here the typical aircraft engine is the winner. But we can't sit on our back sides and say or do nothing.
So you can see that a usable aircraft power plant is not some thing available anywhere. The alternative to the old reliable may not be good.
Lee

leeschaumberg
04-30-2005, 05:31 AM
A modern and good aircraft engine would be the following:
Liquid cooled - Air cooled engines suffer from being too cool and to hot. Liquid cooling would maintain the temperature no matter if your climbing or desending. A good engine temperature to maintain is 180 - 200 degrees f .
A flat four. Naturaly perfect balance and fit in the existing airframes.
200 hp - This horsepower is what people are looking for and it would provide the desired cruise speeds, take off distances, and climb performance.
Engine would run on light oil. No. 1 or 2 diesel , JP4 , Biodiesel. This would make an ignition system totally unneeded . The fuel cost would be lower and the emmisions would also be lower.
4 cycle diesels are very heavy. A good long lived 2 cycle diesel has been in use for a very long time. The 2 cycle Detriot Diesel model 53. Supercharging is needed to start. At altitude the air becomes less dense (lower pressure) and a compresser is needed anyway. The two speed supercharger ( not turbocharger ) first apeared in WW2. So starting and flying at altitude would be easy.
With these thoughts in mind you could net an engine with the following specs:
200 hp at 2800 RPM Normalized to 20,000 feet.
Engine weight that is very comparable to an IO360.
Engine life around 4000 hours.
An electric preheater would make the engine usable in any climate.
This sounds like a dream but very easy and do able.
Lee

PJSeipel
04-30-2005, 07:44 AM
A modern and good aircraft engine would be the following:
Liquid cooled - Air cooled engines suffer from being too cool and to hot. Liquid cooling would maintain the temperature no matter if your climbing or desending. A good engine temperature to maintain is 180 - 200 degrees f .
A flat four. Naturaly perfect balance and fit in the existing airframes.
200 hp - This horsepower is what people are looking for and it would provide the desired cruise speeds, take off distances, and climb performance.
Engine would run on light oil. No. 1 or 2 diesel , JP4 , Biodiesel. This would make an ignition system totally unneeded . The fuel cost would be lower and the emmisions would also be lower.
4 cycle diesels are very heavy. A good long lived 2 cycle diesel has been in use for a very long time. The 2 cycle Detriot Diesel model 53. Supercharging is needed to start. At altitude the air becomes less dense (lower pressure) and a compresser is needed anyway. The two speed supercharger ( not turbocharger ) first apeared in WW2. So starting and flying at altitude would be easy.
With these thoughts in mind you could net an engine with the following specs:
200 hp at 2800 RPM Normalized to 20,000 feet.
Engine weight that is very comparable to an IO360.
Engine life around 4000 hours.
An electric preheater would make the engine usable in any climate.
This sounds like a dream but very easy and do able.
Lee


Sounds a lot like what DeltaHawk is trying to put together.

PJ

leeschaumberg
04-30-2005, 08:41 AM
Delta Hawk Engine is trying to make a non smoth engine smooth and reinventing the wheel. For enough money , some people will say or do any thing.
Lee

mlw450802
04-30-2005, 09:23 PM
... HP=TxRPM/3300,.../I hate to nit pick but since none of the other arguments will truly sway anyone away from his opinions, I thought I would just correct this formula.
One horsepower is a work rate of 33,000 ft-lb/minute.
If we have a torque of one ft-lb and we calculate the work done by that in one revolution of the crankshaft, then we will have done 2pi ft-lbs of work.
In order to determine how many rpm we need to get one horsepower out of that, we need to divide 33,000 by 2pi.
This gives us ~5252rpm.

The formula should be HP=t*RPM/5252. The neat consequence of this formula is that torque and horsepower are always numerically identical at 5252rpm.

Sorry again and no offense intended.
-Mike

ship
05-01-2005, 01:30 AM
just for kicks, let's flip this discussion on it's ear.

the NEWEST production (notice i said "production") engine type -- of any kind -- is over 60 years old. for those that are counting, that would be the axial compression internal combustion engine, a.k.a. the gas turbine.

we're talking about "core engine design" ... not peripherals like FADEC, etc.

the piston engine hasn't changed in over 100 years. improved, yes. but the fundamental design is exactly the same.

ask yourself why there are no turbine cars cruising the highways. simple, light, long-life, etc. what happend? turbine concept cars were all the rage in the 50's....certainly the advances in technology should be able to make a turbine car an affordable reality today.

why not? because it doesn't fit the mission. in stop & go traffic, a bicycle can out-accelerate a turbine car up to 10mph. (we're not talking about jet trucks at airshows). you'd also be riding the brakes up to 60mph since turbines idle at 80% power. not to mention getting about 2mpg and an exhaust the size of a sewer pipe.

i am all for experimental installations, but let's face it -- 99.99% of builders are not experimenters. An RV is the FARTHEST thing from an experimental plane you can get...and the success of Van's is a direct result of his "no experimental" philosophy

..the main issue here is suitability, safety and longevity.

if you're reading this thread b/c you want to learn about engines in airplanes, there are several posts in this thread which make very clear, concise arguments for the following wisdom:

form follows function.

car engines are for cars, truck engines are for trucks, boat engines are for boats......and airplane engines are for airplanes.

sounds obvious, but the reality is quite compelling. the dominant airplane engine design for light aircraft has EVOLVED into what works best.

there is NOTHING that hasn't been tried in airplanes over the past 75 years. turbines, diesels, car engines, steam, rotary....even nuke....you name it

the first diesel aircraft engine flew in 1930!! the DeltaHawk may be "new" but at least it was designed PURELY as an airplane engine

sometimes a design reaches a perfect point.....the B52 bomber is a perfect example of something that got it right....sure it has new engines and avionics, but it will still be flying at 100 years old.

we still can't fly like birds, but when was the last time you saw a 400 ton pelican doing 600mph at 35000 feet?

the concorde was a wonderful airplane but an utter failure as an airLINER....it simply did not fit the mission

an F18 is a great plane....but not exactly a "day-VFR go get a burger" kind of ride

canards are "more perfect" airframes....yet they are not nearly as user-friendly or as flexible as conventional planes.

the bottom line is that engines designed for other purposes are AT BEST a serious compromise in an airplane installation.

not because the "technology" is better or worse, but because the design is entirely unsuited to the mission it is being asked to perform.

the subaru engine has been fairly successful because it happens to be relatively close to an aircraft-type design. durability and reliability in airplane mission are the unknowns. the eggenfellner installation has many good points....it remains for accumulation of fleet hours to work out the inevitable kinks and weaknesses in a complex installation.

if you took a clean sheet of paper and designed an engine for an airplane, you'd end up with an airplane engine...not a car engine. it might be a diesel or a turbine or a gasoline engine...but it would be an airplane engine for airplane missions.

if you choose to pursue a conversion engine installation, be very realistic about sacrificing one or more of the qualities you are looking for in an airplane engine (longevity, reliability, cost, weight, simplicity, efficiency, ease of maintenance, field support, durability, etc.).

leeschaumberg
05-01-2005, 11:23 AM
Sorry to correct you but a turbine engine is an external combustion engine. An internal combustion engine uses pistons. Please see any book on engines to confirm this fact.
Lee

Tandem46
05-01-2005, 12:03 PM
Sorry to correct you Lee, but a gas turbine as it applies to aviation is an internal combustion engine. A steam engine is an external combustion engine. There are external combustion turbines, but they'd be driven by steam.

Reference this:

"The Basics
The purpose of a gasoline car engine is to convert gasoline into motion so that your car can move. Currently the easiest way to create motion from gasoline is to burn the gasoline inside an engine. Therefore, a car engine is an internal combustion engine -- combustion takes place internally. Two things to note:

There are different kinds of internal combustion engines. Diesel engines are one form and gas turbine engines are another. See also the articles on Hemi engines, rotary engines and two-stroke engines. Each has its own advantages and disadvantages.

There is such a thing as an external combustion engine. A steam engine in old-fashioned trains and steam boats is the best example of an external combustion engine. The fuel (coal, wood, oil, whatever) in a steam engine burns outside the engine to create steam, and the steam creates motion inside the engine. Internal combustion is a lot more efficient (takes less fuel per mile) than external combustion, plus an internal combustion engine is a lot smaller than an equivalent external combustion engine. This explains why we don't see any cars from Ford and GM using steam engines."

Quoted off of Howstuffworks.com

Tobin

mlw450802
05-01-2005, 12:19 PM
Sorry to correct you but a turbine engine is an external combustion engine. An internal combustion engine uses pistons. Please see any book on engines to confirm this fact.
LeeActually, Mr. Shaumberg, the Brayton cycle engine as used in aircraft operations IS an internal combustion engine, operating in an open cycle. There is no restriction on internal combustion engines that they be constructed using pistons.
Gas turbines operated in a CLOSED cycle where the working fluid is continuously recirculated is not an I.C.E. because the fluid cannot support continuous combustion and the heat energy needs to be added externally to the cycle.

-Mike

szicree
05-01-2005, 02:02 PM
I don't see what all the fuss is about. What is so wrong with Lycomings other than the ridiculously high cost (which is mostly a consequence of simple supply/demand issues)? These things run great and last and last. They can be brought into the modern age by simply using a more modern ignition or FADEC. I just don't see what is so bad about them.

PJSeipel
05-01-2005, 02:56 PM
I don't see what all the fuss is about. What is so wrong with Lycomings other than the ridiculously high cost (which is mostly a consequence of simple supply/demand issues)? These things run great and last and last. They can be brought into the modern age by simply using a more modern ignition or FADEC. I just don't see what is so bad about them.

Biggest changes I'd like to see would be liquid cooling (no worry about shock cooling, reduces need for complex engine management) and less reliance on 100LL (I'm partial to diesel/Jet-A, but anything's better than 100LL).

PJ

szicree
05-01-2005, 04:01 PM
As for water cooling, it adds weight and complexity, and lots of new failure points. Think of how many times you've seen cars on the side of the road steaming. As for the fuel, use lower compression pistons and you can run mogas. It just seems that the old Lycoming can be adapted to do just fine with a whole lot less work than trying to adapt an auto engine to an airplane.

PJSeipel
05-01-2005, 05:14 PM
As for water cooling, it adds weight and complexity, and lots of new failure points. Think of how many times you've seen cars on the side of the road steaming. As for the fuel, use lower compression pistons and you can run mogas. It just seems that the old Lycoming can be adapted to do just fine with a whole lot less work than trying to adapt an auto engine to an airplane.

Not all that often. Assuming the vehicle is maintained it shouldn't be an issue, although I agree that there are trade-offs.

I'll turn it around on you and ask you how many people you know who've had to replace cylinders on their car? Now ask that same question of pilots you know.

PJ

leeschaumberg
05-01-2005, 06:46 PM
Actually, Mr. Shaumberg, the Brayton cycle engine as used in aircraft operations IS an internal combustion engine, operating in an open cycle. There is no restriction on internal combustion engines that they be constructed using pistons.
Gas turbines operated in a CLOSED cycle where the working fluid is continuously recirculated is not an I.C.E. because the fluid cannot support continuous combustion and the heat energy needs to be added externally to the cycle.

-Mike
All of the companies that I worked for (5 companies) said the turbine was an external combustion engine. The Milwaukee School of Engineering said a turbine is an external combustion engine. You say it's not! Hmmmmm I wonder who I should believe?
Lee

leeschaumberg
05-01-2005, 07:03 PM
As for water cooling, it adds weight and complexity, and lots of new failure points. Think of how many times you've seen cars on the side of the road steaming. As for the fuel, use lower compression pistons and you can run mogas. It just seems that the old Lycoming can be adapted to do just fine with a whole lot less work than trying to adapt an auto engine to an airplane.
Would you please forget automobile engines.
Water cooled engines are a big IMPROVMENT over air cooled engines. Many people still think air cooling is cool. The Wright Bros. if still alive wouldn't think so. Lycoming and other aircraft engine manufacturers have water cooled engines in thier test labs. They will introduce them when they want to. You compare water cooled engines to a jerk (Not You) driving a car that doesn't believe in proper maintainence. Lawn mowers still use air cooled engines because thier cheaper to manufacture. I know , I worked for Briggs and Stratton.
Lee

szicree
05-01-2005, 07:34 PM
On cars I've owned I've had: brand new water pump fail, brand new thermostat fail, brand new temp sending unit fail, debris rupture radiator core. I'm sure there have been others. I know water cooled is the way to go for cars, but perhaps not for all things. Motorcycles, for example, often run air cooled engines. I have one of each type, and can tell you that the water cooled engine is much heavier. I guess I'm just from the "if it ain't broke, don't fix it" school, and I can't see what's so broke about our current motors.

On the debate about internal vs. external, all resources I've checked define an internal combustion engine as any engine in which the expansion of combustion gasses DIRECTLY drive the engine. This would, of course, include both piston and turbine types, and exclude the good old steam engine.

Incidently, I have some trouble believing that the Milwaukee School of Engineering speaks as a single entity on any subject.

Tandem46
05-01-2005, 08:40 PM
Not sure why I'm argueing this silly point still, but Lee, how about this one:

Dictionary

(Click to enlarge)
gas turbine
turbojet engine
(Precision Graphics)
gas turbine
n.
An internal-combustion engine consisting essentially of an air compressor, combustion chamber, and turbine wheel that is turned by the expanding products of combustion.

Like Szicree, every website I checked out supports this. Besides, where'd you get the idea that IC must have pistons? Internal means internal. The pistons only compress air, just like the compressor blades in the gas turbine.

On another note Lee, I agree with you 100% on your liquid cooling post. Properly maintained, the liquid cooling system is no more prone to breakdown than our current setup on Lycs for the oilr cooler/pumps/hoses.

Tobin
(In an arguementative mood, Sunday night and bored I guess, though I did log a 1.2hr this afternoon in my -7:) )

mlw450802
05-02-2005, 07:30 AM
All of the companies that I worked for (5 companies) said the turbine was an external combustion engine. The Milwaukee School of Engineering said a turbine is an external combustion engine. You say it's not! Hmmmmm I wonder who I should believe?
LeeBelieve whomever you want but it is still a fact that SOME turbines are internal combustion engines and SOME are external combustion engines. The determining factor is whether the heat added to the working fluid is added internal to the cycle or external to the cycle. It is as simple as that.
In all jet aircraft and turboprops, the combustion cannister is inside the engine, using the air flowing through it as the working fluid.
It is entirely likely that all the companies you worked for were building turbines that were externally heated for their operation in which case they would have been correct about "their" turbines being external combustion engines. It is one of those life experiences that unfortunately enforces a myopic view of the world. It has happened to most of us at one time or another.

Broadening the discussion slightly, a piston engine is not necessarily an I.C.E. either. Sterling cycle engines are routinely constructed using pistons in their design but the working fluid is in a closed cycle and the heat must be added externally. Another example that we are all familiar with is the old fashioned steam driven locomotive. It is an externally heated combustion engine.
Changing the fuel to a combustible gas and adding a spark ignition such that the combustion takes place in the cylinder could convert the same engine to an internal combustion engine.

The only difference is where the combustion takes place and a necessary and sufficient part of an I.C.E. is that the WORKING FLUID take part in the combustion process. That's where the 'Internal' adjective comes from. It describes whether the combustion, in the heat engine being described, occurs internally within the working fluid or externally to it.

Again, believe whomever you want but quoting words from the Cold War, "trust but verify"

-Mike

mlw450802
05-02-2005, 10:11 AM
Encyclopaedia Brittannica Article.

Internal combustion Engines

"...any engine in which a fuel-air mixture is burned in the engine proper so that the hot gaseous products of combustion act directly on the surface of its moving parts, such as that of a piston or turbine rotor blade. Internal-combustion engines are the most widely used of all present-day power-generating systems. They include gasoline engines, diesel engines, gas-turbine?

-Mike

leeschaumberg
05-02-2005, 08:16 PM
To all readers , Mike , and Tobin

I wish to apologize to all the readers of this thread.
I have been incorrectly made to believe that all turbines were external combustion engines. In reality all turbines that are driven by an external process like the formation of steam are external combustion engines. Aircraft turbines generate heat from the burning of a fuel within thier structure. A fuel is injected into the combustion chamber and stays burning until a (flame out) occurs. This hot air expanding turns the turbine wheel or wheels.
Over the years a school and many manufacting companies have helped me to believe that all turbines are external combustion engines. I now know why. Everybody from my part of the country (southeast wisconsin) only builds piston engines! Back when I thought it was dumb. I was right.
I do not have a PHD in engineering so I didn't know. Word to the wise ( assume nothing ).
Again I apologize
Lee

rvwant2b
05-02-2005, 08:28 PM
I like the discussion but I think you guys are getting to hung up on words. "internal vs External"

Both pistions and turbines do the same thing.

suck, squeeze, bang, and blow.

:)

mlw450802
05-02-2005, 09:25 PM
To all readers , Mike , and Tobin

I wish to apologize to all the readers of this thread.
I have been incorrectly made to believe that all turbines were external combustion engines. In reality all turbines that are driven by an external process like the formation of steam are external combustion engines. Aircraft turbines generate heat from the burning of a fuel within thier structure. A fuel is injected into the combustion chamber and stays burning until a (flame out) occurs. This hot air expanding turns the turbine wheel or wheels.
Over the years a school and many manufacting companies have helped me to believe that all turbines are external combustion engines. I now know why. Everybody from my part of the country (southeast wisconsin) only builds piston engines! Back when I thought it was dumb. I was right.
I do not have a PHD in engineering so I didn't know. Word to the wise ( assume nothing ).
Again I apologize
LeeJeez Lee!
No apology necessary! As I said in one of my posts, I have incorrectly and even sometimes stubbornly held to an opinion only to find later that my experiences were not as all-encompassing as I had believed. You are a bigger person that I may have been here if the tables were turned. This just happened to be an area where my education was specialized and the definitions were easily recalled to me. I am sure there will be many opportunities for you to educate me with your experiences and I just hope I am smart enough to realize it when it happens.
-Mike

szicree
05-03-2005, 12:51 AM
Jeez Lee!
No apology necessary! As I said in one of my posts, I have incorrectly and even sometimes stubbornly held to an opinion only to find later that my experiences were not as all-encompassing as I had believed. You are a bigger person that I may have been here if the tables were turned. This just happened to be an area where my education was specialized and the definitions were easily recalled to me. I am sure there will be many opportunities for you to educate me with your experiences and I just hope I am smart enough to realize it when it happens.
-Mike

Ditto

Steve Zicree

leeschaumberg
05-03-2005, 05:13 AM
To all that wrote
Thank You all. I might be dumb but not stupid! I do have much dyno experiance using natural gas(almost 120 octane) , propane (low in octane) and hydrogen (almost 120 octane). Now that we have carbon fibre for storage I think the later is the winner. Now all I need is a flyable RV8 not a RV8A.
Lee

ship
05-04-2005, 02:31 AM
wow! i'm gone for a day and look what happens. :D

(lee: don't feel bad....we all make mistakes. i know i've made more than my fair share of doozies in various emails over the years.)

i've been fortunate to be closer than most folks to the birth of an aircraft engine from clean-sheet design. lots of dyno time and burnt engines. the only sure thing is that all bets are off when you move from the dyno to the test rig. even the dyno is a big unknown the first time around.

people like to bash lycosaurs, but this is a bum rap. the statisitcal reality is the lyco 320/360 and the TCM 470 are the most reliable piston engines ever built. ever. that includes the millions of small-block chevy/ford engines, truck diesels, etc.

is there room for a new engine design in GA? absolutely.

you don't have to look very far to see that a good "design" doesn't guarantee success....the bigger Lyco and TCM engines are far less reliable even though they are DIRECT derivatives of the smaller engines.

being fairly privvy to what's happening in the aircraft engine world, i can say with relatively high confidence the following:
-- engine design is extremely complex & expensive....if it was easy & cheap everyone would do it.
-- trivia: GM and Ford are spending $1billion to jointly develop a SINGLE new transmission for light trucks...that's how bad it is
-- $20k for an engine is a BARgain .... a 20hp lawn-mower diesel costs $5k
-- there's far less profit than you think in a Superior or ECI engine.
-- shock-cooling issues are 99% pilot error
-- slow revving engines last longer than fast revving engines
-- the flat aircooled design is closest thing you'll find to the perfect piston engine for light aviation
-- the Lyco 320/360 and TCM 470 are statisitcally the most reliable piston engines ever produced
-- lycomings, radials, etc. ARE liquid cooled...it's called fuel...no need for heavy radiators, etc.
-- the Lyco/TCM conspiracy to keep new technology on the shelf is bogus...the cost of development to get through FAA certification is horrendous with no guarantee of success....they own the market already
-- the TCM gap project is a crime....that money should've gone to one of the startups like DeltaHawk
-- automotive designs will never succeed as aircraft engines...e.g. the Bombardier engine is far too complex even though it was designed as a pure aircraft engine.....Orenda tried it....lost $40million
-- subie conversions will do better than rotaries over the long haul
-- only 1 diesel has potential to succeed commercially...DeltaHawk
-- no turbine will succeed commercially below 350hp due to BSFC
-- survey of importance in ACTUAL engine purchase decisions: reliability, economy, price, latest technology

FUN FACTS
form follows function: top fuel dragster
type V8
horespower 8000hp@6000rpm...1,000hp PER cylinder!!
torque 7000ftlb@6000rpm
weight 550lbs
fuel flow 180gpm...that's 10,800gph...or 1000x lycoming
cost $75,000
TBO 10 seconds (2 runs)

RudiGreyling
05-04-2005, 06:44 AM
Nice debate,

Nice write up/summary from Ship,

Question for "Ship":
i've been fortunate to be closer than most folks to the birth of an aircraft engine from clean-sheet design. Ship, could you shed more light on your statement?

rv6ejguy
05-04-2005, 04:55 PM
Oh boy, where do I start.

Automobile engines may be of a higher technical level than a Lycoming, but they are NOT superior when it comes to driving an airplane through the sky. Take a look at the main crank bearings and the engine block of a Subaru and compare them to the Lyc. When you are swinging the weight of the prop out front, it requires some hefty support. Lyc's also deliver peak power at low RPM, while the Subies need to scream along at much high RPM to deliver peak horsepower, hence the gear reduction units. I contend that automobile engines are very poor airplane engines because they need to be jerryrigged to make them work.

I fly a Sube and rebuilt the engine myself being a racecar engine builder by profession. The engineering, metallurgy, choice of materials, machining and balance of the Sube is far superior to anything seen in a Lyc. I have never heard of a bottom end failure on the EJ series Subes. There is no doubt that they can take much higher continuous stress. This was proven by their wide open run : http://www.subaru-global.com/about/history/1989-001.html#subhead-001

Anyone who thinks that modern auto engines are not capable of spinning at 4500 rpm all day, all month, all year long is simply ill-informed. I built and road raced Japanese engined cars for 13 years making over 5 times their naturally aspirated stock power and running them 2500 rpm over the stock redline. Not one ever suffered a catastophic failure.

The benefit they have is that they are cheap because they are mass produced. Can't beat that. They also have great reliability when used for their intended and designed use. Start sticking them in airplanes and you are bringing along a whole additional set of engineering problems to be solved. I don't know any engine engineer that thinks gear reduction units are the best way to turn a prop. No, it's just a band-aide stuck on an engineering problem that otherwise, can't be fixed.

What is this? Every Pratt, Wright, Allison, and Merlin had a reduction gear. You call that a band-aid?

The whole 100LL thing has become the enabling battle cry of the alternate engine groupies. Unfortunately, it doesn't hold water. No one is going to wake up one moring to find that hundreds of thousands of engines that use the product suddenly are silent because no one is making it any longer. I don't doubt that there will be a transition to other fuels in the long run. That's probably why the diesel engine is looking like a viable engine alternative. But you and I will be able to buy 100LL for many, many years to come. Now the price of that gallon of 100LL may be another issue.

My Sube runs on 100LL just fine or 91 octane if I choose.

Finally, the reason I fly a homebuilt and not a Cessna 150 is because I can upgrade my Lycosaur with electronic ignition, FADEC, etc and get the best of both worlds----newer features and capabilities with proven reliability.

Proven? Every 24 hours, there are more high speed hours put on cars running in Germany alone, than all the Lycoming engines ever built have accumulated in the last decade. For every hour that Lycs have, cars have accumulated millions of hours. You don't think Lycs break? Better brush up on those accident reports. There are plenty of fatals caused by catastrophic failures and don't forget the class action suits brought against Lyc and their turbocharged 540s where dozens blew up or went only a fraction of the time to TBO. Let's not forget the recent judgement against Lyc for the crank problems and all the other problems these "proven designs" have suffered in the last 5-6 years. This is a joke when you are paying $30,00+.

Some might find this interesting: http://www.sdsefi.com/air7.html

rv6ejguy
05-04-2005, 05:00 PM
Oh boy, where do I start.

Automobile engines may be of a higher technical level than a Lycoming, but they are NOT superior when it comes to driving an airplane through the sky. Take a look at the main crank bearings and the engine block of a Subaru and compare them to the Lyc. When you are swinging the weight of the prop out front, it requires some hefty support. Lyc's also deliver peak power at low RPM, while the Subies need to scream along at much high RPM to deliver peak horsepower, hence the gear reduction units. I contend that automobile engines are very poor airplane engines because they need to be jerryrigged to make them work.



The benefit they have is that they are cheap because they are mass produced. Can't beat that. They also have great reliability when used for their intended and designed use. Start sticking them in airplanes and you are bringing along a whole additional set of engineering problems to be solved. I don't know any engine engineer that thinks gear reduction units are the best way to turn a prop. No, it's just a band-aide stuck on an engineering problem that otherwise, can't be fixed.



The whole 100LL thing has become the enabling battle cry of the alternate engine groupies. Unfortunately, it doesn't hold water. No one is going to wake up one moring to find that hundreds of thousands of engines that use the product suddenly are silent because no one is making it any longer. I don't doubt that there will be a transition to other fuels in the long run. That's probably why the diesel engine is looking like a viable engine alternative. But you and I will be able to buy 100LL for many, many years to come. Now the price of that gallon of 100LL may be another issue.



Finally, the reason I fly a homebuilt and not a Cessna 150 is because I can upgrade my Lycosaur with electronic ignition, FADEC, etc and get the best of both worlds----newer features and capabilities with proven reliability.

Oops, screwed up the quote in the last post there:

I fly a Sube and rebuilt the engine myself being a racecar engine builder by profession. The engineering, metallurgy, choice of materials, machining and balance of the Sube is far superior to anything seen in a Lyc. I have never heard of a bottom end failure on the EJ series Subes. There is no doubt that they can take much higher continuous stress. This was proven by their wide open run : http://www.subaru-global.com/about/history/1989-001.html#subhead-001

Anyone who thinks that modern auto engines are not capable of spinning at 4500 rpm all day, all month, all year long is simply ill-informed. I built and road raced Japanese engined cars for 13 years making over 5 times their naturally aspirated stock power and running them 2500 rpm over the stock redline. Not one ever suffered a catastophic failure.

What is this? Every Pratt, Wright, Allison, and Merlin had a reduction gear. You call that a band-aid?

My Sube runs on 100LL just fine or 91 octane if I choose.

Proven? Every 24 hours, there are more high speed hours put on cars running in Germany alone, than all the Lycoming engines ever built have accumulated in the last decade. For every hour that Lycs have, cars have accumulated millions of hours. You don't think Lycs break? Better brush up on those accident reports. There are plenty of fatals caused by catastrophic failures and don't forget the class action suits brought against Lyc and their turbocharged 540s where dozens blew up or went only a fraction of the time to TBO. Let's not forget the recent judgement against Lyc for the crank problems and all the other problems these "proven designs" have suffered in the last 5-6 years. This is a joke when you are paying $30,00+.

Some might find this interesting: http://www.sdsefi.com/air7.html

Jconard
05-04-2005, 06:05 PM
Having road raced in open wheel cars for 13 years....

1. An airplane engine only has to be efficient within a very narrow RPM band 2-2.5K rpm, which makes most of the advanced control systems on a car unnecessary.

2. A racing engine also has to respond smoothly and instantly to throttle changes, which an airplane engine really does not have to...I know what people are thinking..."going around", but that is not the kind of response needed from a race engine coming out of a corner..modulation is the ey to the race engine. The net is that there too are all sorts of demands and systems not needed.

3. The racing engine does not experience anywhere near the torsional stress impsed on an airplane from the 7-foot diameter 60lb flywheel, which is the prop.

4. Within the application of a 500 rpm operation spread, almost constant speed operation, mechanical fuel injection and fixed timing are elegant and do not loose much.

5. The cranks in a sube are tiny, perfect for changing rpm all the time, but no dampening mass for constant running.

6. Liquid cooling is unnecesary, adds weight, and complexity. Aircooling works great when it is freezing, it works great when it is hot, it is simply and light.

Recently an H-6 RV-7 subaru pilot posted speeds and fuel burns from his plane. They were amazingly slow and high, given all the claims.

For example: at 8500 ft

RPM 2200/3970
BURN = 8.6
TAS = 141 (162)
MPG = 18.83

This is about ten knots slower and the same fuel burn as a 160hp lycoming rv7a I know got with no wheel or leg fairings. It will be about 100lbs heavier, and have no provision for a hydrolic prop.

With all the superiority, it makes you wonder where the performance is...

f1rocket
05-04-2005, 07:45 PM
There is no doubt that they can take much higher continuous stress. This was proven by their wide open run : http://www.subaru-global.com/about/history/1989-001.html#subhead-001
I'm sorry, but there is plenty of doubt. There is absolutely no track record of this engine performing in an aviation environment. Talk to me in ten years.

Anyone who thinks that modern auto engines are not capable of spinning at 4500 rpm all day, all month, all year long is simply ill-informed. I built and road raced Japanese engined cars for 13 years making over 5 times their naturally aspirated stock power and running them 2500 rpm over the stock redline. Not one ever suffered a catastophic failure.
Was it swinging a 70 lb prop at varying density altitudes and temperatures? If not, then the facts are irrelevant when it comes to using them as aviation engines. Anyone who thinks just because an automobile engine can rev at 4500 RPM on a test stand for months at a time, this makes it suitable for use in an airplane is not only ill-informed, but seriously under-estimating the engineering difficulties of adapting automobile engines for aviation usage. If it was easy, everyone would have already done it.

What is this? Every Pratt, Wright, Allison, and Merlin had a reduction gear. You call that a band-aid?
For the most part, yes. This was the fastest way to adapt these engines to their relative airframes during the war, where getting the thing into the theater of war was more important than elegant engineering solutions. I know of no engineer that thinks adding more moving parts, more complexity, more friction, is a better solution than a direct-drive engine. It does have it's application in very specific engineering solutions, but for the most part, it is to be avoided if possible.

Proven? Every 24 hours, there are more high speed hours put on cars running in Germany alone, than all the Lycoming engines ever built have accumulated in the last decade. For every hour that Lycs have, cars have accumulated millions of hours. You don't think Lycs break? Better brush up on those accident reports. There are plenty of fatals caused by catastrophic failures and don't forget the class action suits brought against Lyc and their turbocharged 540s where dozens blew up or went only a fraction of the time to TBO. Let's not forget the recent judgement against Lyc for the crank problems and all the other problems these "proven designs" have suffered in the last 5-6 years. This is a joke when you are paying $30,00+.
Again, automobile engines running in automobiles is irrelevant to the engineering problems in aviation. There are a handful of Subies flying and more than a couple have already suffered failures of one kind or another. The Lycoming problems you cite are a result of component manufacturing problems, not with the design. The only reason you know about the problems is that the FAA requires stringent reporting requirements so that the history and track record can be examined and reviewed. Where is that documentation on the Subie? It doesn't exist. You don't know of the failures. You don't have any idea if the engineering can hold up in an airplane because there haven't been enough hours flown on them to produce a track record to examine. If the Subie lasts as long as the Lycoming, and it's reliability is even close to the Lycoming, then they will have accomplished something.

BTW, the cost of the Lycoming has more to do with product liability than manufacturing. All it will take is one Subie user (or their family) to sue them and win, and they will be out of business but fast.

rv6ejguy
05-05-2005, 11:10 AM
You guys need to get you heads out of the sand. Rotary Airforce has sold over 400 Gyros powered by Sube EJ22 engines over the last ten years. High time one has 2500 hours on it. Fleet has close to 100,000 hours on them. I can't find a single internal mechanical failure in any accident report involving this airframe/ engine combo.

The WW2 aero engines had reduction gears on them to enable higher outputs and more efficient propeller operation. You think you know more than the engineering teams that designed these engines? Using an auto engine which is most efficient turning around 4500 rpm in cruise requires a redrive for the same reasons. This is sound engineering. The redrive also isolate torsionals from the crank and supports prop loads. The good redrives offered by Powersport, Marcotte, NSI and now the damped Eggenfellner solutions have some good to excellent engineering, testing and flight time on them. They are proven and reliable. Certainly some of the redrives offered in the past and even today were/are poor but refinement has got some good ones out there now.

Yes, present state of the art means that the average Sube will be heavier than a Lyc. The E-Subes have higher fuel burn due to their stock ECUs being in open loop at high power settings. With programmable EMSs, we find fuel burn very similar to a Lyc at the same TAS because we can properly map to a more effient AFR. Some new NSI Subes are flying now and we hope these and some Egg owners will be going to Van's this year to test head to head against the Lycs.

Cars on the autobahn are routinely cruised at 4500 rpm + for their whole lives. They are not littering the sides of the road with broken engines.

The crank is smaller on the Sube because it is only a 134 cubic inch engine. All the components are smaller because the must be. This does not mean that they are weaker. Pistons speeds for a Sube at 4500 are similar to a long stroke Lyc at 2400 rpm, therefore inertia loads are similar. They are in no way at any dangerous levels. My Sube knows no difference that it is attached to a redrive spinning a prop than it would being driven on the road at 110 mph.

szicree
05-05-2005, 11:36 AM
If the Sube is heavier and burns more fuel, why is it better that a Lyc?

f1rocket
05-05-2005, 11:50 AM
If the Sube is heavier and burns more fuel, why is it better that a Lyc?
Bingo. And I'm the one with my head in the sand! :cool:

I'm glad you like your Subie, and I hope it lasts a long time and that you are safe. Although it's not for me, I'm glad it fits for you.

The intent of the thread was not to cast aspersions upon the alternative engine crowd, but rather to give newbies some food for thought when considering engine alternatives. If one were to just consider all the hype out there, an unsuspecting new builder might think that the Subie is a proven, tested, cheaper, more efficient, lighter, easier to operate, easier to install, and effective alternative to Lycoming. While we disagree on whether it is or isn't, folks need to look at all these aspects before deciding which engine is right for them.

Scott DellAngelo
05-05-2005, 12:00 PM
Cars on the autobahn are routinely cruised at 4500 rpm + for their whole lives. They are not littering the sides of the road with broken engines.


True, but how much horsepower is that engine producing to cruise a car down the road at 4500? I'm betting a bunch less than when pulling the airplane along at 4500 in cruise.

Scott

djvdb63
05-05-2005, 12:20 PM
Recently an H-6 RV-7 subaru pilot posted speeds and fuel burns from his plane. They were amazingly slow and high, given all the claims.

For example: at 8500 ft

RPM 2200/3970
BURN = 8.6
TAS = 141 (162)
MPG = 18.83

This is about ten knots slower and the same fuel burn as a 160hp lycoming rv7a I know got with no wheel or leg fairings. It will be about 100lbs heavier, and have no provision for a hydrolic prop.

With all the superiority, it makes you wonder where the performance is...

In fairness, it should be noted that that same pilot, posting two days ago on the Egg list, says he is now getting about 10 knots more than last August (when those numbers you quoted were first posted), after adding upper and lower intersection fairings. He also indicates there is considerably more that can be done regarding drag reduction vis-a-vis the cowl installation of Egg's H-6 engine.

Let me make a few random Egg-Sub observations...not as a customer, but as an observer and potential customer:

My take, as a long-time observer, on the Egg-Sub situation is that, with the H-6, they have finally achieved performance roughly equal to a 160 hp O-320 or IO-320, but at a considerable weight penalty (the two H-6 RV-7A's that have produced the most data thus far are both coming in with empty weights of about 1280 lbs...both fairly well equipped). This is disregarding the issues of initial engine cost & initial prop cost. It is also disregarding issues of resale value, durability, overhaul cost, etc....much of which remains unknown.

One can only speculate as to why the H-6 doesn't produce performance more in keeping with it's claimed 190 hp. Other than it's weight, I would suspect cooling drag as the culprit...which has been extensively debated on the Egg Yahoo list. And the required 3-blade prop might cost 2 or 3 kt., and the PSRU might cost some power as well. Mr. Egg consistently refuses to produced dyno data to support his HP claims, but I would guess that a dyno would likely confirm his HP estimates since he is not altering the basic engine in any substantial way from it's automobile configuration.

The supercharged 2.5L STi Egg engine is a different story. Production is currently "on hold" while initial installation and teething difficuties are sorted out. My guess is that this engine, once optimized, will produce performance somewhere between an 180 hp and 200 hp Lycoming with somewhat less of a weight penalty. The complexity of this engine installation, with resultant higher maintenance and pilot work-load issues...as well as durability issues, will lilkely be the trade-off here.

My biggest concern about Egg's engine packages remains the high-flow fuel system with both fuel pumps on the floor of the cockpit. Just a visceral safety concern that I have in the event of a mishap. Apparently the high flow is necessitated by the FI system on the Sub. A more desirable solution....low flow system from wings to header tank...high flow from header tank to engine...is apparently not possible on RV's but has been used on Glastars.

Another concern is that Egg has become much less transparent in the past couple of years. His list is now heavily edited, and almost nothing negative is allowed to get through. This makes it harder to really assess the degree of customer satisfaction and feedback. But I somewhat understand his defensiveness, having watched him get ripped and flamed mercilously from various quarters in the past.

Remember the percieved benefits: MUCH lower vibration than a 4-cyl Lycoming. Effective cabin heat for us northerners. Lower pilot workload...like a car. Just start it up and go....full throttle from takeoff until descent...using the prop controller to regulate power. No mixture to worry about. No carb heat. Very simple initial installation. Projected lower ongoing maintenance workload and costs.

Overall I think Jan deserves credit as there are arond 100 of his engines flying. Nobody has gotten ripped off. Most of his customers are happy (I think...as this is getting harder to assess). His movement is growing...and his product is improving.

Of course, time will tell, as it always does.

Dan

rv8ch
05-05-2005, 01:30 PM
The debate about traditional aviation engines vs. the auto conversions reminds me of the command line interface vs. graphical user interface debates of the middle 80s when I worked for IBM. I did a blasphemous thing and bought an Apple Macintosh in 1984, which of course had a GUI. While I still enjoy using a CLI on my linux machines, most of my work is with the GUI.

Still being a blasphemous kind of guy 20 years later, I bought an Eggenfellner Subaru 2.5XT with a supercharger. I enjoy flying behind any kind of engine, but I only have aircraft available to me with traditional aviation engines, which is why I chose the subaru for this project. If I like it, I'll keep it. If not, I'll yank it out and install something else. Hopefully before the end of the year I'll be flying, and I'll be happy to report any details.

rv6ejguy
05-05-2005, 01:33 PM
True, but how much horsepower is that engine producing to cruise a car down the road at 4500? I'm betting a bunch less than when pulling the airplane along at 4500 in cruise.

Scott

If we take average hp to take a modern car down the road at 70mph being around 20 hp, to cruise at 140 mph on the autobahn would take around 160 hp. Certainly in the ballpark of a Lyc O-360 at 75%. My BMW turns about 3000 rpm at 75 mph in top gear so 5600 to do 140 mph. This happens every day in Europe. Even the 1300-1600cc cars are cruised at 100+mph for hours on end, foot to the floor WOT 6000+ rpm, just like hundreds of showroom stock endurance racing cars.

I'm just wondering what evidence you fellows have to prove that auto engines are having internal mechanical failures in aircraft because they can't take it? Please show us.

DJVDB63 sums things up very well here with the Egg conversions from a neutral standpoint. The supercharged or turbocharged 4 cylinder Subes and Wankels would appear to offer close to equal weight and performance to the Lyc with all the advantages he listes here. Hundreds of people are buying and flying these conversions. It's unlikely that none of them considered a Lycoming and ended up spending $20,000+ on a Sube or Wankel instead by mistake. Most users to date seem quite pleased with their choices and few problems have been reported. These engines have accumulated several thousand flight hours to date. Choosing a Sube or Wankel is not a death wish, it's just another choice we have now instead of a Lyc. Eggenfellner and others are advancing the installation and performance of the Sube and deserve much credit. I develop my turboed Sube to make it better. Others such as Tracy Crook and PowerSport with the Wankels have forged the way for others to follow with those engines.

Jconard
05-05-2005, 02:17 PM
Since the begining of aviation people have tried to convert auto engines. So far the only successful ones have been the air cooled VW, and the old jennies.

The performance per weight is not equal...look at the numbers.

The advantages are mostly percieved. People believe that electronic injection, etc are superior. For an engine with a wide rage of rpm operation, and a need for smooth but instant throttle response that modern injection does have advantages. Neither are necessary in an aircraft. The magneto, and constant rate fuel injection or carb are simple, elegant, and bulletproof.

The hundreds of flying examples argument is simply laughable. There are more lycoming hours flown today, than all the subaru hours combined.

As for ability to withstand the forces, I have rebuilt both types of engines, and have seen the bearing and crank setups. The auto is a great design for rapid reving, crisp throttle response, and an engine which will spend most of its life far below maximum output.

The aircraft crank is beefy to handle resonance and gyroscopic loads from the prop. Remembber that a prop is a 60 lb pair of flywheel arms that are constantly accelerating and decelerating. This adds torsional stress and harmonics that an auto crank is not able to handle. This is why the VW conversions, even with chromoly scat cranks, (far stronger than a sube crank, often used in alcohol midgets), still can only use a lightweight wooden prop.

Air cooling is also superior. The goal is to transfer heat with minimal air, hence minimal drag. Each instance of heat transfer is less than 100% efficient. So, transferring metal to water (engine) and then water to air(radiator) has double the opportunity for thermal inneficiency, not to mention the drag of the pumps.

As for the idea that hundreds of people cannot be wrong...note that not one single solitary aircraft mfg uses a car conversion. So I guess those thousands of engineers, not to mention managers, who face real consequences and liability for their choices are wrong.

I guess I chalk it up to "unthinking modernism". I read people referring to the "lycosaur", and extolling the benefits of modern fuel management. However, all of those advances are for operating requirements which are simply not present in a prop plane. Which is why the egg burns as much and typically a little more fuel, per speed, than does the lowly lycosaur. It is also why, even given all the best aeronautical engineers, designers, and tons of testing, a Fadec only improves the economy of a lycoming by 15% at most.

As for simple operation....the same people who joyfully get rid of a mixture knob are equipping their planes with multiple EFIS and Autopilots....the accident reports will show that mixture knobs are not that complex, but avionics are. Do we really have pilots who cannot operate their engine? Should those pilots be allowed to operate the infinitely more complex flip flop radio?

A competant pilot with an old lycosaur, can cruise all day at 175 knots and less than 10 gph (Dan Checkoway). No subaru to date can come close. While the lycosaur is cruising faster, on less fuel, and much less weight, it probably also has half the internal engine and external accessory parts. Probability of failure is the square of complexity...so......why would you spend the money to go slower, on more fuel, with more weight, and extraordinarily higher risk of failure? To eliminate a mixture knob? Or simply to prove how much smarter you are than all those old lycosaur engineers?

ship
05-06-2005, 02:44 AM
Nice debate,

Nice write up/summary from Ship,

Question for "Ship":
Ship, could you shed more light on your statement?

IMHO: Everyone should read JConard's post above... he has it right

I've worked closely with DeltaHawk since OSH '02. Details below if anyone's inclined to read through all this drivel.

(This is not a pitch "for" DH or "against" anything else....as you'll see below)

Side note: My opinions re DH being "the only diesel with commercial potential" were formed PRIOR to my getting involved with the company....i.e. that's what LED me to get involved with them in the first place.

Being involved with DH has afforded me the opportunity to examine every "aviation" engine that exists and hear about every engine that doesn't.

Myth: $20k for an "ancient-design" Lyco/clone engine is a rip-off
Fact: there's FAR less profit in a clone than you might think.

I've been an "engine guy" since before I could walk. Engineer by training (hated it). Business guy by profession. Raced a lot. Busted/fried more engines than I can count.

When I started building my RV8, I was naturally VERY interested in every engine on the market or those in the pipeline. Especially the auto conversions.

I read/heard all the stories about Lycosaurs, stone-age, etc. Also QUICKLY found/heard all of the "modern" engine offerings. Some made sense, some were total ****.

Looked at rotaries, turbines, subies, chevy's, radials, etc.....everything
I looked deeeep into the "RV turbines" as a potential investor. 'Nuff said.

The Superior/ECI clones became my favorite traditional engines.
The Egg-Subie became my favorite choice of all non-aviaiton engines.
DeltaHawk became my choice for "new" aviation engines.

The DeltaHawk attracted me for one reason: they had the design that was closest to the pure aviation mission. I also immediately liked the execution, i.e. strict discipline to the KISS philosophy within the design compromises that MUST be made for EVERY engine/mission combination.

I offered my help on the business side along with my engine "knowledge" and another set of engineering eyeballs.

Even so, the DH is very much an experimental engine for now. FAA certification is only part of the story. Proper FWF development at the OEM level is a LOT of work. Fleet hours need to be accumulated, etc.

Bored yet? Read on.

Like most specialized industries, the engine "world" is small. Take it a step further: the aviation engine "world" is microscopic.

To put it mildly, everyone in the "airplane engine" biz knows everyone else.

Everyone closely guards their "stuff" but we all talk to each other at the shows and keep close tabs on what's happening. We all eyeball each other's engines VERY closely and ask highly detailed questions, most of which are answered quite openly.

Bottom line: it's pretty hard to fool anyone for very long in the engine world. The "real" are quickly separated from the "not real". Suffice to say I will not trash anyone publicly regardless of my well-founded opinions.

Lest anyone get the wrong idea: It doesn't mean the engine folks all "like" each other. But there is a healthy respect among most of the various competitors (but not all :rolleyes: ).

How does all this all relate to "traditional vs. alternative"?

If you think THESE debates are "endless" on these forums, you should hear it among the engine vendors!!! :eek:

The ORIGINAL premise of this thread is EXACTLY on the money: do you want to "fly"? or do you want to "try"? There is no "right" answer to this question.

Like most engine debates in experimental aviation, this one has veered into muddy waters by mixing unrelated elements.

Too often these "engine debates" fail to separate "quality" from "design".

The other problem is separating "garage" knowledge from true expertise.

KEEP THIS IN MIND: If you chose an RV, you are NOT an "experimental" builder ... you are a KIT builder of a VERY CONVENTIONAL aircraft with conservative design elements.

10,000 people chose RV's because they represent the best combination of compromises in the history of aviation. Same with Cessna. It's no coincidence. They got it right.

Same goes for engines. There's a REASON that Lycoming is the dominant engine in GA. They got it right (design).

This discussion boils down to "aircraft vs. non-aircraft" engines.

Underneath all the debate, the MOST important element in ALL engine design is "suitability", i.e. what is the BEST combination of COMPROMISES for a given application taking into account all of the requirements.

The mission ...and this alone...leads to the final design choices of any engine (or airplane for that matter).

As others on this thread including me have stated, Engines are Engines. There really is NOTHING new. It's only the APPLICATION that's "new".

Translation: there is a REASON that what works is what works, i.e. it's ALL been done before. There are BETTER ways to MAKE engines, and better CONTROLS, better MATERIALS, etc. but matching the DESIGN to the MISSION is the single best predictor of long-term success.

Did anyone notice that Honda's engine looks suspiciously like a "modernized" Lycoming/TCM? The core "design" is exactly the same with more sophisticated peripherals.....just like our modern car engines are still identical "designs" to those from 75 years ago.

I can GUARANTEE that Honda would probably design the same thing from scratch if they never saw an airplane before.

I know people don't want to hear this but here goes: It's VERY easy to make the case that a "crappy" Lycoming is a better AIRCRAFT engine than a state-of-the-art japanese/german/etc. car engine.

BMW started out life making airplane engines. The BMW 6cyl is the smoothest piston engine in existence by far. Bulletproof. Would I put one in my plane? No.

Does that mean a Subie is a bad choice? NO!! It simply means that it may not be as reliable/durable/efficient in an aircraft as it was in a car. It wasn't designed for aircraft, it was designed for cars. There's no free lunch.

The Subie is probably the closest to an aircraft engine that a car engine can be.

Like taildragger vs. nosedragger, it all boils down to your particular mission priorities and comfort level.

Do your homework. Make your choice. Go for it.

I could go on for hours.....but I'll spare everyone any further pain.

In the next installment :D , we'll talk about the concepts that are most important to aviation engine design and why they are VERY different in car engines.
-- specific output
-- duty cycle
-- mission-matching
-- the "complexity matrix"
-- the "durability paradox" (no, it's not the Probability Engine)

FUN FACTS:
marine diesels
-- world's largest engine 3,000 tons
-- world's most powerful engine 100,000 hp
-- world's most efficient engine .27 BSFC
-- world's largest crankshaft 100 tons
-- world's biggest piston 10 feet long
-- world's slowest engine 50 RPM
-- world's biggest oil change 1500 gallons
it's all the same engine!! :eek:

RudiGreyling
05-06-2005, 03:02 AM
Thanks Guys,

As a newbie I like the debate, I am learning a hellaofalot lot in a short space...keep it going, and keep it clean, no low blows!:D

Regards
Rudi

rv6ejguy
05-06-2005, 02:45 PM
Well the statement above that no manufacturers use auto engines is not true. As I said before, you people not directly involved in auto engine conversions assume a lot but sometimes don't know. Rotary Airforce up here in Canada has sold over 400 RAF 2000 gyrocopters over the last 10+ years. Every one is powered by a Subaru engine. High time airframe has 2500 hours on it, fleet has around 100,000 flight hours. I have not found any internal engine failures as accident causes on these.

Of course Sube engines have not accumulated the millions of flight hours that Lycs have because only a few hundred are flying and mainly in the last 5 years. The only sane thing to say is wait and see. Saying these engines are unsuitable for aircraft use is based on feelings and emotions, not facts. Show me some facts that Subes are breaking cranks or rods. We know that Lycs have their problems even after 40+ years of trying to get it right. Look at the Ads still being issued on them and the lawsuits. Problems with supporting systems cause most auto conversion failures on Subes, not the core engine. The same thing applies to Lys and carb icing. Design a good system, use it correctly and you won't have too many problems.

The Lyc has proven to be an acceptable engine to power light aircraft however they are not cheap, they do break sometimes they do shake etc. The Sube and Wankel have also been proven to do the job but when small private companies have to foot the bill for engineering a total firewall forward package so that the masses get a reliable powerplant system in small quantities, things take time to test and longer to prove. Give credit to people like Eggenfellner who test and develop these engines to give others an alternative to the Lyc if they want it. Don't slam everyone who tries something different. Experimental aviation is just that. If nothing new is ever tried, we'll always be flying the same old stuff. We have to start this development somewhere and improve as we learn.

As for all you guys breaking race engines. You must have the wrong builders or be overrevving them. I have built over 200 performance and race engines, mostly turbocharged road racing 4 and 6 cylinders. None have ever broken a rod or crankshaft even producing over 200hp/ liter at 8500 rpm. You just gotta know what you are doing and choose the right engine to start with.

We used to here the same thing from the large displacement- slow turning guys- "you high revving turbo guys will never finish the race" within 1 year we were on pole, 2 races later we won. That next year we won the championship with 6 more to follow. Then they wanted to ban us because it was unfair! Same thing happened in F1 and IMSA. There are teething problems to solve but with hard work, it can be done.

My RV6A weighs 1140 lbs. empty and will true 182 knots with a Sube at altitude. Not too bad considering the that the prop cannot absorb anything close to full power above 10,000 feet. With further R&D, no doubt weight, speed and fuel burn can be improved. Recent leaning experiments have got the SFC into the .42 range which is equal to the Lyc. New radiators may allow a reduction of 15-20 lbs. from the airframe and a further reduction in drag. This is my first attempt. Our new RV10 will be powered by a twin turbo Subaru EG33 applying all the lessons learned on the -6A and te EJ22T.

Jconard
05-06-2005, 03:34 PM
First,

I hate to call you out, but no major, open wheel road racing series I can think of has allowed turbocharging for years, unless you mean to say you built engines for F1 or CART....is your name cosworth?

Second those 8500rpm (slow) and even 12,500 rpm engnes (formula atlantic or supervee) will break if not freshened after EVERY race weekend....same with the racing subes, at least at high specific outputs. As for engine builders...these guys know what they are doing, the annual budget for a club racer in F2000 is more than half a million and double that for a formula Atlantic or Super Vee effort. You cannot spin an engine at high specific output evels all day, and at high rp, without constant maintenance. Lasting 2000 hours? forget it, those engines don't see 100 hours in two seasons of racing, but they will be rebuilt 20-30 times in that period.

Third, a gyrocopter is not an airplane and does not have the same stresses.

Fourth, nothing I have said is emotion. I road raced for 13 years. I am simply pointing out that the things we needed for that mission are innapplicable, and unnecesary for driving an airplane.

Fifth, the beauty of slow turning, in an airplane is that while inertial force is directly proportional to mass, it is exponentially applicaple to speed/acceleration. In other words, the stresses are high.

182kts at altitude? nice job with a complex turbocharged conversion, but still slower than an angle valve 360 normally aspirated.

The best part of a car engine in a race car is that when it blows, you simply pull over. You do not crash into someones house. A high wing loaded, constant speed prop sport plane, with an engine failure, is coming down NOW, and fast.

Again, why is it that in 100 years, with the plentiful supply of auto engines, and countless dollars spent, the lasting, light, and good performing packages are still normally aspirates, air cooled, slow turning, direct drive engines?

hecilopter
05-06-2005, 04:14 PM
I too have been through the decision making process of what to power my RV-7A with. I convinced myself both ways at least 3 times (Superior or subie). Money had a lot to do with my decision, time another. In the end the subie
1) didn't cost any less,
2) had much longer wait time to get and
3) even though there are lots of people using it, I still have yet to see the overwhelming majority of people rushing to use it. Meanwhile I wanted to get finished and fly.

My choice, I wound up going with Superior (any other lyc alternative would be just as good). They HAVE made some improvements to lyc's old design and the Hartzell propellor I chose to go with it was TESTED to be a match with the pulse power strokes and approved (with mags). And in the end it was cheaper. I went with the 8.5:1 pistons to have the OPTION of using MoGas if I ever need to. That way I won't be left out in the cold at the end of 100LL(?) (I personally believe 100LL will probably go away someday, but they will probably come out with a replacement (unleaded) fuel we can still use.)

My 2 cents on a "perfect" aircraft engine:

While not available now, fuel cells and battery technology will improve in the coming years (esp. with fuel prices escalating). An ELECTRIC aircraft engine would be perfect. It would have few moving parts, be turbine smooth, VERY quiet, and would have the same power output at ANY altitude. Backup batteries could add to reliability. Wouldn't want to fly it near a thunderstorm however, a lightning strike would ruin your day :)

rv6ejguy
05-06-2005, 04:22 PM
Again, you assume. I did not say that I raced open wheel cars or built engines for them. I built and raced closed wheel cars. Then engines had to last for the whole season. I never said a race engine was going to last 2000 hours. The maintenance between races was to check valve lash, compression, leakdown and make sure all the exhaust system bolts were tight. The same Mobil 1 oil was used for the whole season. One Toyota engine went 4 race seasons on the same set of bearings, same pistons, same rods, block, crank, head, valve job, turbo. Just rings and gaskets for 62 races. 47 class wins. 360 hp at 7750rpm out of a 1.7L 2 valve pushrod engine.

I am not advocating building a fire breathing 2.5L STI based motor to jam out 400hp at 8000 rpm for RVs. I could do it, but you are right, it would probably last 100-200 hours and run the tanks dry in an hour. Not very practical. We run most of the Subes at 4400-4800 rpm. With the turbo, we never run ours over 4600 which keeps inertial stresses lower than an atmo version. We only run 38 inches for takeoff and 35 for climb, 30 for cruise. This does not stress the EJ22T as it was engineered to do this from Fuji.

The stresses are HIGHER on a Lyc at 2700 rpm if you work the math and use the reciprocating weights of the components and the piston speeds. The EJ22 stroke is only 75mm. Piston speeds largely determine the rev capability and stresses on engines. F1 engines turning 18,000 rpm have many small pistons and extremely short strokes. 4600 rpm for the Sube is no harder than 2700 on the Lyc. It just sounds scary if you think in Lyc. terms. Rotax's turn 5500-6000. So what, they work because they were designed that way. The EJ22 is designed to run at a maximum of 6250 rpm. Factory redlines are set conservatively to ensure that if someone in Germany wants to cruise flat out from Munich to Stuttgart, they can. If the engine was fundamentally incapable of running at such rpms continuously, wouldn't those 3 Legacy's that set the 100,000 km speed record running at 6000-6500 rpm for 400 straight hours all have grenaded? Again, I say show me some facts that Subes blow up running at 4600 rpm in aircraft.

Even Van's is eyeing developments like the Egg Subes and the Powersport Wankels with interest. They have openly invited anyone to come down to Aurora to fly against their Lycs. Powersport has, some Egg boys are about to and some NSI guys have also expressed interest. Van's is not saying that auto conversion can't do it. They just say we reserve judgement until we see it with our own eyes. Even then, they are likely to recommend Lycs as a first choice until the FWF companies have 10s of thousands of hours built up.





A gyro turns a prop through a redrive just like in an RV. I'm sorry if you don't see the similarity here???

182 knots and we only have 134 cubic inches and we are just getting started with a prop not even close to optimal. I don't think that's too bad.

szicree
05-06-2005, 04:45 PM
Seems unfair to mention the number of AD's on Lycs since auto engines have no such requirement. Actually, the fact that there is no system in place for disseminating such info is another reason to be cautious about auto conversions. Is Sube going to inform us if they discover a metalurgic issue with cranks produced many years ago? They most certainly will not because of the legal exposure.

I admire the ingenuity of those who've adapted these motors to planes, but I think the key word here is ADAPT. Why mate a hi revving engine to a system that likes to turn slowly? Can somebody tell me WHY??

Also, I notice that the Rotary Airforce website says their Subes have 1000 hour TBO, while Eggenfellner says 2000. I'm sure the Egg setup is a triumph of fabrication, but their FAQ page seems to rely heavily on answers of the form "we've never seen a failure, so it must be strong" to answer questions about reliability. I'm kind of a science type of guy and would like to see some more controlled test data instead of user testimonials.

gmcjetpilot
05-07-2005, 03:07 AM
Most info is covered on the first 3 pages of this thread. There is no need to re-state the obvious or need to defend auto-engines or Lycoming. The numbers speak for themselves. To touch on a few points:

Talk is nice but here are some hard numbers. Van's aircraft compared two RV-8's, both with Rotary engines from power sport and 3 blade MT props.
http://www.powersportaviation.com/
They are based on a highly modified Mazda B13, which is an outgrowth of the late Everett Hatch's work. They are beautifully designed and produced. These two RV-8's were flown side by side with two other factory planes,RV-8's, one 180hp RV-8 (Dilbert) with a new blended Hartzell and the other IO-360 200hp RV-8a (Tweety) with standard Hartzell. The findings were the rotary burned more fuel and was louder and heaver than either Lycoming powered RV-8. No big surprise. The rotary did well with time to climb and top speed at 8000 feet. Top speed of the faster of the two rotory RV-8's was 3 MPH faster than the 180hp Lyc Dilbert. Time to climb was 15 seconds faster than Dilbert. The rotary burned 7.1 gal vs. 4.6 for Dilbert. Next, was a close course takeoff-climb-cruise-approach and land; the rotary burned 12.9 gal vs. 8.9 gal for Dilbert. (Note: Dilbert has a pre-production FADEC and Tweety had a tired IO-360 (200HP). Dilbert 180hp (RV-8) was faster than Tweety 200hp (RV-8A), part in due to the tri-gear, older prop and the high time 200hp engine down on power. I called and asked Ken in Van's engineering dept. I must admit the rotary is putting out at least 180hp and matching the performace of the Lyc but with some cons: cost, weight, fuel burn, noise and longer build time. I think that is still pretty good because most auto conversons have all the cons but also have lower performance. It is one thing to say my engine makes 200 hp and another to get that to the prop. (like the Subie: Higher cost, higher weight and longer build time for less performace; Pros: Subjective smoothness and less noise). At least the rotary is up to snuff in power. Remember this is a highly modified custom rotary and is only partially based on a Mazda B13. A Mazda you convert will not perform as well, may be closer to a 160hp RV, however you can still expect the fuel burn and noise issue. The plus of the do it yourself is lower cost, but at the trade time and sweat. Performance likely will not be as good as a powersport engine, but they (powersport) are out of engine production at present. I know Tracy Cook is now developing the new three rotor Mazda engine under build for many years. We shall see. Tracy Cook is a straight shooter and realistic. Don't get me wrong I love experimentation, but that is the point. If you want to fly get a Lycoming. If you want to be differnt, experiment and tinker than an auto engine might be for you.

Bottom Line, Tracy Cook and builders using rotary engines are doing a great job, but rotary engines will always be louder, more thirsty and have more "systems": radiator, pumps and electrically dependant fuel pump/ignition/fuel injector (engine computer), which reduces reliability at least from a statistical standpoint. Mechanical fuel pumps, mechanical fuel injection, carb and magnetos or self-powered electronic ignitions are going to be more redundant and reliabile. This is where people might confuse "Farm tractor" technology witha Lycoming, but it works and simplifies the installation.

Subaru: Great cars and as far as an aircraft engine, so so. It is just a horizontally opposed four-stroke internal combustion water cooled gas engine with overhead cams. No earth shaking technology. It is small displacment with tiny pistons so it is a higher reving engine. Again not big deal, we know turning an engine faster makes more power. The bad part is you need a reduction drive becaue props don't like to be turned too fast or they go supersonic at the tips and loose efficency. The cubic inches are half of what a Lycoming is. The Subie will be working hard to keep up. Let the numbers speak for themselves again. Subie RVs weight at least 100lbs or more than a Lycoming powered RV, and the Subie has the performance of a 150/160hp RV at best. You are stuck with very expensive electric props because a fixed pitch would really limit the performance even more. Hydraulic prop is not an option and fixed pitch would reduce the RPM dependant power plant. Also the reduction drive adds more complexity, even if they claim 100% reliable, there is nothing 100% that is mechanical. Also you will spend way more to get an Egg-in-Kit than an O-320. Buy an O-320 and use the stock off the shelf Vans kit parts and install with off the shelf installation components and be done with it. The airplane is designed for a Lycoming after all. Much simpler systems and higher resale. Why resale? Reason, any mechanic at any airport can work on a Lycoming and has parts and tools. That does not apply to a Subie. Most people buying a second hand RV will likely need to farm out some of the maintenance and 100% of the condition inspection to an A&P (mechanic). An A&P may not want to deal with an auto engine they are not familiar with. Again LET THE NUMBERS SPEAK, higher weight, cost and lower performance than a Lycoming. The only Subie that I saw match a Lycoming was a custom well designed turbo charge Subie and that did not start becoming an advantage until above 11,000 feet, and then by only 1 mph or two. To use a turbo you better get an O2 mask. PS, A Lycoming can be turbo charged also and I expect the Lycoming would still out perform the turbo Subie. Why? becaue the Lycoming and its turbo are designed for aircraft use, not car use.

Last the Lycoming and clones are not hammered out by a black smith on an anvil. They don't shake like crazy. A well ballanced prop and all 4 cylinders producing even power will produce a very smooth ride. Turbine smooth? No. With all due respect to those who extol the virtue of auto engines don?t know what goes into an air-cooled horizontally opposed engine. They are purpose built to directly drive an aircraft propeller at low RPM, high torque, low weight with integral prop hydraulics and accessory and fuel pump drives. If you were to design an air-cooled aircraft engine today, that would fit into to today?s aircraft cowls it would look like a Lycoming. 4 stroke technology is not new and innovations for cars has to do more with fuel economy from the electronics than the internals, or at least internals of a low RPM, high torque engine. Auto engines operate in a wide range of powers from idle to full power and typically operate at a low (%) power on a continuous basis. Asking them to do 100% for extended periods is asking for a lot. Overhead cams and multi valves and are not necessary in an engine turning a constant RPM with a max of 2,700 RPM. Of course the approx max prop RPM is around 2,700 rpm, which is no accident. Again aircraft engine engineered for aircraft and direct drive of a prop. Spinning your engine faster and making more power on smaller displacment is not new. There are many geared aircraft engines.

An aircraft air-cooled engine uses very high tech materials and modern machine processes. Some tolerances are extremely tight and the appearance of a cast case should not make you think it is crude. In fact the case halves have flatness and positional tolerances as tight as found anywhere in any engine. If you want modern fuel injection and electronic ignition or turbo charger or even FADEC you can add it. As far as reliability of a Lycoming and tracking of engine problems that speaks for it self, 60 years of service and millions of flight hours. WWII and pre & post war research (NACA/NASA) developed technology that is incorporated in our little aircraft engines. Also new inovations as cam oilers and roller cam followers are now being introduced to Lycoming. With the mass total number in the field over 60 years, failure rate is very low. Catastrophic failures are rare. The ones that do occur are offten from poor maintenace or abuse factors. Failures from no where are even more rare, not withstanding the batch of bad cranks a few years ago. However auto guys need to prove something and point to a RV accident in Oregon a few years ago with a modified rebuilt Lycoming. I have nothing to prove but before you plunk down almost $40 grand for a Subie kit and electric propeller look at a new Lycoming and a Sench fixed metal prop, engine $19K, Prop $2.5K and installation kit $2K= less than $25K. Now price a Subie kit. Don't forget you will need a prop that cost almost 10 grand. Also with all the extra plumbing in the aircraft you will spend more time with the installation. Also check what a Subie powered RV sells for. How many auto conversions have failed due to engine failure? Don?t know. The tracking is somewhat hit and miss, but the ones I have read about were caused by their more complex support systems, belts or total reliance on electrical power. With so few flying over a short period it remains yet to be determined how the reduction drives, bearings, crank, rods, pistons and valves will do in service. These engines are running at +6000 RPM in planes. My old Subie would turn 2,500 RPM max on the freeway.

Just don't get hyped the the Lycoming is crude or inferior. Weight is a big deal in a little plane. 100 lbs to the gross weight is unacceptable. At least the rotary is only 30-70 lbs more and matches the 180HP Lyc, which is very good. You still have the expensice prop to buy. Again, if you want to fly, go with the engine the RV was designed around , the Lycoming. If you want to be differnt and experiment than the auto engine may be great for you, but know what you are getting involved in. Also check to see if you can get it insured with an auo engine if that is your plan down the road. :)

Cheers George

rv6ejguy
05-07-2005, 11:32 AM
Nobody here on the auto side is saying that the Lyc is a piece of junk. Nobody here is saying that the comercially available auto conversions are cheaper than the Lycs and their clones. Nobody is saying that they outperform a Lyc in speed or fuel burn. I state all of this near the end of my recent article in Kitplanes where I tried to be as subjective as possible in the comparison. If you want the highest payload, good speed, good fuel burn and lowest cost, a Lyc clone is the best choice, no point debating that.

The big thing you are missing is that not everyone has the same priorities for an engine. Smoothness and no fuss are big on the list for many who have chosen the Sube or Wankels. Lower fuel burn at reduced power settings seem to be important for others with the Eggs. But I think the biggest thing is that not everyone wants a 5L Mustang which is what a Lyc powered RV is. It does the job well, is well proven but everyone has one. I like something technically different and I suspect many other Sube and Wankel guys also do. If you like Lycs, by all means fly them and enjoy them. When I land somewhere, everyone wants to know all about the turbo Sube under the cowling and comment on how nice it sounds. They couldn't care less about the other two Lyc RVs parked next to me because they've seen it all before.

The initial costs may be high for a conversion but the overhaul costs are MUCH lower than a Lyc. Figure $500-750 for the DIY and maybe $1500-$2500 if a Sube or Wankel is redone professionally. Even if the TBO is only 1000 hrs., this looks good for people who fly a lot. My hangar mate just dropped $6000 to buy 4 new jugs, 4 exhaust valves, pistons and rings, gaskets etc. for his O-360 with just 1300 hrs. TT. (Low compression, high oil consumption on 2 holes and broken rings found). This engine was flown carefully with proper maintenace for its whole life. There are advantages and disadvantages to both engine types.

Statements like the Subes running at 6000 rpm are just not true. Egg runs a max of around 4900, I run 4600 on mine. This is JUST like a Lyc running 2700 as far as stresses and wear go. Just because you drive at 2500 rpm has NOTHING to do with the fact that these engines happily run at 4600 rpm for very long periods. This IS proven and since nobody here has stepped up to the plate with evidence to the contrary, maybe it's time to quit harping on it.

In fact, any good, modern engine is capable of this. One of my friends raced a stock 4AGE powered MR2 in edurance racing series all over North America. The engine had 25,000 miles on it when he bought the car and he put 45,000 RACE miles on it over the next 6 years. WOT, shifting at the stock redline of 7500 rpm. It was never touched in that time.

Wankel and Sube conversions are in their infancy and there is still much to be learned with redrives, cooling and weight reduction along with ECU tuning, props and blown aspiration. We in this field are working to improve these factors plus hp and fuel burn and we are making these aspects better. You will see improvements in the coming years. Tracy Crook and Ed Anderson are finding better fuel specifics with extensive leaning- something the Wankel seems to take well to.

Lack of a good, inexpensive variable pitch prop is a major issue with auto conversions. Can't blame that on the engines. Some developments here are in the pipeline. NSI claims some great performance from their CAP equipped Subes but we'll have to wait and see how they compare against Van's demonstrators.

Supporting systems such as fuel, ignition, radiators, alternators and dual batteries receive a lot of attention with auto conversions and rightly so as these cause the majority of "failures". Several groups post flight proven designs for others to follow to avoid possible problems.

The atmo Wankels do have the high noise level problem to contend with and much muffler development has taken place. The latest idea is simply to mildly turbocharge them. This makes them very quiet, improves power to weight ratio and altitude performance and reduces rpms required across the board. Some like John Slade in his Cozy are doing much good testing here. I am of the same opionion with the Subes- turbo is the way to go with higher CRs to get better fuel specifics and keeping the noise low. Working well so far, just need a better prop to make it all come together.

szicree
05-07-2005, 01:55 PM
But I think the biggest thing is that not everyone wants a 5L Mustang which is what a Lyc powered RV is. It does the job well, is well proven but everyone has one. I like something technically different and I suspect many other Sube and Wankel guys also do. If you like Lycs, by all means fly them and enjoy them. When I land somewhere, everyone wants to know all about the turbo Sube under the cowling and comment on how nice it sounds. They couldn't care less about the other two Lyc RVs parked next to me because they've seen it all before.

I think you've hit the nail on the head here. It's the same as using a Nailhead instead of a chev 350 in a hotrod -- just something different and interesting. We all love to see these individualists do their thing. Keep it up rv6eguy. As for me, I'm sticking a IO360 in my Tacoma : )

gmcjetpilot
05-07-2005, 02:08 PM
Dear rv6ejguy: I agree with you but detect a little defensiveness. No need, you make real good points and agree with you 100%. Obviously I have a Lycoming, but I have been in experimental aircraft for 15 years, and following alternate engine developments the whole time.

"Nobody here on the auto side is saying that the Lyc is a piece of junk. Nobody.........."
Yea some do, especially when selling something, that is the first thing that gets mentioned, but I don't really care because the performance and history speaks for itself. Folks like Tracy Crook (rotary) are real straight shooters, and others that were making some claims have backed down. Could a Lycoming be better? Yes, after the 1950's piston aircraft engine development slowed with the Jet age, but now there is a new wave of developments in better fuel injection, induction, ignition (electronic), FADEC and roller cams. All this is thanks to the experimental aircraft market. Plus we have 3 manufactures for parts now. Subie has just one. Is an air-cooled Lycoming more sensitive to poor operating practice than a water-cooled engine? yes, but it's not a difficult thing to operate within the limits for long life (like CHT400F max, oil Temp 190-210F), lean properly and operate frequently. Sitting and corrosion is a big killer. Like anything there are trade offs and limitations. With Lycoming, it is CHT, frequent oil changes (25-50 hours) and long periods of dis-use.

"The big thing you are missing is that not everyone has the same priorities for an engine. Smoothness and no fuss are big........."
I agree, but a Lycoming is not rough, and preventive maintenance, oil changes and plugs, is all my Lyc engines have required, past and present. Yes they shake, but some people put on 3 blade composite / wood prop on their Lyc and swear they have died and gone to heaven. Still, with big piston power pulses? hanging off 4 little rubber mounts and a prop spinning on the very end, something is going to moving. Also as far as fuel efficency, the Subie is not better. There is no substitute for physics. All gas engines operate within a limited range of efficency. There is no free lunch. One way to way to improve efficency is increase compression. In a Lycoming with a coffee-can size piston you need to be careful with high compression, but it can be done with care. Super charges or turbo charges is the other option. Diesels are more efficient simply because they operate at very high compression ratios, but they are heaver engines (or should be) to take all that pounding. Deltahawk Diesels? Smooth? Fuel savings? Installed weight? Cost??? We shall see. Numbers speak.


"The initial costs may be high for a conversion but the overhaul costs are MUCH lower than a Lyc. Figure $500-750 for the DIY and maybe $1500-$2500 if a Subie or Wankel is redone professionally..."
Agree, overhaul cost is less, but will that offset the initial cost and expensive prop? A Pro Lycoming overhaul is around $10-$12 grand. With the wide availability of parts from ECI, Superior and Lycoming, part prices are not bad. You can buy a whole new cylinder assembly, piston, valves etc for a grand. If you do-it-yourself you can overhaul a Lyc, parts, machining w/ accessory overhaul farmed out for less than 8 grand or $4 bucks an hour, or the price of one gal of gas(almost). :eek: Also, you can buy a new Lycoming, fixed prop and all accessories for $18,000, new everything. Installed w/ prop for as little as $23 grand, giving you 10-20 years of flying before it's first overhaul. If you are a good bargin hunter you can save a lot of money buying some used components, but you have to look. The rotary guys have the best do-it-yourself program with builder support, books and critical parts availability (Tracy Crook). I think the price is around $12 grand with a fixed pitch prop and a lot of work for a home grown Mazda engine.

"Statements like the Subes running at 6000 rpm are just not true. Egg runs a max of around 4900, I run 4600 on mine.........."
I stand corrected I was thinking of a Mazda, but 4900 is still almost twice what I turned my Subie car on the freeway. Guys who work for car manufactures destroy engines by running them wide open all the time for a living. Fact is car engines do live at less than 30% of their rated max output most of the time. They only get up to rated HP for short periods. Does it mean they can't do the job in a plane? No, but as you said use of these engines in aircraft is realitivly new. We shall see.

"In fact, any good, modern engine is capable of this. One of my friends raced a stock 4AGE powered MR2 in endurance racing series all over North America........"
Amazing, agree no doubt car engines are reliable. As I said we shall see how the auto engine fleet does over the next 20-40 years and 100,000-million hours.

"Wankel and Sube conversions are in their infancy and there is still much to be learned with redrives, cooling and weight reduction along with ECU tuning, props and blown aspiration............."
Agree, it is all very experimental. You have present facts very well and agree with you. They are improving and my big pet peeve is the cooling drag. Clearly the radiators in an auto engine set up are "add-ons" and work-arounds to the existing RV cowls for air-cooled engines, except the powersport rotary engine cowl, which I think Sam James makes. This is a step in the right direction. Clearly the P-51 had the idea long ago of using a belly scoop and special baffles, ramp doors and "diffusers" to reduce cooling drag. The NACA design paper I think is de-classified and you can get it on the web somewhere?

"Lack of a good, inexpensive variable pitch prop is a major issue with auto conversions............"
Yep, and electrical props will be more always be more cost & maintenance with a slip ring and brushes. Reliability? Hydraulic props are fly them and forget them in my experience. Also aerobatics may not be as satisfying as a hydraulic prop, in that they act much faster. The electric prop may not be able to keep up and RPMs may vary. Again like everything there are limits and trade offs.

"Supporting systems such as fuel, ignition, radiators, alternators and dual batteries receive a lot of attention with auto conversions and rightly so as these cause the majority of "failures"......."
It will always be a concern. It would be a good test to take a Subie or Rotary up and dump the coolant and see if it can last long enough to get you on the ground. Any takers? My family had an early Mazda RX-3 rotary engine car in the 70's. It got overheated once and melted the O-rings. I guess they are better now, but still I don't think they like to be overheated. I would guess if the FAA was certifying a water-cooled engine today, it would have to be shown loss of coolant would cause no hazard, is redundant or it could never happen.


"The atmo Wankels do have the high noise level problem to contend with and much muffler development has taken place. The latest idea is simply to mildly turbocharge them............"
Great idea, look forward to seeing the real experimenters do this unlike us lazy bolt'er-up Lycoming and go fly guys. :D Even a Lycoming can be quieter with a muffler. The only problem is people don't want a "swiss" muffler hanging from the bottom of the plane half way to the tail. They are about 4 to 5 feet long. In Europe they have no choice, like in Switzerland. I have a 4 into 1 exhaust system on my RV-7 O-360 with a 19.5L" collector. It would be so easy to extend back another 21" with a aluminum or stainless steel round racing muffler. It could be made to remove quickly for speed and replaced for cruising. These off the shelf mufflers are small , light and the correct 19-21" length multiple needed for "tuned" savaging. Once I get my current project flying, I may experiment with this. I think a lot of the "noise" and vibration felt in RV's with a Lycoming is the pounding of the exhaust on the floorboards. It will be interesting to see how much reduction in noise I get and at what loss of speed from the extra appendage hanging down. What about an augmenter fairing to scavenge air out of the cowl. This shows even a Lycoming installation can be improved, such as a sealed pressure plenums (been around for 40 years plus) and small laminar flow cowl inlets developed by the U of Mississippi on a NASA grant in the 70's, first used by LoPresti, like the Sam James cowl.


So experimental improvement is not just not for the auto conversion guys. You can still have a Lycoming and "play" with ideas and be differnt. In the last 10-15 years-Lycoming: 4 into 1 exhaust, better electronic ignition, FADEC, Roller Cams, modified cam profiles, HC pistons, differnt piston ring and cylinder materials, aftermarket fuel injection, **liquid cooling, composite engine oil pan and better engine instrumentation to name a few. The Lycoming is not that old fashion.

Cheers George, big fan of auto engines and builders that try it, but have a Lycoming for now. :D

**The best thing about Subie and Mazda engines is they are liquid cooled. Liquid does have advantages. The bad part is adapting the heat exchanger to the airframe, especially ones designed around aircooled engines. What if the Lycoming were liquid cooled. Here is an interesting link below.
Cool Jugs-Liquid cooled cylinders for Lycomings (http://www.liquidcooledairpower.com/cj-pricing.shtml)

rv6ejguy
05-07-2005, 08:06 PM
You make some fine points here. I'm not defensive, just one to set the records straight with facts from 25 years of real world engine building/ racing and flying a Sube powered RV. I try to tell it as it plays out, bad or good. I just don't like to read **** put forth by armchair "experts" who have no experience in the field of auto engines or flying them, any more than you want to read foolish propaganda from the auto contingent about how much better auto engines are than Lycs.

Yes, some auto guys slam the Lyc but like you say, there is little factual info to back up the wild claims made by many. I have battled with a couple manufacturers of auto conversion who had completely false information posted on their sites. They have since removed this nonsense.

I'd have to disagree that the Sube is no more smooth than a Lyc. The Egg owners and people who have flown in them- even die hard Lyc owners- say that they are way smoother.

I didn't mention the auto fuel thing earlier. Many guys are running this to save money over 100LL but hauling fuel is not on my fun to do list.

The idea with the Subes is there really is no preventative maintenance. Check the oil and coolant and go, just like a car. Plugs are checked every 250 hours or so and oil changed every 100. That's nice for many.

High rpm use on these engines IS proven with 100,000 flight hours on RAF EJs 4000-5500 rpm, 100,000 km world speed record flat out for 14 days straight at 6500rpm by Subaru and Egg's fleet racking up more hours every day along with others.

I agree that new technology is showing the old dog new tricks (Lyc) and I've seen some pretty amazing reductions in fuel flows when it all works right together. This just puts the bar higher for the auto engine guys. I certainly don't believe that auto engines will take market share from the Lyc in the next 5 years or even 10 for RVs but there are a LOT more people using auto conversions now than 5 years ago. There must be some appeal there.

The cooling solutions are something that we are working on quite a bit. The under- the- cowling rad mounting used by Egg and myself is probably not the best from a drag standpoint but good for packaging and keeping costs in line, especially with the deep spar on most RVs. Our studies show that pressure recovery is poor with such short ducts. We are testing a rear fuselage mounted rad now with flush NACA duct feed and will report our findings on our site. The RV10 project is likely to use a P51 style belly scoop for the rad with cowling cheek inlets to feed the intercoolers. The -10 lends itself much better to the belly scoop due to the central tunnel for running coolant lines.

As long as we all enjoy our flying, it matters not what is turning the fan out front.

Jconard
05-08-2005, 08:08 PM
I just don't like to read **** put forth by armchair "experts" who have no experience in the field of auto engines or flying them.

Okay, 16 years as a driver and owner in racing. 4AGE engine you talk about is what we use in Toyota Atlantic racing where they spin the RPm you describe, but need rebuilds every weekend to stay in race trim. You are the guy who claims to have built a 1.7L pushrod, 300 hp, turbocharged 4 cylinder, that won 62 races, in road racing, with no rebuilds. Please illuminate the racing series and car number. I have to call BS on that.

I agree that new technology is showing the old dog new tricks (Lyc) and I've seen some pretty amazing reductions in fuel flows when it all works right together.

Again, numbers please the Aerosance Fadec with both ignition and fuel flow gives only 10-15% efficiency boost over the range of operation. At certain points I am sure that there is no gain.


As long as we all enjoy our flying, it matters not what is turning the fan out front.

That used to be true...in the legal environment, a few smoking holes from ill conceived approaches will be the end of us all.

The sube rebuild for that money ($1,000) has got to be rings, gaskets and maybe valve guides, with the owner doing the work.

I can put in rings and guides in lyc for that money.

The $18,000 rebuild price by an aircraft shop includes rebuild of engine and all systems including fuel injection/carb, mags, bearings, etc...and inspection and re-certification of the parts.

In a car engine rebuild you simply measure the parts and send it off to a machine shop. If you could find a machine shop to do that rather than the mandatory replacement/certification schedule that goes with the Lycoming, the cost would be the same.

The only auto engine converted to airplane, and certified was the Mooney porsche. To rebuild a 911 engine to factory standards costs about what a lycoming does...but then it is built to exacting tolerances. There was never a viable busines "blueprinting" the 911 for that reason.

Remember there is an avid busines "blueprinting" the auto engines which is a process that brings them in line with their design specs...it is usually worth 10-15% HP.


There are some principles to engineering which require no data:

1. When given the choice between simple and complex, simple is preferred.
2. Probability of failure goes up at the square of complexity.
3. Heat exchange is never 100% efficient (More like 80%). Therefore the more successions of heat exchange, the lower thermal and drag efficiency. (Metal to air vs. Metal to water to metal to air).
4. Refinement of a functional design nearly always produces better results that revolution. 911 vs. RX-7. The components of the Lyc have been refined and improved with excellent materials and practices for 50 years.

No one has yet explained to me why it is more desirable to spend more for a slower, heavier, higher fuel burn engine that needs more parts and more cooling drag to do it.

rv6ejguy
05-09-2005, 12:47 AM
Yes, But you don't build engines professionally. I build the car, the engine and race them. I even built my own dyno and flow bench ( and have flowed Lyc and Cont heads on it) and have done over 500 dyno pulls here and on other engine and chassis dynos. I've built over 200 performance street and road racing engines over the last 25 years, many high output turbocharged road race engines. My shop, Racetech Engineering fielded 6 cars in various classes. My company Racetech Inc. currently builds engine management systems, sold worldwide. I am a major contributor to soon to be released the 3rd Edition of Hugh McInnes' Turbochargers book and have written other technical articles for Contact, the forunner of Turbo magazine many years ago and Kitplanes. What exactly are your qualifications in this field?

The Kent Ford engine is crappy OLD engine with the SOHC 2L not far behind. These are cast iron boat anchors. I've built a few and was not impressed with the heads, cranks or anything else about them. You are permitted to do little to these (ie proper race parts) in FF or F2000 so they need rebuilds frequently to stay fresh enough to win. These would not be a good starting point for an aircraft engine and there are many other modern engines today which also would not be good choices to start with.

I mentioned a showroom stock 4AGE here, 112 hp revving to the stock 7500 rpm redline, not a 245hp Atlantic engine running at 10Gs. I have built several atmo 4AGEs, one of which dynoed at 238 hp at 9600 rpm on methanol. This engine WAS highly modified with 12.8 to 1 Wisecos, Group A cams, 7MG valves, under bucket shims, German springs, 4AGZ block and crank, Carillo rods and 50mm SK carbs. I designed and fabbed the header and ported the cylinder head as well.

I mentioned a 360 hp 2TC engine here , not a 300 hp one. I did not say that the engine was not rebuilt in this time. It was rebuilt at the end of each season but we used the same set of bearings, same crank, same pistons, cam, springs, pushrods, timing chain, block and head casting for four seasons. Only rings, gaskets and grinding the valves and seats was required in these four seasons. We ran up to 7600 rpm on these engines if required.

This was run in the Modified Production series here in Canada in the late '80S to mid '90S. Run as a cheaper alternative to GT 1, 2 and 3 on street R compund tires. Turbos were permitted at a 1.5 factor so our 1400cc sleeved 2TCs ran against 2L atmo cars although at a very high weight penalty. Our 1700cc turbos ran against mainly Rx7s and Z cars in MP2. Most days, the 1.4 MP3 Corolla would trounce the MP2 atmo cars in the class above. There was no contest in MP2 where we won the championship 5 years straight, first with a 2TC powered 240Z, then with a 2TC powered Celica. We also ran a 2400cc 20R Celica in MP1 against SBCs. Won this championship the first year and finished 2nd the next year against a $100,000 Camaro with the same $15,000 Celica. In all, we won 7 championships in this series which was the most competitive closed wheel series in Western Canada with sponsorship from Yokohama and then BFG later. The MP2 cars ran similar lap times to the best FF1600s.

I was the chief driving instructor for the WCMA road course licensing school at Race City Speedway in 1992. I was the overall winner of the GT/MP sports car championship with more points than any other driver. No DNFs. I can send you a picture of the plaque if you want.

In 2002, a GTS Corolla running a 1608cc turbo I built, on slicks, took the outright Solo 1 lap record at RCS, running a 1:22 at only 15 psi boost. The GT1 lap record at the time was 1:15.

Anyway, that aside, blueprinting a stock engine will never add 10-15% to the hp.

For our rebuilds, we magnafluxed the rods and crank each season just like the aircraft guys. By the way, all the 2TC engines had stock block, crank and prepped stock rods. The factory hp rating on these engines is 70-88 hp depending on year at 6000 rpm. We made 5 times that! Reliably! Naturally these engines at this output level have a limited lifespan of less than 25 hours but it goes to show that even an old design like this can take some pretty extreme abuse. This specific output would equate to a Lyc O-360 putting out 1245hp! Do you think it would even last 1 second?

I simply advocate choosing a robust, relatively lightweight engine like the Sube EJ or EG series or Mazda rotary, make only the proven internal mods done for racing type reliability, turn it at a conservative rpm (say 75% of the stock redline) with mild boost and it should be very reliable. This is the formula that Porsche and Audi have used to win many 24 hour endurance races. Toyota proved that a 2.1L turbo engine could be more reliable and more powerful (over 900 hp without restrictors) than a 6L atmo V8, V12 or 3.5L F1 type Cosworth in IMSA much to the dismay of the whining Brits at Jag with their unmatched 14 wins in 15 races in GTP (they sat out the 15th race to let someone else have a try). The AAR GTP car still holds the outright lap record at a couple of US tracks I think.

rv8ch
05-09-2005, 06:07 AM
Very interesting thread.

RudiGreyling
05-09-2005, 06:59 AM
Good debate, I feel the tension coming in, we need a break...
go have a look here, for a tension breaker :p
http://www.bath.ac.uk/~ccsshb/12cyl/ (http://www.bath.ac.uk/%7Eccsshb/12cyl/)

http://www.bath.ac.uk/%7Eccsshb/12cyl/rta96c_crank.jpg

Regards Rudi

Jconard
05-09-2005, 07:17 AM
Western Canada ...

I thought you said it was road racing. When I was on the circuit, and ran into western Canadians who, like me had travelled to Mosport (In Bowmanville, Ontario), they told me there were not any road courses of consequence in Western Canada...do you mean soe kind of left turn only stuff?

And, the car rebuilds do not require certification and all that goes with it, as do airplane parts. (It would be nice to find an automotice machine shop capable and willing to do the work at the cheaper prices).

As an aside, I read the egg site again. He still does not allow a metal prop. Of course in typical egg fashion he puts the issue as "no airplane should use a metal prop because they are too heavy". It looks to me like pretty good proof that the harmonics from whipping two mettl flywheel arms are too much for the setup...do you know any lasting installations where it flew 1000's of hours with a 60lb metal prop?

rv6ejguy
05-09-2005, 12:03 PM
I'm gald others are finding this thread so entertaining.

Well RCS is a 2 mile road course built in 1987, Has left and right corners, Has hosted Formula Atlantic, ARS, Players GM Camaro series, Honda Michelin series, Canon/ Yokohama FF 1600 series, and the Yokohama/ BFG/ Reiniking GT/ MP series. It's not oval racing. There was always a big East/West rivalry so the comments that you mention don't surprise me. Mosport is a great track, certainly better than RCS but this is where we race. I'm not towing 2500 miles to go the Mosport. Since Westwood closed over 15 years ago in Vancouver, RCS is the best we have in Western Canada.

You might want to check the HIGH standards that aircraft machine work is done to. "The Aviation Consumer" magazine, July '99 reported "spotty" quality control on valvetrain parts, mostly on valve seats and guides. Apparently in their testing, TAC's A&P found 60% of the heads examined were outside manufacturers specs and many of these were OEM new or remans! Problems included non-concentric valve seats, improper seat widths and excess guide to stem clearance. Any automotive shop machinist understands the importance of a properly performed valve job for engine life and performance. Again, the question begs to be asked, what are you getting for all of this money?

After having customers complain for years about problems with their TCM engines, Beechcraft (Raytheon) has compelled TCM to produce "special improved" engines for installation in their airframes. Customer complaints included excessive vibration, camshaft and cylinder corrosion, low compression and high oil consumption. Let's remember that these are brand new, certified aircraft engines worth in excess of $30,000 each.

TCM's standard and "improved" tolerances for balancing parts are as follows: Crankshafts, counterweights and gears- 21 and 12 grams respectively, connecting rods- 14 and 2, pistons 14 and 2. Combustion chambers are now balanced within 3ccs vs. 8 on standard engines. Japanese automotive engines routinely come from the factory with all of these tolerances under 2 grams and race prepared engines usually have this reduced to under 0.5 grams as weight imbalances have long been understood to reduce life and increase vibration. Chambers are usually die cast or fully machined to less than 0.5 ccs in volume difference between chambers. TCM has implemented many other changes to make the performance and reliability satisfactory which is absolutely routine in the automotive world. I find TCM's standard specs appalling.

Not sure what you are getting at here about metal props. Egg designs the whole package and knows a lot more about this than you do. He has these recommendations because it works. Egg does not allow metal props because 1, the C of G would be way outside the forward limit, 2, he can't afford any more weight, 3, the harmonics are outside the envelope of the redrive and damping system to deal with 4, a variable pitch prop is required with auto engines to achieve proper performance over a wider rpm range, this means electrically adjustable as there is no provision for hydraulics through most of the redrives available which precludes using a Hartzell.

Rotax publishes maximum prop weights and moments of inertia to be used on their engines as well so ensure safety within the limitations of the redrive bearings, gears, case and damping system. The highly developed and tested Powersport Wankel redrives also have specific recommendations on propellers to be used. This is basic engineering. The Marcotte's like I use have no prop weight limitations and have the ability to use a hydraulic prop if desired, however many combinations have not been tested. This is a very important aspect of redrives. If you are a student of history, look at what P&W and Wright went through on developing damping systems for their radial engines. You don't recommend something which may lead to a failure.

I've refuted all your points with facts. Your unsubstantiated treatise does not hold much water and you are exactly what I referred to earlier as an "armchair expert" on this subject. You have not responded that you either are a professional, experienced engine builder or have even flown in an auto conversion aircraft apparently but are attacking what you have no first hand knowledge or experience in.

Jconard
05-09-2005, 06:05 PM
My earlier point on the cranks was precisely that the egg setup lacked the beef to handle the harmonics of a big metal prop. A lyc crank will do this. You now agree as does Egg, that at least those dynamics, common to aircraft, are beyond the envelope of the egg/sube design. I assume you agree that the crank would be equally insufficient in a direct drive scenario.

This I pointed out earlier based on my experience with VW conversion which can only use a wooden prop, even when, as I pointed out earlier, they are fitted with SCAT cranks (solid chromoly forgings). You now agree.

You also agree that all of those conversions are equally unable to tolerate the harmonics and weight of a metal prop. Again my earlier point about crank size was exactly that point.

Allow me to offer a quote from an erlier post:

"The aircraft crank is beefy to handle resonance and gyroscopic loads from the prop. Remembber that a prop is a 60 lb pair of flywheel arms that are constantly accelerating and decelerating. This adds torsional stress and harmonics that an auto crank is not able to handle. This is why the VW conversions, even with chromoly scat cranks, (far stronger than a sube crank, often used in alcohol midgets), still can only use a lightweight wooden prop."

You also already agreed with the slower, heavier, and thirstier issue, but offered smoothness and simplicity as compensating.

As to my personal experience, as a driver and team owner I bought and raced professionally built formula cars engines, including as high as the atlantics. I helped friends build japanese drag race engines, and am familiar with the 20R, 24 R, and 4AGE engines as well as the early inline 6's from Datsun. When I was younger I built dozens of porsche club engines, and VW aircooled engines for off road racing or drag racing. Built Type 1, Type 4, Porsche type 4 and 911 engines. As an aside, very few shops in north america, for cars have the ability to grind even a 911 crank.

I have been a part of countless dyno and track test sessions...although as time wore on more of the wrench work was done by others.

You throw out alot of anecdotes about spotty TCM quality, but never circle back to a few facts: A lycoming will run for 2000 hours, and a specific efficiency you admit you cannot achieve, and do it with less fuel and less weight, and fewer systems.

Assume for a minute that I am an ignorant armchair guy. Teach my why I should disregard the following engineering maxims:

1. Simple is preferred to complex
2. Probability of failure increases at the square of complexity.

Please also tell me, as you haven't, why the complexity of engine management is necessay in a fixed rpm, almost unvariable rpm scenario. If you answer that question, pplease do so in a way that accounts for the lower actual efficiency that seems to be achieved by these systems in the world?

While we are on it, you also have not given a reason to prefer a system which constantly circulates high volumes of fuel, at high pressure, through the cockpit and back to the tank. You mght say vapor lock...but the only RV I know of to go down on a flight from Vapor lock was a sube.

The applications are so different it seems that all the "experience" you claim to have is taking you in directions that are simply unwise in an airplane. Tht is why I will not fly one.

rv6ejguy
05-10-2005, 12:04 AM
I'm afraid your logic escapes me on the propeller, bearing thing here. These are in fact auto engines, not originally designed to power an aircraft. I think most people understand that. The redrive is required to drive the prop at an efficient rpm while allowing the engine to produce its rated hp at roughly double the prop rpm. The redrive also handles the thrust and gyroscopic loads. Direct drive auto engines don't exhibit a suitable power to weight ratio in most applications. Its just the nature of the beast.

I think you will find that most auto conversions use a composite prop for the reasons previously listed. Is there some reason why you would want to use a metal prop specifically against the recomendations of the powerplant manufacturer. I don't understand.

I think the previous posts list the advantages and disadvantages of the auto vs. Lyc and why dozens of people are choosing auto conversions despite some disadvantages. No point to rehash this.

Sorry, not familiar with a 24R engine. Toyota never offered such an engine in North America. I think you mean 22R which powered trucks and Celicas for many years.

We now match the SFC of the O-360 at .42 lbs./ hp/ hr. Weight is and always will be higher with an EJ22T than an O-360. No dispute there.

A Lyc CAN go 2000 hours between major overhauls but they don't always. Many require top end work long before this, especially if flown infrequently. The Sube and Wankels typically need no work done internally for at least 1000 hours and we are heading towards the same 2000 hour TBO with many engines here. You don't have the oil consumption, valve adjustments, sticky valves, head and jug issues that sometimes show up on certified engines.

The post where you mention the Sube crank quality is not mine. The EJ22T crank is forged alloy steel and heat treated from the factory. Likely better quality than the SCAT forging. We see NO failures on Sube cranks. Not ever even turbocharged at very high outputs. Rods are forged alloy steel as well, again NO failures. Unlike some Lyc cranks I might mention.

Sube engines all come with EFI and direct fire ignition. These are proven to be more reliable than carbs and magnetos because they have less moving parts. Apply your own law here. No rotor, no points, no shaft or gear drive, no venturi to ice up, no float arm to break, no needle and seat to stick. MTBF of the OE ECU is in the millions of hours. I've worked on EFI engines for many years and see lots of German and Japanese vehicles with the original everything in them over 20 years. Pump, injectors, sensors and unfortunately even fuel filters which people neglect to change. Not only that, since there is almost nothing moving, there is virtually no maintenace. Emissions dictate EFI for their intended mission.

Would you actually take the factory developed EMS off one of these engines and stick on twin mags and a carb? This would be undoing millions of dollars worth of engineering, development and testing to make it less reliable. I don't understand!

You have fuel in an RV, right between the pilots even with a Lyc. If the fuel valve breaks on a line ruptures, you will have a cockpit full of fuel and no way to stop it. EFI requires high pressure pumps. No way around that.

Vapor lock on the one Egg plane resulted in a recomendation to use 100LL above 12,000 feet I think plus a redesign of the pump/line layout and heat shielding I believe. Someone with an Egg can correct me here if I'm wrong. Remember we are still on a learning curve here.

Like I said, fly your Lyc and enjoy it. The others who want a Sube or Wankel will hopefully be happy. Different strokes for diffrent folks.

thallock
05-10-2005, 01:16 PM
This is an interesting thread, but has started to degrade somewhat, as would be expected with the subject matter. It is pretty apparent, that this is a deeply divided issue, and one side is not likely to sway the other side much at all.

The original premise was that if you plan on using an auto conversion in your RV, then you should expect to be a test pilot. Well, I cannot agree more. Of course, with any homebuilt aircraft, you can expect to be a test pilot no matter what engine you put in it. That's why the FAA makes us fly solo for 25-40 hours. I know, I know, that's not the real issue. The real issue is that with an auto conversion your're going to be more of a test pilot, and for a longer period of time. Well, maybe yes, maybe no.

As far as I can tell, there really aren't that many all-in-one FWF packages available for RVs. You know, the package that you just bolt on to the front of the airplane and fly. With all of the different variations and options with Lycomming and Lyclones, just placing the order is an ordeal. No, the only all-in-one package that I know of is the Eggenfellner. Probably, the most complete package that you can get. Proven? Well, we won't know until enough people give Jan their money, and fly around for awhile. Until then, people will continue to try and make their own decision look right by jumping on every single glitch in the Eggenfellner package, and any other auto conversion out there.

I would contend that we are all test pilots. If you don't want to be a test pilot, then you probably shouldn't be building an airplane.

BTW, I'm not going to use the Eggenfellner conversion--too expensive. I really do want to be a test pilot, so I am putting together a rotary conversion. Thanks George.

Cheers,
Tracy.

RudiGreyling
05-11-2005, 01:35 AM
This is an interesting thread, but has started to degrade somewhat, as would be expected with the subject matter...
Tracy.
Ditto, Tracy, I have been following and learning a lot, but the last couple of posts degraded a bit. I still like the thread, and think it is valuable to newbies.

So Please let us get it back on track, let us talk subject and not person!:D

Another interesting picture to BREAK the TENSION:
http://www.bath.ac.uk/%7Eccsshb/12cyl/
http://www.bath.ac.uk/%7Eccsshb/12cyl/rta96c_cyldeck.jpg

rv6ejguy
05-11-2005, 10:50 AM
Love these photos of these HUGE engines. Amazing!

Mel
05-11-2005, 01:05 PM
If your put an engine like this in your RV, you will definately have to move the battery aft for cg...waaay aft!
Mel...DAR

ship
05-11-2005, 02:54 PM
doesn't look like the technology has changed a whole lot in 75 years. can't resist stirring the pot :D

not sure my torque wrench can handle those head bolts...

EridanMan
05-23-2005, 05:32 AM
Hey Guys... Great thread (hooked another newbie)...

I have a feeling this website is going to end up being very bad for my pocketbook/spare time... (I've been thinking about starting a build and I'm doing a bit of research)...

Anyways... I am a bit of an engineer, and I have to say when I heard about putting a Wenkel into an airplane, a little Bell went off in my head...

I agree with what most of you say - when it comes down to it, lycomings are over-engineered in all of the places Airplane's need to be... They're simple, reasonably light, and probably the best bet...

Except... the Wenkel has never really made a good car engine, but there is no doubt that it is an amazing peice of engineering. I can't help but think that, fundamentally, its about as close as you can get to a 'perfect' aviation engine.

A- Lightweight block, small displacement, the Wenkel block is actually significantly lighter than a lycoming flat four... yes, you do need the support equipment, but perhaps a purpose-built aviation wenkel could solve this by integrating a cooling pump and other support equipment into the block.
B- Tiny cross section, great for aerodynamics.
C- No vibration, easy on the airframe
D- ****-near Zero inertial stress... theoretically Wenkels should be about as reliable as a turbine, if engineered well.
E- Failure mode... Reciprocating engines Cease when there is a critical failure... rotaries just tend to loose power/efficiancy, there are no masses to 'lock' the engine... this is true even in catastrophic overheats.

I guess what I'm saying is... i've heard a great deal of discussion about the flat subie engines... but not so much about Rotaries... Theoretically, they seem to be a great idea... How are they working out in practice?

Anyone here fly a rotary?

(I saw the powersport comparison post, but I couldn't find a source article)

Thanks for the great post, i'm going to crawl back into the woodwork and read now:)

-Scott

rv8ch
05-23-2005, 06:01 AM
I guess what I'm saying is... i've heard a great deal of discussion about the flat subie engines... but not so much about Rotaries... Theoretically, they seem to be a great idea... How are they working out in practice?
I guess this thread is getting too long. Rotaries have been discussed, and there are a couple of solutions.

http://www.rotaryaviation.com/

http://www.mistral-engines.com/

One thing I think you will find causing many people to look very closely at the Subaru is that there are three companies competing for the firewall forward RV market. I've got the Eggenfellner (http://www.eggenfellneraircraft.com/) package for my RV8.

EridanMan
05-23-2005, 01:21 PM
I'm sorry, I had read through the thread (granted at 3 in the morning), but I had only noticed a passing mention of rotaries...

I guess I'm just surprised that the Subie Boxer is considered the more 'common' alternative engine (don't get me wrong, I have a huge amount of respect for them... mostly from challenging STi's at the autoX course;)), the rotary just seemed more 'aviation' to me...

I'll do some more searching of archives here to answer my question...

thanks for the thread, in any case:)
-Scott

cobra
05-23-2005, 01:40 PM
Just a note of concurrence- I also feel the Wankel is a far better design for aircraft than old fashioned air-cooled reciprocating monoliths :) . The only downside involves quick emergency reapirs at an airport, IF they ever break (unikely occurrance, that is why I like them).

Upside: excellent power to weight, cheap to purchase and rebuild, very smooth running, low internal part stress, reasonable fuel usage, small shape, uncommon.

Downside: uncommon, parts difficult to find, noisy- best muffled with a turbocharger. :D

ship
05-23-2005, 03:00 PM
Except... the Wenkel has never really made a good car engine, but there is no doubt that it is an amazing peice of engineering.-Scott

isn't this a curious contradiction?

why didn't they didn't make good car engines?

what makes them better for planes if they didn't succeed in cars?

interesting article in previous RVator re the rotary flyoff at Van's....notice the fuel comsumpion of the rotaries compared to the lycomings.....like 40% worse. ouch.

cobra
05-23-2005, 04:40 PM
Im no expert on the rotary design and I have not formed a bias for any specific motor design yet, but here are some possible answers to your questions:

why didn't they didn't make good car engines?

Same logic- why don't Lycomings/Continentals make good car engines, or possibly closer to the argument, why don't turbines/jet engines make good car engines. What difference does it make- we are not talking about flying automobiles.

Actually, I believe the real reason is twofold- 1.) the Wankels are only offered in one sport car model, and it has never been particularly available- low production numbers normally mean higher comparative costs in the auto world, and price rules the mass manufacturers decisions, and 2.) there are any number of other production engines in the automotive world that produce as good or better torque numbers at lower rpm.

Also, the Wankel design was introduced during the oil shortages of the late 70's, which didn't help. It runs more like a 2-cycle than a 4, and it will burn more fuel than a 4cycle equavalent if compared by displacement (not power output). The HP comparison should be with a small v-8, not a 4 cyl econobox. Recent updates to ports/seals/timing/electronics have helped the fuel burn rates and performance from early designs.

To be fair, the Wankel engines are very popular with enthusiasts who race and know how to run them- huge HP available and very reliable as far as race engines go.


what makes them better for planes if they didn't succeed in cars?

Light weight with excellent weight to power ratio; water cooling allows tight tolerences and long life; smooth running; best when running at high rpms for long periods of time (cars spend most of their time at 2000-2500 rpm, not 4500-5000 rpm). These engines really only have 1 moving major part like a jet engine, and it acts more like a gear than a piston/rods/valve train.

As to the high fuel consumption- the burn rates are actually very similiar depending on how the tests are structured and how the fuel systems are set up. You need a set amount of fuel to produce power (approx 0.5gph/hp) , and you need to provide a rich fuel to air ratio to keep the head temperatures low, more so with air cooling.

The numbers Ive seen suggest ~5.5 gph at cruise for a 200 HP engine. Either engine can be leaned for cruise but not for high power production- the difference is that the Lycomings/Conts need to be leaned manually (inaccurately?). The Mazda has fuel injection/ computer engine management available to set timing, fuel ratio, and altitude compensation. The Mazda also should not overheat as easily as a leaned out, air-cooled engine might.

The rotary certinly is not the only good aircraft engine design option, but it is probably better (IMHO) than any recropocating design and is a viable, cheap subsitute for high durability, lower-powered applications than the current turbine/jet engine market makes available to us.

EridanMan
05-23-2005, 06:18 PM
cobra... you hit basically everything.

The only other thing to add is failure mode...

Nothing short of complete fuel starvation (or total electrical failure) will cause a wenkel to completely die... overheat the engine, and your seals will break down as you gradually lose power... loose lubrication? same deal... I've read reports online (in the past week) of Flying Wenkels loosing their cooling systems, only to make it all the way home by running the engine right up at his thermal redline for almost an hour with no danger of it seizing on him (granted, I wouldn't want to have had to be the one to rebuild it afterwards).

gmcjetpilot
05-24-2005, 04:16 PM
The rotary certainly is not the only good aircraft engine design option, but it is probably better (IMHO) than any recpocating design and is a viable, cheap subsitute for high durability, lower-powered applications than the current turbine/jet engine market makes available to us.Rotary engines are great but noise, fuel consumption and installed weight are not the pros and never will be, no matter how cool they are. Recent heads up flight test with two rotary powered RV-8s against Van's demo 180HP RV-8 says it all. Rotaries burned more fuel, are louder and weigh more (ref. Van's RVator).

Comparing weight you have to go by installed weight, not the weight of a stripped down short block.

Performance: Finally at least the rotary had equal performance to the Lyc/Hartzell RV. T

Cost: The Rotary engines were custom installations, cowls and cost more than an O-360/Harzell combo. Not sure if a homegrown Mazda B13 would have as high as performance as the custom modified powersport rotary engines. A Hartzell prop is about 5 grand. The MT electric C/S props on the rotary engine RV's are about 10 Grand! :eek:

Water-cooling is great if the aircraft is designed for it with fuselage or wing mounted heat exchangers like a P-51. Till now most water-cooled auto engines have setups that look like an after though or a work-around to adapt to the original air-cooled installation design. Oh, yes, water-cooling weighs more and is more complex.

Look, all the talk in the world will not override numbers and actual side-by-side comparisons. For the same performance, with more noise, fuel and weight and complexity does not sound like a leap forward, just different. As I have said, if you want to go flying, put a Lycoming in. If you want to tinker, invent and experiment (a lot), put in an auto conversion.

Cheers George

cobra
05-24-2005, 06:21 PM
Good points, possibly valid, but hardly conclusive with only 4 units compared with so many configurations possible. I have not read the RVator article, so I cannot comment on it- is it available somewhere? All I can say is that your summary contradicts other comparison reports, so there should be reasons for discrepencies.

The Rotaries can be noisy for sure, but the jury is still out on how best to muffle a rotary motor without degrading performance. The air cooled motors are loud too when short pipes are used.

The weight issue is subjective- it really depends on how the motors are set up, how they are cooled, what batteries/generators used, etc. From what Ive seen, the weight issue is pretty much a draw (can be slightly heavier or lighter).

Questions concerning the test setup::
Which generation motors were used (there are at least 3 of them available from Mazda, each better than the last)? Were the 300-400 HP rotaries ignored for comparisons or just the early models that produce around 160 HP in stock form? Were turbocharged rotaries included (they are significantly quieter than straight pipes and obviously produce more power). Rotaries love turbocharging to improve mediocre air scavenging tendencies when normally aspirated.

If you want to compare fuel burn rates, make sure the comparison is fair- (include temperature parameters, same power levels, etc). Id like to see how the Rotary fuel systems were set up- carburated or fuel injected, how/when were they each tuned prior to the test, and what were the test parameters (was one type favored, biased test structure)... those kind of variables.

I do agree however, that a head to head test is a very good way to compare as long as the tests are unbiased. As a minimum, this test compared a very mature design with one still in early development, so the conclusion is not surprising.

"As I have said, if you want to go flying, put a Lycoming in. If you want to tinker, invent and experiment (a lot), put in an auto conversion." That statement makes about as much sense as saying air cooled engines have killed more pilots than other aircraft engines- probably true, and misleading.

My attitude is simply, if it works, chose the best alternative based on durabilty, performance, and cost in that approximate order. My best guess is that a rotary will outlive any reciprocating air cooled engine of equal power output, several times over at a fraction the cost- because they have far less mechanical internal stresses and they are manufactured in commercial aquantities to keep costs in check. BTW, if it were not for tinkerers, we would still be walking everywhere, living in caves, and cooking around campfires. :eek: Technology evolution is desirable and inevidible.

leeschaumberg
05-24-2005, 07:58 PM
A good modern, efficient, and powerful aircraft engine in the size needed does not exist today. Many people say this and say that, but the former holds true. A person that claims fuel consumption at cruise means nothing to me. Fuel consumption is determined by pounds of fuel burned and the horsepower produced. (BSFC) This corrects horse power and fuel consumption to a standard temperature.
A good fuel for tomorrow does not use any thing made from anciently decomposed plant and animal matter. Oil made from newly grown plants and hydrogen. With these two we can run and fuel every thing in use today. The octane and cetane of these two is very good.The aircraft engine of tommorow will not use spark plugs.
With the millions of people working in the oil business and the trillions of dollars in the oil business it will take a while to change.
Lee

gmcjetpilot
05-25-2005, 12:00 AM
Cobra:
I think the rotary in the 150-200hp range is one of the better alternative engine choices. Even the Subies with turbo charges have shown that they have acceptable operations. All these engines are not quantum leaps but simply an adapting an internal combustion engine, with all the same limits imposed by the laws of physics a Lycoming has. Unless it is going to be really lighter, faster, more economical, easier to install and maintain, for me, the old fashion way (Lycoming) is still the only choice for me.


I agree with you 100%, the tinker and inventor are the ones that make the way. Orville and Wilbur Wright where homebuilders, right. ;) The "adaptation" of auto engines auto engines and water-cooling was done over 70 years ago with the Pietenpol Aircamper in the 1930's, with a Ford model-A engine.

To over come the big disadvantage of a Lyc, I bought a good core cheap (got lucky) and overhauled it myself (total cost for O-360, $10,000). To keep maintenance down I operate with the limitations and fly often (dis-use is the killer of engines). As far as fuel burn I can throttle back and poke around at 160 MPH instead of 195MPH on less than 7 gph. Plus I get to use a cheaper Hartzell (hydraulic) vs the more expensive electric props with their maintenance disadvantages. It would be nice if the inventors would make a reduction unit for a Rotary engine with a hydraulic c/s prop set-up.


Cheers George

cobra
05-25-2005, 01:49 AM
GMC
It is the laws of physics that give the rotaries a big advantage. A lot of energy is wasted speeding up and stopping heavy pistons, rods, crankshafts, camshafts, valves, rocker arms, etc twice during each revolution of the motor. That energy pounds bearings, produces heat and friction, and generates vibrations that fatigue metal, break parts and shorten engine life. The loose "stacked" tolerances required in an air cooled motor only make the wear and vibrations worse.

The rotary operates more like a turbine than other motors- the pistons/rotor rotates in a continual radial motion, no slapping valves or camshaft drive losses, high rpms available if desired, near-continual and smooth power push vs power pulses pounding each head and crank bearings every second revolution.

Orville and Wilbur were bikebuilders. One of their biggest (most important) inventions was the light-weight motor they made to power their aircraft; funny noone mentions that fact.

Your point about hydraulic c/s props is a biggie in favor of Lycs. Im thinking that I'll compensate to some extent by using either a cruise or 3-bladed propeller on a turbocharged and ported second gen motor (w 240 HP on tap) for climb/takeoffs. The high rpm capability and extra torque should help to some extent (6000 rpm available without adding undue stresses).

EridanMan
05-25-2005, 01:15 PM
Just make sure we deliniate here between 'practical' and 'theoretical' ideal engines...

Currently, the best, easiest, simplest and probably fastest solution out there for builders who wanna 'go now' is going to be a lyc... simple as that. They're proven, they work, they work well, and god knows they've got a pretty good 50 year track record.

But... That doesn't made them the ideal aircraft engine... They might be the ideal 'right now' solution, but their design is _far_ from perfect. They are, fundamentally, a 50 year old 'patch' do a design (flat-4 reciprocating) that is fundamentally bad at producing full power for long streaches of time.

I'm reaching back here (so if I'm off, don't sue me;)), but IRC, a reciprocating engine's internal stresses scale exponentially with the preassure on the pistons (power produced)... this is exascerbated by the high-torque, long through nature of a Lyc... Lyc has counteracted for this by creating an engine that has reinforcement in all the right places... but the engine runs under such high stresses that it requires constant oil changes, constant lubrication (running), and it produces several very undesirable side effects (vibration, huge frontal area)...

I guess I've noticed a kinda Lyc 'religion' on here, where because its been around for 50 years, obviously its perfect... this is, of course, ludicrous... Lyc engines are like Porsche 911 race-cars... Bad ideas that have been brilliantly implemented so that they work well...

Yes, they work great... yes, they're going to work quickly, easily, and reliably, and yes everyone will fix one... They're probably the optimal solution at the moment... But to say that the aircooled, long throw horizontally opposed air-cooled engine configuration is somehow the end-all and be-all ideal for aircraft propulsion is... well, kinda ludicrous.

I think the biggest problem is just that the GA market is so small, its not worth the investment for most companies to put any time, energy and effort into developing for it (especially since it sat stagnat for 30 years)... Lets home Experimental's succeed in breathing some life back into it.

All Cobra and I were saying (I believe, don't mean to speak for you, Cobra) is that, on a theoretical level, the Wenkel configuration is a far more 'ideal' solution than the long-throw horizontally opposed engine... It is just fundamentally more suited for light-weight, highpower for extended periods of time. Am I necessarily talking a B13 or B20 conversion? not at all (although rotaryaviations planes are reasonably impressive, and I know I read one guy who had a flying Mazda engine for a 5200 dollar total investment (salvaged/rebuilt block and turbo)... not bad for a 180hp engine... But, probably requiring a **** of a lot more specialty rotary expertise than I have.

I (like the rest of us, I'm sure) will be watching the aviation powerplant market very closely over the next 5 years... It'll be interesting to see where the very-small-turbines end up... On a theoretical level, a Turbine is just about perfect for an aviation application... the question will be can they keep manufacturing costs and fuel-usage low... On the other hand, a Wankel offers 80% of the advantages of a Turbine, with far lower production tolerances needed (no need to spin at 61k rpm), and theoretically less fuel use needed as well. perhaps it's a better comprimise?

Modern short-throw auto-engines (with reduction gear) is another decent solution, the trick is keeping the power-to-weight and complexity issues under control... (as well as making sure they're ready to operate at 95% for 6 hours at a time)... I'm not holding my breath there, but it wouldn't be the first time I was wrong.

I guess all I'm saying is... Lycs are a great choice... they're going to run, they're going to be relatively easy to install, and they're going to be reasonably fuel efficiant and easy to service. If I was putting an engine into my plane next week, Its probably the best choice...

But... I'm not... and Lyc's are far from perfect... So I'm going to wait and see if anything more interesting comes down the pipes...

Simple as that;)

gmcjetpilot
05-25-2005, 01:53 PM
GMC
It is the laws of physics that give the rotaries a big advantage.Again in theory it is great, but the proof is in the pudding (or is it the dismembered finger in the chili?) A rotary is still squeezing gas/air together and burning it. I don't see a big advantage, only differnt. Anyone who is interested in rotary engines should read everything they can. Tracy Crook of (RWS) Real World Solutions is a straight shooter and shares the pros and cons in a straightforward way, with out too much hyperbole. The cons of the rotary are well documented by RWS. One is gas mileage. I talked to a RX8 car driver at the gas station and he said it was great, but......... it gets horrible gas mileage and has no low-end torque. It has a listed 18/24 MPG city/hwy mileage , but is is closer to 15/21 MPG, real world.:eek:

Tracy addresses fuel burn and the noise problem. My feeling is all these cons are OK, even the higher installed weight is OK, if it provided clear performance advantages (read speed, climb...). At this time they do not, but they are getting better. We shall see; may be the new RX8 renesis engine will be a rocket in planes? it does have better performance will it be enough to outweigh the down sides. And oh yes, LYCOMING RULES :D

Regards George

RVbySDI
05-25-2005, 03:13 PM
I have read with great interest this entire thread from beginning to end. F1Rocket, Tom Maxwell, Cobra, Gmcjetpilot I agree with all of you. Now that I have said that I hope everyone recognizes that each one of these distinquised gentleman represent different sides of this debate. There are several issues being discussed here not the least of which is the question of which engine to put into my RV9A project.

Here are my thoughts on this debate as I have on occasion discussed them with anyone who is within earshot of me and willing to listen. I personally agree with leeschaumberg's comments stating that:

A good modern, efficient, and powerful aircraft engine in the size needed does not exist today.

Let me preface anything I say from here on out with this statement. I am not an engineer, heck, I am not even a mechanic, I am just your average airplane manufacturer (after all that is how the FAA sees me when I register my homebuilt RV) out there trying to build the best airplane that I can so I can enjoy the pleasures in life I have chosen for myself to enjoy.

If you want to really look at alternative engines for aircraft there are others that no one in this thread has examined. I have talked with and read articles from knowledgable individuals who say that the real issue with producing power for an aircraft has to always revolve around the amount of torque that any engine can produce. It is the torque that allows for the ability for speed, climb, cruise, everything that we want an aircraft to do (at least in the prop world, I am not a jet jockey so this could be totally different for you turbine heads out there). Well, if you want torque, and lots of it, the ideal motor is going to be an electric one. Electric motors generate darn near 100% of its energy into torque. imagine the climb characteristics of an electric motor in your aircraft.

Of course the all important problem with electric motors is feeding it all of that electricity to generate that torque. Well, I would say that the true experimental aircraft builder out there who wants to look at alternative engines should be examining the hydrogen fuel cell industry. To me that is the future of propulsion whether it be ground based or airborn in orientation.

The Subies and the Wankels are still trying to tap into the same 70+ year technology that the Lycons are doing. The only true difference I am seeing between any of the "aircraft" engines and the "auto-conversion" enginees is in the secondary systems (i.e. ignition, cooling, mixture, transmission of power to the driving force, etc.). Ok, I know there are all of these debates that discuss the beefiness of what in the auto world can be called a big block 4 cyl Lycon to a small block Subie or Wankel. The reality is that whatever house you choose to reside in these are still the same old technologies that Orville & Wilbur, RollsRoyce, Henry Ford, Mercedes or countless of the other engine forefathers of the internal combustion world devised a century ago.

There have been increases in the capabilities (metalurgy comes to mind) to creat blocks of metal that can surround and control an extremely violent explosion countless thousands of times per minute that are much better than those gentlemen could do "way back then". However you look at it though, there really isn't much difference in the design.

Outside the above discussion however, this debate over Lycon's versus autoconversions really is a matter of economics. The reason I am examining the potential of the autoconversion is the fact that I wanted an economical engine to place in my RV that would give me the performance I want. However, the real truth of the matter is I am having a very hard time chinking down 25K plus into an engine. With that idea in mind I cannot understand why a new autoconversion engine package is coming out to be equal or more in price to a Lycon package. Afterall, that is the only real reason that I am willing to turn away from the tried and true proven "technology" of the Lycons. Now, I recognize that I could go out there and purchase an auto engine myself and configure it to operate in my airplane for cheaper than the 25K plus I would pay to some of these out their selling the "plug and play" packages. Truthfully though, I can do that with a Lycon for much less than the price of a new Lycon engine also and with a lot less trouble for my efforts.

I suspect that the motivation driving those choosing Lycon packages over autoconversions is the same motivation driving me to lean that way now too. As much as I like the Eggenfelner Subaru package, and I really do like it a great deal, the reality is that I can't really afford it any more than I can afford a brand new Lycoming Mattatuck clone IO-320 with FADEC installed and constant speed prop out in front. So, I will most likely end up finding a low or mid time Lycoming engine as inexpensively as possible to put into my RV. Perhaps I will have to rebuild it to meet my requirments. If so, since I am not a mechanic, I sure bet I will learn a lot about how these massive blocks of metal make airplanes fly.

Well for what it is worth there is my .02 on the subject. As I am just beginning my research on this engine issue I welcome any and all comments concerning my input. I honestly greatly appreciate all who have contributed to this thread. It makes for very interesting reading.

RVBYSDI
Steve Ingraham
Will be adopted by an RV9A
project on 06/02/05

cobra
05-25-2005, 03:34 PM
George,
Im playing devils advocate here- the Lyc is the engine of choice for the masses, and that is fine with me as long as they are all satisifed.

You pretty much verified the points I was trying to make concerning rotary performance. First, 21 mpg is not bad for a 200 HP engine- compare that mileage to any small v-8. My Mustang Cobra (5.0 liter, 240HP stock) regularly gives 18-22 mpg depending on how it is driven. The RX7 mileage is only bad when compared to lower output engines, not when performance is similiar. The low-rpm torque deficit is a complaint of all small displacement motors- they just have to be driven differently than a musclecar to reach their potential.

Your lyc would have terrible mileage and worse performance in a car, because its top end rpm is severely limited by a long stroke. It would have to run at full throttle most of the time, at least until it melts down. It would be fine in a tractor however .

Theory vs practical application: The 13B rotary has abt 80 cu in displacement; Im guessing your Lyc is 360 cu in?? Same power output, same fuel burn rate. You have to rebuild every 1000 hrs, right? Tracy's Mazda shows no wear at over 2000 hrs so far. I (and others) have repetedly said that fuel burn rates are mostly a function of HP produced- the engine simply converts chemical BTUs into kinetic energy, no magic extra power involved.

The RVator article aside, Tracy reports that his lightly modified 13B (1989 model) generates 185 HP, drives his RV-4 abt 220 mph, gets 6.0 gph at cruise (170 mph) and 8.2 gph at 202 mph, TBO is 2000 hrs so far and counting (costs only $600 for a full rebuild), and his is a little lighter, but not significantly so, than a Lyc. Im pretty sure he uses a fixed prop too, but I could be wrong there.

The basic, first generation rotary is a close replacement for the much more expensive Lycoming- same weight, same performance, same fuel use, better reliability, lower initial and rebuild costs over its lifetime. The only argument I see FOR a Lyc is that everyone else has one and it is a little easier install. Remember, my criteria is durability/reliability, performance, then cost.

FWIW, Id probably pick a Subaru over a Lyc as well, because they run so much smoother and cost less over their lifetime as well. I feel the Rotary is the best option of the three, but a small cheap turbine engine would force me to reconsider.

cobra
05-25-2005, 03:59 PM
Steve,
It is easier to generate big torque numbers by running high rpms through a transmission.

Do you have any idea how big and heavy the DC motor would have to be? How about the weight of batteries and high amperage cables? Whatever power source is selected in the future, it will have to be light-weight and probably environmentally clean.

Commercial fuel cells are probably at least 5-10 years into the future, and they still require a carbon source to fuel them, probably natural gas, which in turn, requires a strong (heavy?), high-pressure tank. A fuel cell powerful enough to power an aircraft would have to be huge and expensive to generate the amperage needed.

As long as we are talking future hopes, why not a helium or hot air filled vessel with nuclear-heated steam jet propulsion? :)

RVbySDI
05-25-2005, 04:25 PM
Do you have any idea how big and heavy the DC motor would have to be? How about the weight of batteries and high amperage cables? Whatever power source is selected in the future, it will have to be light-weight and probably environmentally clean.

Commercial fuel cells are probably at least 5-10 years into the future, and they still require a carbon source to fuel them, probably natural gas, which in turn, requires a strong (heavy?), high-pressure tank. A fuel cell powerful enough to power an aircraft would have to be huge and expensive to generate the amperage needed.

Ok, first things first. I couldn't tell you specific numbers on the weight of a DC or an AC electric motor but I do know that a 20 hp electric motor generates more torque than a 150 hp internal combustion engine could ever dream of. Plus it is instantaneous tourque. The second the electricity is put to the motor it is generating 100% of its capable torque. That 20 hp electric motor is going to weigh somewhere in the neighborhood of 50 to 100 lbs. What does that 150 hp internal combustion engine with all of its necessary secondary components weigh?

Second, the hydrogen fuel cell does not require batteries. The fuel cell converts electron flow to usable electricity as the chemical reaction of the fuel cell strips hydroden atoms off of the "carbon source" fuel and those hydrogen electrons flow through a membrane. In fact, if science can overcome some obstacles, the ultimate fuel would be H20. Good 'ol water has the necessary energy stored in it to generate the electricity. And the last time I looked water weighs less than gasoline whether MOGAS or 100LL.

Now, third, you tell me. What is cleaner? Burning fossil fuels in an internal combustion engine or a chemical reaction with H2O that generates electricity as electrons flow from one side of a membrane to another and leaves left over hydrogen and oxygen atoms as waste?

Lastly, the hydrogen fuel cell definetly does not have to be huge and expensive. It is huge and expensive now for the same reason Lycoming engines are huge and expensive now. Both scientist(s) and aircraft companies (Lycoming, Continental, etc.) currently are attempting to recover any R&D and/or liability costs as quickly and as easily as possible.

RVBYSDI
Steve

gmcjetpilot
05-25-2005, 05:00 PM
Quote: Cobra "Id probably pick a Subaru over a Lyc as well, because they run so much smoother and cost less over their lifetime too. I feel the Rotary is the best option of the three, but a small cheap turbine engine would force me to reconsider."

Tracy Crook competed in the 2004 Sun ?N Fun 100. He ran in the 160hp category and came in 3rd.

The 2004 Sun 'N Fun 100 Race, had (4) categories: Generic +300hp, 180hp and 160hp classes and one 180hp RV category. Tracy flying in the 160 HP category came in third, at a very respectful 189.172 knots. He claims his engine puts out 185hp? Why race in the 160hp class? Is that all the rotary can do, 160hp? Why not run in the generic-180hp or 180hp-RV classes?

In the 180 HP RV class the winner (Lyc) came in at 204.254 knots. The top 5 finishers all came in above Tracy's 189.172 knots. In the generic 180hp class the top 6 finishers came in between 228 to 193 knots. Note: SNF 100 absolute times are known to be a little inflated due to the fact the race is not a true 100 miles as I have been told, ref. Van's RVator article a few years ago. http://www.aircraftspruce.com/sunfunraceresults1.php

Yes I agree the Lycoming is easier to install, and the installation time Tracy has spent "experimenting" on his RV-4 rotary engine, is probably approaching the time to build a whole RV. Nothing wrong with that but lets get real.

Tracy has tweaked the **** out of his plane and he is still off the pace, and my hat is off to him. I admire his work. Granted the other RV's airframe may be a little more elegant and have less drag, but that is the point. Most alternative engine installations have high cooling drag, despite the superior water-cooling. Certainly this is an area that needs more work in the alternative engine world. I am watching with interest.

Lycoming is a specific built, low rpm, high torque air-cooled purpose built aircraft engine, designed to be light and directly drive a propeller, fixed or hydraulic constant speed. I will be the next to install an alternative engine when Van's aircraft has a flight test of an alternative engine RV that cost the same or less than 180hp Lyc RV while giving better performance and economy or when the RV's with alternative engines start winning races. They are just not quite there yet. Also a hydraulic prop control would be nice in the reduction drive for these alternative engines.

Whether it is a Rotary, Subie or an engine yet invented, I am waiting with interest. For now a new Lycoming will provide the average RV pilot with more than 13 years of reliable service (from 60 years of statistics) without an overhaul. My old Apache had 160hp 2200 hour O-320's and good compression and low oil use, but than it was flown almost daily. It was still going strong when I sold it.

All the claims of better service and economy with an alternative engine is conjecture at this time. I'll get back you when I can point to a RV that has flown with a rotary for +2000 hours, +13 years, with no modification and only routine service. All tinker time must be recorded. Most of these planes are worked on more than flown, my be just for fun. Alternative engines are tinker heaven. Not that there is anything wrong with that. You want to fly, Lycoming. A new O-360 cost $18,000 and can be installed with "off the shelf" stuff with no modification. You want to tinker, put something else in. Oh yea, did I say LYCOMING RULES. :D (Nuff said it has been fun)

Cheers George

PS: "Small cheap turbine" is an oxymoron. For general (private) aviation in small aircraft, they are too expensive and likely always will be, when weighted against the number of hours of utilization, the flight "mission" and the mis-match of airframe and engine performance. If you need 500-6500hp engine, fly +800 hours a year, turbine yes, if you have $$$$$$.

Michael White
05-25-2005, 06:14 PM
And the last time I looked water weighs less than gasoline whether MOGAS or 100LL.

RVBYSDI
SteveSteve,
Not true. H2O is 8 lbs./gal.; Gasoline is 6 lbs./gal. This is why the sump drain in your airplane is at the lowest point when the airplane is at rest.

Interesting facts about fuel cells, though. I hope they get them R&D'ed soon. Would be an interesting way to power an aircraft.

Best,

ship
05-26-2005, 01:10 AM
since this thread is already in the weeds, let's have some fun with fuel cells:

there are already fuel-cell aircraft in the air...low-power, high-altitude solar/fuel-cell platforms that can loiter for months. :cool:

H20 doesn't contain "energy" in the conventional sense (we'll skip the quantum physics), i.e. water is not a fuel (unfortunately!).

Fuel cells require hydrogen and oxygen, which requires a LOT of electricity to "crack" H20 into 'H' and '0'.

Since H20 is among the most inert substances known, it requires (absorbs) large amounts of energy to break it apart.

the reverse is also true, i.e. H and O are among the most reactive of all elements (which is why both are not found in pure form in nature). allowing H and O to combine releases a large amount of energy in the form of heat.

the world's biggest fuel-cell vehicle is the space shuttle. that big tank is nothing but liquid H and O stored in separate tanks. the fire lights when the valves are opened. no spark necessary.

trivia: the fuel pumps on EACH shuttle engine could fit under the cowl of an RV yet they generate 70,000 hp. (it's no typo: seventy thousand) pumping 30,000 gallons per MINUTE :eek: ...or slightly higher than a rotary :D

most of our electricity comes from fossil fuels, so when you take into account the whole energy loop, fuel cells in cars are roughly the same total pollution as normal cars.

in the ULTIMATE 'hollywood' irony, the only "clean" fuel cells are those made from water "cracked" by electricity from nuclear power plants. :D

RVbySDI
05-26-2005, 08:36 AM
I enjoy these conversation as I am always learning. My point for bringing up the discussion on Hydrogen fuel cells is that there are other alternative engines out there that may ultimately prove to be the best choice for producing thrust in our toys. The real change comes when someone thinks outside the box. The auto conversion people are attempting to do just that. Lycoming engines are definetly a proven commodity in the engine realm that is hard to beat when you look at overall cost and long term use. On the other hand as many in this thread have stated, if your goal is to experiment with your "experimental aircraft" and enjoy the tinkering process then the auto conversions may be a good alternative choice.

If anyone here is willing to admit the facts of the matter, the truth is that when we make a decision about the particulars of one engine type over another we are really looking at it in terms of the perspective that we choose to see it in. Lycomings rule! Subies rule! Wankels rule! Hydrogen rules! Well it all depends on the particular perspective one is looking at things. That is the way all our choices in life are decided upon. After all why did you choose an RV over a Glassair? Are RV's "better" than a Glassair? An argument that could go on for ever as I am sure Glassair pilots are just as loyal to their aircraft as anyone. "Better" is a point of perspective that can never have a definitive answer.

Thanks for the teachings. I will continue to be a willing student to all who are in the know. I will read and absorb as much as I can from everyone out there whenever I can.

RVBYSDI
Steve

cobra
05-26-2005, 09:34 AM
Steve-
I have no idea how much DC power will be needed to fly- I do know that powerful dc motors tend to be very heavy and that they generate a lot of heat (and ozone, btw).

Re batteries- it is true that fuel cells do not require batteries to operate, but you do have to store the power when the current is not being used and more importantly, to meet peak loads. A large (heavy) capacitor might work, who knows?

As mentioned, water is heavier than gasoline and diesel (they float on water). Unless you can find a metallic catylist to split apart H-O bonds to free up the hydrogen fuel, it will take too much gross power to be efficient.

A fuel cell is environmentally friendly, but it needs hydrogen atoms to operate. What source do you propose as a hydrogen source? Because hydrogen is difficult to store (requires pressure tanks and is extremely corrosive/reactive), the easiest way to obtain it by oxidizing (burning) a hydrocarbon close to the fuel cell. Natural gas is a clean burning fuel- only water vapor and carbon dioxide are liberated; CO2 is a greenhouse gas however...

"The hydrogen fuel cell definetly does not have to be huge and expensive." My best guess is that it will have to be extremely large to generate sufficient amperage to power an aircraft- that requres a lot of membrane plate area. Most fuel cells now provide only low amperage.

cobra
05-26-2005, 10:03 AM
George-
Didn't Tracy win the 2003 contest at 209 mph? His brochure mentioned a 3rd place finish at 217.5 mph in the 2004 race.

In any case, top speeds are not a particularly good way to compare power output between different aircraft, because so many other variables are involved (aerodynamic efficiency, pilot skill, weight differences, propeller efficiency, etc).

The only way I know of to actually measure HP is on a dynometer, and even there, they generally measure acceleration of a known mass moment to approximate torque, note the rpm, then calculate HP. IMHO, the actual peak ratings used for purposes of race classifications are probably estimated more often than not.

One additional thought: The "tinkering" that Tracy and others have done benefits everyone else thereafter- there is no need to reinvent things already accomplished. To assume that everyone has to go through the same development processes is incorrect, because rotaryaviation and other manufacturers offer the developed products at a reasonable price. The motor is the easy part, the difficulties involved development of the redrive, ECU electronics, and finding lightweight substitute parts where needed. To most of us, the work now only involves assembly.

RVbySDI
05-26-2005, 10:33 AM
Cobra,
I don't know if Hydrogen fuel cells will be a solution in the immediate future or not. What I do think about it is that the potential exist to make it work. Perhaps it will be an alternative. It will take some effort and inginuity by people willing to look at the alternatives to existing technology to do so. The way I look at things is this. I do not want to put aside an idea just because it hasn't been done before. This whole debate over traditional vs alternative powerplants is motivated by those who are always looking to change things for the better and those who are always living by the statement that "If it aint broke don't fix it".

The argument that I see against auto conversion engines stems from the philosophy that: "we have this proven technology (Lycon engines) that is designed specifically for aircraft use that works relatively well. Why would anyone want to do anything differently?" There are a miriad of reasons why I would choose to go with an auto conversion over a Lycoming. There are also a miriad of reasons why I would choose a Lycoming engine over the auto conversion. I need to examine for myself what I feel are the most legitimate reasons for one or the other and go with that decision.

Many people I see building and flying RV's are looking for one thing. Speed! Others, and I would lump myself into this group, are looking at RV's as a relatively inexpensive way to get into a very fast well designed cruiser that is enjoyable to fly. I am not exactly looking to build the fastest drag racer, hotrod Reno winning flyer. Others are building RV's because they enjoy the building process and enjoy tinkering with well proven designs. They are out there wanting to experiment with things to make the plane better, cheaper, faster ("We can rebuild him, we have the technology. . .na. . .na. . .na. . .").

I think the first group of speed merchants would be looking for the high HP output lightweight screaming engines (is that why the Rockets were designed?). The second group is looking for dependable long lasting performance from well proven engines that will not cause them too much headaches or hassles over long years of flying. The last group are the true pioneers who always feel there is a better mouse trap out there. They are going to always be pushing the envelope to find that better design that is going to allow for more. . .(more HP, more speed, more economy, more ???).

Just tell me to "shut up ah-ready" if you are tired of my comments and I will. Whether I continue to contribute or not, I will continue to enjoy the debate.

RVBYSDI
Steve

rv7boy
05-26-2005, 11:35 AM
the world's biggest fuel-cell vehicle is the space shuttle. that big tank is nothing but liquid H and O stored in separate tanks. the fire lights when the valves are opened. no spark necessary.

:D

I really like your contribution to this thread, and I am enjoying reading it. Apparently a lot of others are too, as indicated by the number of viewers. I dislike being an email cop, but for the sake of accuracy, I feel compelled to correct one little bit of your reply. :)

Hydrogen and oxygen are not hypergolic ( no ignition required for combustion). The Main Engines (3 SSME's on the back end of the Orbiter) do consume "vast quantities" of hydrogen and oxygen as you mention, but they do have spark igniters to initiate combustion. There are hypergolic propellants used on the space shuttle for the reaction control systems (RCS) and the APU's providing hydraulic pressure for the Thrust Vector Control systems for both the SRB's and the SSME's. You may have gotten these propellants confused with the SSME propellants.
For the historical record I hope this helps.
Don Hull

ship
05-26-2005, 12:55 PM
Hydrogen and oxygen are not hypergolic ( no ignition required for combustion). The Main Engines (3 SSME's on the back end of the Orbiter) do consume "vast quantities" of hydrogen and oxygen as you mention, but they do have spark igniters to initiate combustion. There are hypergolic propellants used on the space shuttle for the reaction control systems (RCS) and the APU's providing hydraulic pressure for the Thrust Vector Control systems for both the SRB's and the SSME's. You may have gotten these propellants confused with the SSME propellants.
For the historical record I hope this helps.
Don Hull

Thanks for the kind words. You are absolutely correct. I was cross-feeding while editing to keep the post mercifully short. I was thinking about the peroxide in the RCS units. NAStee stuff! The LOX in the mains needs a Champion spark plug to get 'er lit :)

ericwolf
05-26-2005, 01:56 PM
"Ok, first things first. I couldn't tell you specific numbers on the weight of a DC or an AC electric motor but I do know that a 20 hp electric motor generates more torque than a 150 hp internal combustion engine could ever dream of. Plus it is instantaneous tourque. The second the electricity is put to the motor it is generating 100% of its capable torque. That 20 hp electric motor is going to weigh somewhere in the neighborhood of 50 to 100 lbs. What does that 150 hp internal combustion engine with all of its necessary secondary components weigh?"





Since others have already commented that on the weight of water and that water cannont be used as a fuel, I won't get into that. I can't help but comment on the electric motor torque thing. Electric motors generate the most torque at zero speed, which means zero horsepower and can generate large amounts of torque at low speeds, but I think that we need a small physics lesson.

Horsepower, not torque is the number that matters. It's just basic physics. Power is the rate of energy conversion. ANY engine or motor producing 150HP at 2700RPM produces 291.8 ft-lbs. The equation to do this is Power = Torque * Rotational Speed where Power is in Watts, Torque is in N-m and rotational speed is in radians/sec. Since we generally use HP, ft-lbs., & RPM, the equation to use is:
HP = ft-lbs*RPM/5252

A 20HP electric motor will produce 10,504 ft-lbs. of torque at 10RPM (assuming that it produces 20HP at that speed), but it is still only 20HP.

In other words, assuming the same prop efficiencies, you will need a 150HP electric motor to keep up with a 150HP Lycoming.

EridanMan
05-26-2005, 03:02 PM
This board is a lot of fun... thanks guys:)

just another .02 cent post, then I'm going to shut up and read more;)

Just to clarify:
Fuel Cell != Hydrogen engine... The two terms are improperly used as synonyms in the media.

Hydrogen combustion engines (both the shuttle: a rocket, or a conventional IC) operate on the same principle as any other combustion engine, the Main advantage to them is that they emit mainly H20 (although, they can also emit small amounts of HO (Hydrogen monoxide), so they're not completely clean. They also tend to react (combust) extraordinarily quickly, so they're better suited for rocket motors. In all other respects, Hydrodgen is an inferior fuel to Hydrocarbons. It packs a significantly lower energy density (almost 2:1 lower) meaning you need _Far_ more of it (in both volume and weight) for the same punch, is far more difficult to store and it is gaseous at atmospheric preassure (harder to work with).

You'll notice, the only hydrogen-powered rockets are _ENORMOUS_ vehicles... most smaller rockets actually are powered by methanol (a hydrocarbon) or its variants... on a small scale, the higher energy density far outweights the less efficiant (for _rockets_) burn.

But as it happens, slower burn tends to be better for IC's anyways.

So... Hydrogen itself is a pretty suboptimal fuel (especially when you consider it's very difficult to create in quantity).

Now-

fuel-cells are a (relatively) new technology. Both combustion engines and fuel cells capture the exothermal energy from a fast oxidizing chemical reaction. Combustion engines, however, are by definition extraordinarily thermodynamically innefficiant. Remember what I said about energy density? Well, a good combustion engine is capturing maybe, at _BEST_, 15% (haven't read the number in a few years, I think I'm being optimistic) of the available energy from reaction. The remaining 80-85 is lost to heat, noise and other undesirables.

Fuel cells, on the other hand, catalyze the exact same chemical reaction as combustion, but they do it in a very controlled environment where they can actually extract the exothermic electrons from the reaction and convert them straight into electric current. The advantage? a Thermodynamic efficiancy in the 50-80%... some of the most efficiant chemical processes known to man... Theoretically, fuel-cells converting fuel into energy at the same rate as a combusion engine will produce 4-8 TIMES the usable energy from the same amount of fuel consumed. Now, this energy is electric, not kinetic... so figure another 50% hit from the electric system and motor innefficiancies, but you're still looking at 2-4 times better efficiancy (more usable energy per fuel) than even the best combusion engines. Now go back to what I said about Hydrogen - it has half the energy density of Hydrocarbons... therefore the 'green' reason for a 'hydrogen fuel cell', is theoretically, you could get the same usable energy out of the same quanity of fuel as we're used to dealing with today... What the media doesn't tell you, is that if you ran a hydrocarbon through those same fuel cells (well, the catalysts have to be different for the different fuels), you would get twice the energy from _that_, ie, 2-4 times the range on the same time, and you wouldn't have to deal with the hugely inefficiant process of creating the hydrogen in the first place (a hydrogen based economy will only exist if we somehow find a vast, limitless supply of electrical energy such as space-based solar or fusion... barring that, creating the hydrogen with modern generating technology creates _FAR_ more pollution than burning the equivolent hydrocarbons... I hate to say it, but its true).

But, I digress.

The other rub the Fuel cells (and why they're taking so long) - note in my above caveat, I say that "If you're reacting fuel at the same rate as a combustion engine...", well, we're not yet. In fact, so far we're _far_ from it. Now - the added thermodynamic efficiancy means you don't nead to react as much fuel to get the same energy of course, but current fuel cell car's require multiple large and heavy fuel cells in produce enough current to provide for fairly mediocre automotive performance. Now, there's no reason why this won't change, and god knows, a bunch of people a **** of a lot smarter than me are spending a lot of time working on it... But until fuel cell weights and rates get a _LOT_ better than they are now, you won't be seeing them in a plane any time soon. (we're probably 10-15 years before they're suitable for cars, give or take... give it another 10 or so before they are light enough for planes? I dunno... I pulled those numbers straight out of my rear... but don't hold your breath;))

RVbySDI
05-26-2005, 03:40 PM
Let me preface anything I say from here on out with this statement. I am not an engineer, heck, I am not even a mechanic, I am just your average airplane manufacturer (after all that is how the FAA sees me when I register my homebuilt RV) out there trying to build the best airplane that I can so I can enjoy the pleasures in life I have chosen for myself to enjoy

Thanks to everyone who has set this po' boy straight concerning the skinny on all of this high tech mechanical/scientific stuff. I definetly will be the first to say that I am not the smartest kid on the block. . . wait I did say something like that in my first posting (yeah that was my quote above). I am on this website to learn as much as I can so I am glad you guys are here. My comments about hydrogen fuel cells and electric motors were to open the debate to include true alternative powerplants. I for one am unwilling to accept the fact that internal combustion engines that were created over a century ago are the ultimate answer to powerplant capabilities.

This thread seems to have started with the discussion of traditional aircraft powerplants vs alternative (auto conversion) powerplants and everyone seemed to be sticking with their own perception of what they thought were the "best" for our RV's. I hope my posting on fuel cells has not detered others from continueing with that original intent of this thread.

RVBYSDI
Steve

ship
05-26-2005, 07:44 PM
I hope my posting on fuel cells has not detered others from continueing with that original intent of this thread.



Actually, I think we have a classic in the making. I don't know about anyone else, but IMHO this thread is just STARTING to get interesting. THIS is what 'experimental' is all about :D , i.e. educational as per FAA Part 'whatever' that oulines the nebulous 51% rule.

Just look at the "views" on this thread.....higher ratings than American Idol

The ultimate beauty of it is there's no "right" answer....never will be.

I actually make a point to check this thread religiously. As far as I'm concerned, we've got a TERRIFIC virtual hanger with a bunch of liars sitting around telling tall tales willing to learn a thing or two from each other. Now all we need are some virtual beers... :D

PS: fuel cells (and hydrogen engines) ...and electric cars...have been around as long as the IC engine.

PSS: there's a nuke powered airplane ...flew long ago. There truly is nothing new....so far. Practical? that's another story.

KEEP THOSE LETTERS COMING !!!

ship
05-26-2005, 10:36 PM
SCENIC DETOUR

hypergolic
exothermic
thermodynamic efficiency
energy density
catalyze

uh oh..I can hear some eyes glazing over. we're getting into deeper waters with some of these technical terms.

in the spirit of keeping this thread educational and fun, let's define them in laymen's terms so we don't leave anyone feeling left out when they crop up in the engine discussions (remember them??):

**disclaimer** chem was my WORST subject in engineering school but I somehow aced physics and thermodynamics. don't ask me how.

HYPERGOLIC = combustion without external ignition source
-- certain chemicals, when mixed, will ignite explosively without provocation
-- my first marriage

EXOTHERMIC = any chemical reaction that gives off heat
-- your 5-year-old lights the living room carpet on fire
-- the average mother-in-law
-- tabasco sauce (not really exothermic but you get the idea)
-- all internal combustion engines utilize exothermic reactions

freebie:
the opposite of exo- is ENDOthermic = any reaction that removes heat or needs heat
-- welding
-- the average marriage
-- evaporation
-- baking cookies

THERMODYNAMIC EFFICIENCY = warning: don't spring this one at the cocktail party unless you KNOW there's nobody in the room who knows what you're talking about!!! :D
-- here's the "money" line for impressing your date = "the percentage of "E=MC squared" that ACTUALLY gets converted into work (kinetic, mechanical, moving) energy via heat transfer"....hooyah!!
-- when the schlub next to you asks what that means, you rattle off: "how much of the fuel's mass gets converted into heat gets converted into pressure which gets converted into moving that piston down or turning the turbine wheel which is measured as horsepower"
-- when they melt and ask for your autograph, you say in a suave, cool voice of confidence: "the percentage of the heat that is converted into horsepower. a 100% therm. efficient IC engine would be silent, cold with no exhaust"
-- leave the party NOW!! while you're still in the smoke screen.

freebie:
this is not to be confused (as it usually is) with mechanical efficiency, i.e. friction losses, etc. which actually GENERATE heat :eek:....

"but you just said that heat= power? so an engine can create it's own power?" NOPE!!

clear as mud, right??

ENERGY DENSITY = horsepower per unit of weight or volume of fuel
-- how many hot dogs per gallon of propane in the grill as compared to burning a gallon of 100LL OR a gallon of hydrogen in the 'ole Weber

-- (yes yes I know it's BTU not horsepower per unit but it's easier to take the short cut for the sake of explanation )

CATALYZE/CATALYST = a substance that initiates or accelerates a chemical reaction without itself being affected
-- the chemical version of your basic spark plug
-- the average mother-in-law


WHEW!....i'm tired of reading this myself....back to our regularly scheduled program

Dave Hertner
05-29-2005, 09:33 PM
Hello everyone,

I too have been following this thread with great interest. It is interesting to hear the many ways that people have tried to raise the efficiency of the Otto cycle piston engine over the years. We all seem to tackle the problems of inefficiency by looking to different fuels and by porting the heads.

Hydrogen has been hearalded as the panacea for years and we have spent billions in research trying to make a square peg fit into a round hole. I have heard the truth about hydrogen only once in all of my research into alternative fuels and engines. It is that there are only two ways to make enough of it to make a difference. Large scale nuclear and even larger scale wind. Both will take a catastrophe before being implemented.

Engineers use ?well-to-wheel? analysis to determine which engine option has the most promise. This accounting approach considers the energy consumed in the following processes: extracting the raw energy source (e.g., crude oil, natural gas), transporting the raw energy source to a refinery, refining the raw energy source, transporting the refined energy source to the consumer, transforming the refined energy source into vehicle motion.

The well-to-wheel analysis uses three energy sources: petroleum, natural gas, and renewables/electricity. The most desirable systems require the least amount of energy to move a vehicle 1 mile. The following key describes each approach:

Gasoline ICE: Gasoline-powered internal combustion engine (Otto cycle)
Diesel ICE: Diesel-powered internal combustion engine (Diesel cycle)
Gasoline Fuel Cell HEV: Fuel cell hybrid electric vehicle with gasoline reformer
Diesel ICE HEV: Diesel-powered internal combustion engine, hybrid-electric vehicle
Naphtha Fuel Cell HEV: Fuel cell hybrid electric vehicle with naphtha reformer
FT Diesel ICE: Fisher Tropsch diesel-powered internal combustion engine
CNG ICE: Compressed natural gas, internal combustion engine
FT Naphtha FC HEV: Fisher Tropsch naphtha, fuel cell hybrid electric vehicle
Liquid H2 FC HEV: Liquid hydrogen fuel cell hybrid electric vehicle
Methanol Fuel Cell HEV: Methanol fuel cell hybrid electric vehicle
Gaseous H2 FC HEV: Gaseous hydrogen fuel cell hybrid electric vehicle
E-85 ICE: 85% ethanol/15% gasoline internal combustion engine
Electrolysis GH2 HEV: Electrolysis-produced gaseous hydrogen hybrid electric vehicle
Ethanol Fuel Cell HEV: Ethanol fuel cell hybrid electric vehicle

The results of this study showed that the most efficient systems they examined are the fuel cell hybrid electric vehicles, followed closely by diesel hybrid electric systems.

The most efficient system considered (fuel cell hybrid electric vehicle) is only about 20% more efficient than a conventional diesel engine and about 35% more efficient than a conventional gasoline engine. Considering their great cost and complexity, these conventional approaches hardly seem worth the trouble.

So we need to stop deluding ourselves in thinking that we are going to get anywhere with these collective efforts in raising efficiency. We need to come up with a different type of engine that will deliver:

High efficiency (44%-64%)
Low Pollution
Low Cost
Low Maintenance
Long Life
High Power Density
Negligible Vibration
and Multi-fuel Capability

This seems like a lofty list dreamt up by some pilot who lost touch with reality! To obtain an efficiency of 60% one would have to design an engine that would HALF the fuel consumption of established engines.

There are 2 patented engines out there that can put a check mark beside every one of the deliverables listed above. They are truly revolutionary. (please excuse the pun) The problem with the current engine manufacturing establishment be it automotive or aerospace is that of inertia. The established engine manufacturers have millions, if not billions invested in producing the Otto cycle engine. This type of engine has become the standard and they will fight to protect their investment. You have all heard the story of the little guy who invents a carb that returns 80mpg. He takes it to the establishment and they promptly buy him out. At all costs!!

I put out a feeler the other day to a forum that I belong to. One that listed the hypothetical engine characteristics of these two engines. I then asked a simple question. "What would a company have to demonstrate to you with regard to the hypothetical engine before you would be comfortable buying one?" The responces were varied and I think that a few people thought I was off my nut!!

I was pleased to receive a number of responces from people who truly believe that we are still innovators and inventors. We are going to be flying 100 years from now burning fuel that we grow in a sustainable way using engine technology developed today wondering why there were so many of the flying establishment resistant to change.

Let's all open our minds to the possibility that we can convert more than 30% of the btus in gasoline to work done. Let's shoot for an engine that will approach 70% efficiency and put one in an airplane and as one respondent suggested "...fly it across the Atlantic..." just to thumb our nose at the establishment!!

Dave Hertner
Effectus AeroProducts Inc.

rv8ch
05-30-2005, 05:00 AM
Let's all open our minds to the possibility that we can convert more than 30% of the btus in gasoline to work done. Let's shoot for an engine that will approach 70% efficiency and put one in an airplane and as one respondent suggested "...fly it across the Atlantic..." just to thumb our nose at the establishment!!
Dave, It sounds like you have information on this engine, and you want to get it developed. If the designs are patented, then there should not be a problem telling us the details. Most of the responses to your earlier post were what I would call healthy skepticism.

When electronic ignitions came out for aircraft engines, 99% of the people spent a lot of time telling us how horrible and dangerous they were. Today, they are accepted as "good things". The same will happen with your proposed engine once people see it working. It's as simple as that.

I stand by my earlier comments to your original post. If you can develop such an engine, I would not waste time on the aviation business - the market is too small. I, for one, would love to hear more details.

ship
05-30-2005, 07:19 PM
To obtain an efficiency of 60% one would have to design an engine that would HALF the fuel consumption of established engines.

...or double the amount of work extracted for same fuel.


There are 2 patented engines out there that can put a check mark beside every one of the deliverables listed above. They are truly revolutionary.
since they're patented: what are they? Fisher Tropsch? what fuel types?

Dave Hertner
05-30-2005, 08:35 PM
Ship and Mickey,

Have a look at www.starrotor.com and www.quasiturbine.com and let me know what you think.

Dave

mlw450802
05-30-2005, 08:57 PM
Just so we are truly all on the same page when talking about increasing the efficiency of a heat engine.
Some french guy named Carnot, showed the maximum thermodynamic efficiency possible in a heat engine operating between two heat reservoirs could be described as the (Tmax-Tmin)/Tmax.

If we look at the peak combustion temp in the engine as being around 5000 R and the exhaust at around 2000 R, then the max possible thermo efficiency is 60%. This accounts for no frictional losses and other heat losses. The actual
carnot cycle is purely theoretical and an internal combustion engine is pretty far removed from that.
While the actual thermo efficiency of a well tuned otto cycle engine is probably 30% or less, the ability to double that in the real world is unlikely. The Carnot efficiency is like the speed of light; you can't exceed it for a HEAT engine.

ship
05-31-2005, 10:14 AM
Ship and Mickey,

Have a look at www.starrotor.com and www.quasiturbine.com and let me know what you think.

Dave
Interesting stuff, but the plot in Quasi website says it all: gasoline and diesel piston engines are STILL the most efficient converters of BTU to work after 100 years (nuke doesn't count for this exercise).

I had a long-winded response outlining the shortcomings of both, but I decided it was better to spare the forum from any more torture.

cobra
05-31-2005, 12:11 PM
It is probably possible to improve the efficiency of any internal combustion engine simply by letting it run hotter- it just will not last very long without lubrication and will blow itself up from detonation. Cooling is not compatible with high-efficiency because it compromises btu's generated from fuel oxidation. Everything is a compromise; most of us prefer an engine that runs reliably with as much durabiltiy as we can get.

Id guess the most efficient motor is probably electric and/or ion drive, but only under cryogenic conditions with superconducting magnets and windings- hardly practical in a small aircraft.

btw- I found the quasi-rotary engine quite interesting. partiucularly that it was designed to run in the detonation mode. Compared to the Mazda, it looks (to me) like it would have big problems with hot spots, durability, and carbonizing with its rollers completely exposed to combustion heat and fuel mixture. Eventually, it would lose compression and fail as the "parallegramed levers" freeze- it therefore looses the real advantages of the rotary design (simplicity, reliability, durability).

If I understand the first example, it looks like a normal jet engine with an external combustion chamber between the compresser and turbine (I dont see any advantage there).

ship
05-31-2005, 02:04 PM
Starrotor's main design feature violates the intake heat paradox of heat engines, i.e. adding more heat to the intake charge will lower the power density.

Quasiturbine is more realistic in theory, but it appears to be a modified Wankel despite the rhetoric to the contrary. I would expect similar "negatives" as Wankel: Low compression, poor low-end torque; poor fuel efficiency & emissions problems. The "flexing" rotor is worrisome. And there's no clear way to transmit power out of the engine.

The "detonation" theory is poorly articulated on the Quasi site. The discussion fails to account for the VERY scary dynamics of shock waves, i.e. reflection, interference, wavefront compression, etc. etc.

Detonation engines have historically done just that: detonate.

In pure 'work' terms, the most efficient engine system is still -- drum roll please -- the closed-loop steam turbine. Stick a nuke in the burner, add secondary recovery and you've got the holy grail (so far). Staggering power out of mere kilograms of fuel with no combustion byproduct, almost zero friction loss and low heat loss with regenerative recovery systems. See "Navy".

Not exactly practical for everyday use in planes ...but it HAS been done :)

cobra
05-31-2005, 02:24 PM
I agree Ship,

Detonation has a nasty habit of reforming metal (into missiles?). ;) I should add that pressure and heat cause detonation.

The downsides you mentioned with Wankels are partly overcome by turbocharging (lower noise output, increases the "implied" compression ratio, better low end torque, better effiiciency, better forced airflow) but it still has some issues with leakage between the exhaust and intake cycles that hurts emissions.

Good call on the efficiency of the nuc steam engine. Doesn't the Navy still use generators and electric motors between the engine and propeller?

kcameron
05-31-2005, 04:43 PM
Ship, you're correct to dismiss the starroter and quasiturbine as revolutionary new engine technologies. Their claims are typical pie-in-the-sky bulls**t one hears reads about untested "new" ideas. All upside and no discussion of the disadvantages. As cobra pointed out, they are similar in many respects to existing technologies and suffer from additional drawbacks.

However, on one point, I must disagree with your assessment. The starroter's heat recovery mechanism is a reasonably good idea. Note that the exhaust heat exchanger is inserted downstream of the compressor and upstream of the combustor. In this position, it heats up the compressed inlet air in the same manner as the combustor. A well-designed exchanger in this position could make a significant improvement to the overall efficiency. It wouldn't make up for the design's mechanical problems or the low pressure ratio (6:1). The same idea could be applied to a gas turbine engine. In fact, I bet it's been tried but the high air flow rates of a turbine probably make it impractical.

My 2 cents.

Kev

ship
05-31-2005, 05:07 PM
the exhaust heat exchanger is inserted ... upstream of the combustor.
Kev

you're right...I didn't look closely enough and assumed fuel was being introduced earlier. The low p.r. would make preheat more effective vs. high p.r. engines.

either way, the concept is d.o.a.

parashak
05-31-2005, 05:30 PM
Steve-
I have no idea how much DC power will be needed to fly- I do know that powerful dc motors tend to be very heavy and that they generate a lot of heat (and ozone, btw)....

A fuel cell is environmentally friendly, but it needs hydrogen atoms to operate. What source do you propose as a hydrogen source? Because hydrogen is difficult to store (requires pressure tanks and is extremely corrosive/reactive), the easiest way to obtain it by oxidizing (burning) a hydrocarbon close to the fuel cell....

My best guess is that it will have to be extremely large to generate sufficient amperage to power an aircraft- that requres a lot of membrane plate area. Most fuel cells now provide only low amperage.

This discussion prodded my memory. I was at Oshkosh 2003, and saw an electric plane (trucked in from Worcester, MA). I haven't heard much from them since.

A non-profit associated with Worcester Polytechnic (FASTec) was trying to adapt a fuel cell to a Dynaero Lafayette III modified glider. They were supposed to be starting with a 25kW cell and moving up to 75kW for a 2004 race sponsored by Boeing. No word on if the project got off the ground. Pun intended.

Aviation Today article (http://www.aviationtoday.com/cgi/av/show_mag.cgi?pub=av&mon=0102&file=0102ednote.htm)
WPI article (http://www.wpi.edu/News/Transformations/2002Fall/onawing.html)
Aviation Now article (http://www.aviationnow.com/content/ncof/ncf_n46.htm)

Regards, Paul

parashak
05-31-2005, 05:52 PM
Good call on the efficiency of the nuc steam engine. Doesn't the Navy still use generators and electric motors between the engine and propeller?

Steam plant efficiencies (thermal) are on the order of ~30-33%. Lot's of heat rejected to seawater. The Navy currently uses steam turbines attached to to propeller via a reduction gear system. It also uses steam driven generators for electrical loads on the ship. By the way, the Navy is researching a way to use an electric propulsion system on all its future vessels. CHINFO website (http://www.chinfo.navy.mil/navpalib/cno/n87/usw/issue_9/power_system.html)

As far as nuclear powered aircraft, it has been tried, believe it or not. I spent 6 months up at Idaho Nuclear Engineering Lab during navy nuc training and saw the carcass of the project failure on site.

AirAttack.com article (http://www.air-attack.com/page.php?pid=18) INEL site info (http://www.inel.gov/facilities/tan.shtml) radiationworks.com site (http://www.radiationworks.com/flyingreactor.htm)

ship
05-31-2005, 06:04 PM
Doesn't the Navy still use generators and electric motors between the engine and propeller?

in newest subs, yes. steam turbines drive gens. near-total heat capture & regen. cryogenics. exotic alloys for corrosion control. very compact. ultra slick. obviously money is no object.

nuke surface ships use direct-turbine shaft propellers (geared). electric pods have proven troublesome so far on massive cruise&cargo ships. might see them on next-gen stealth ships.