RV-7 Egg H-6

[rv6ejguy]

Originally Posted by Jconard

YOU CANNOT SAY THAT THE CONTEST WAS EVER ABSOLUTE POWER OR SPEED AT ANY FUEL FLOW.

If it really was, in your mind just absolute output and top speed at any airflow, why compare the 6 cylinder subes against four cylinder lycs...why not eight cylinder lycomings, etc...??? What possible use could the top output or speed at any fuel flow have to an airplane conversion.

But you are correct that an engine is at its top volumetric efficiency AT ITS TORQUE PEAK. This is a point that the aircraft engine crowd has been making for years now as a suggestion that for speed per unit of fuel, a gear drive high HP engine is INHERENTLY LESS EFFICIENT.

This is why a direct drive engine operating in cruise at its TORQUE peak is the most efficient way to convert fuel into force. It seems you now agree. And I am glad we all finally agree that endlessly spining a small engine for HP, and above torque peak, will always generate power at a higher cost in fuel....duh!

The rest of it result from what to do once the fuel becomes force, and then weight and drag are important, again it is an airplane specific application.

Which gets us all back to the original question all along: If it truly were better in an airplane environment to have small displacement, high reving engines which are water cooled, do you think it would be done????

Or is it more likely that the reason aircraft engines are light weight, direct drive, large displacement engines is because that is the simplest way to get enough power, at the torque peak, to run the engine most efficiently, and hence deliver the best thrust per unit of fuel?

Actually, I believe the comment was that NO Subaru would ever match a Lycoming in speed. A silly comment since it is obvious that several Subaru engines put out more than 180hp stock. I'd venture that a properly prepped turbo EG33 would make more power, longer than even a turbocharged 720 Lycoming.

I think realistic comparisons at least for RVs comes down to engines with similar fuel flow, power and weight to the standard O-360.

I think you miss the point about the whole discussion. It is not what is better as there are winners and losers in that discussion, it is that fact that hundreds of people obviously don't think that the Lycoming is the wonder engine that many here think it is. It does have issues and problems and disadvantages in real life. Eggenfellner would not be in business otherwise and 700-800 gyros would not have Subaru power. People are looking for an engine which is smooth, cheap to operate, cheap to overhaul, reliable and fuel efficient. The Sube seems to fit the bill for many. it is an ALTERNATIVE to the Lycoming. It does not beat it in every category.

Actually I don't agree with your assessment of fuel flow vs. engine speed on geared engines. This does not happen at torque peak, it happens where the point of max VE and lowest frictional losses merge, typically about 400-500 rpm below torque peak. I have never been an advocate of heavily cammed atmo engines spinning way up there to make power for aircraft use, exactly why my engines are both turboed and I raced turbocharged cars very successfully for many years.

I do agree that having to spin a geared atmo engine well above torque peak to make competitive power is a losing situation with regards to SFCs.

Finally, Rotax shows that a well designed, high revving, geared, liquid/ air cooled engine is far lighter and gives better SFCs than a direct drive, air cooled engine. This is a purpose designed engine which is not the same as an auto engine like the Subaru which is bound to be heavier.

People are seduced by the cheap, reliable, mass produced Subaru longblock. It is the total package that can use more refinement, study and testing to improve power, fuel flow and weight. The Egg packages are not optimal today but fit many people's needs despite some disadvantages.

If people ignored the marketing and just looked at the facts about Subaru performance to date and applied a bit of logic, it has been pretty clear that measured performance has not been what Subaru converters claim. Conspiracy? No. The facts have been there to see for some time. If you believe stuff like 200 mph Glastars and 50% lower fuel flow and hp claims at 1000 rpm less than stock power peak rpms, you are not using your noggin'. We see lots of this stuff in aviation, no different in the engine conversion world.

You should have read the mud slung back and forth between the Sube converters on E-Subie forum a few years back. It was ugly with lots of personal attacks, finger pointing, the call for dyno tests, fictional hp figures, fictional speeds, on and on. I left after it just got too ridiculous to stand and Jan left to work on his products while the others withered away in red ink and broken promises.

I just question the anger than some people seem to have about auto engines in aircraft and that they believe people are stupid and foolhardy to install them. Why be so angry about it? Fly a Lycoming if that is your desire. I just don't see the opposite side of the coin where Subaru people are saying Lycoming users are a bunch of mindless idiots. This is simply a choice, a choice based on different criteria. I've stated for some considerable time that if your criteria is best speed vs. fuel flow vs. weight, the Lycoming is the clear choice at this time for your RV.

[Yukon]

Ross,

My "anger", if that is even the right word, comes from the deceit and mis-information from the auto conversion world. Ross, you are a beacon of candid, reasonable opinion that can be found NOWHERE else in the conversion world. As you know, nobody will dyno, weights have been hard to get from the converters, performance has been exaggerated, fuel flows have been masked. No Ross, people are not stupid for using conversions, but should do it for the right reasons. As long as performance and efficiency are not important, conversions are a viable choice.

[DGlaeser]

Originally Posted by Yukon

Ross,
My "anger", if that is even the right word, comes from the deceit and mis-information from the auto conversion world. Ross, you are a beacon of candid, reasonable opinion that can be found NOWHERE else in the conversion world. As you know, nobody will dyno, weights have been hard to get from the converters, performance has been exaggerated, fuel flows have been masked. No Ross, people are not stupid for using conversions, but should do it for the right reasons. As long as performance and efficiency are not important, conversions are a viable choice.

Performance, efficiency, and weight are important, but so are other factors, like smoothness, quietness, cabin heat, ability to use auto gas, parts and overhaul costs, and just wanting something different (I am building an Experimental airplane, after all). Each builder gets weed through all the (mis)information and make a choice based on his/her own preferences - thank goodness.

[Rotary10-RV]

Originally Posted by Yukon

Ross,

My "anger", if that is even the right word, comes from the deceit and mis-information from the auto conversion world. Ross, you are a beacon of candid, reasonable opinion that can be found NOWHERE else in the conversion world. As you know, nobody will dyno, weights have been hard to get from the converters, performance has been exaggerated, fuel flows have been masked. No Ross, people are not stupid for using conversions, but should do it for the right reasons. As long as performance and efficiency are not important, conversions are a viable choice.

John,
There are sources of honest information out there. (Like Ross. We need a 20B EMS there buddy!) Sometime they might not post to this forum. I was sold on using the 20B rotary after seeing multiple dyno pulls done by Al Ghisen on the ACRE and Fly Rotary forums. (290 HP at 6800 rpm NA) And sense Al is running the engine on a Velocity I would be supprised to see him on this forum. There are many false sources of information passing themselves off as cannon. When using the net for info you always have to do some dilligence to be sure the people speak the truth, but that isn't really a suprise. Like Ross I simply want honest plain-spoken truth about ANY engine install. Does the baffleing fit from the factory for the Lyc you're putting on, or is it a mess that requires a lot of work before working right? I've got close to 20 years of engine building behind me and as such I can usually spot a faker right away. Many can't though, so we will try to help them if possible. There is nothing wrong with being skeptical, but some people are so set in their ways that they are just naysayers. This does none of us any good.
Bill Jepson
Rotary10-RV

[Yukon]

See Bill, that's what I'm talking about. 290 hp at what SFC???? In a light plane, you can't mention one without the other. 290 hp at 22 gph is of absolutely no practical use to our little airplane. Just like the Innodyn turbine, thirsty powerplants cannot gain popular acceptance in our sport, because there is nowhere to put the gas.

Diesels have the best SFC, but so far are way too heavy for our planes. If someone does manage to install one, it will be at a great useful load penalty.

Of course I realize you and I are just having a casual conversation, but that's just the way the Subaru converters talk. No mention of weight, no talk of SFC, just alot of ......... "AIN"T IT SMOOOTH".

[RV7Guy]

I was in the Alternative camp for a while. Then the experience with Crossflow soured me. After that, I learned that much information on Alternative engines did not exist. This has been hashed over many times regarding weights and performance.

Now some issues that haven't been brought to the front of this debate. There have been many failures and partial failures of Alternative engines causing emergency landings and in some cases off field landings resulting in damage. Interestingly there have been several that have not made it to the Forums or general information sources. Being somewhat skeptical, I suspect the lack of information was to protect this segment of the Experimental world. I could be wrong.

To name a couple, David Dormier had a belt failure. He was open and disclosed fully this experience. I commend him for this action.

One noted Eggy disciple has had at least 2 unplanned landing events. Neither made it to the headlines. (I think there were 3)

One of the Mazda powered planes bit the dust.

I noted that Ross mentioned an off field landing but didn't mention the cause. About the only real reason for an off field landing is that the fan quit turning. Not throwing stones here Ross, only pointing out a fact from your post. You have been very up front on the discussion and it is appreciated.

A Crossflow owner had two drive failures on a Glastar. Fortunately, both were over the airport.

There were a couple of other Crossflow drive failures as well.

There are more but I can't recall them at this time. The point is, the failure or incident rate per hour flown appears to heavily weighted toward the alternative engine.

Now speaking of weight. The AE's are heavier than a Lyc or clone. I don't think this has been disputed. A couple of years ago, I remember somebody posting some stats regarding some tip overs and AE's. There was a rash of them. I wish I could find this information. The computer it was on died a long time ago. I found it interesting especially enlight of the many recent discussions of tip overs of the A models.

Now a few misconceptions and qoute "advantages" the AE crowd like to throw out there.

1) The AE's are smoother. This is true but so what? My ECI IO 360 is equipped with a Whirlwind 200RV propeller. The engine/prop has been dynamically balanced. It is extremely smooth. Nothing has fallen off because of vibration (or any other reason).

2) "I can burn mogas" Again, so what? I've been to dozens of airports over the past couple of years. Only 2 have had auto gas.

3) Fuel efficiency. I noted in recent trip report that I was leaned down to 5.8 gallons per hour at 169 kts of GS. The AE's (Eggys) claim to get similar fuel flow but I have not seen the speed figures. I suspect that you will burn more fuel because you are going slower.

4) Overhaul costs. Lower overhaul costs would favor the AE. We don't really know since there are very few with any significant hours. A clone can be overhauled for a reasonable sum over a factory Lyc.

Furthering this thought, the AE folks will tell you that Lyc's are "old technology." True but they will always be there. The problem with the auto engines is the always changing technology. Look how many evolutions Eggy has went through in their short history. Who knows how long the current H6 will be around. It WILL become obsolete in favor of a newer, better product. How long will it take the parts source to go away. The exception to this is the Big 3 auto engine blocks.

5) Better cooling. Of the few Eggys that are operating in the hotter climates of AZ and CA ALL have signifcant cooling issues especially in climbs. I have some cooling issues in the hot AZ weather with my ECI. I limit my climb rate to whatever I can get with the hottest CHT at 425. In no case has that been less than 500 ft per minute. That day it was 116 when I took off. One local Eggy users says he has to stairstep climbs and is very limited in the hot summer conditions.

I could go on. The bottomline is the hours are just not there yet in the alternative world to consider this a reliable everyday airplane engine. The diehards will posts that there are several with 500+ hours and a couple nearing 1000. Lycs and clones have millions of hours. Sure the Lycs have not been without issue but I would submit the failure ratio is far less for the hours flown.

Auto engines may have a place in aviation but it takes a special person to deal with trials and tribulation to make the work reliably and safely.

Finally, and the question I ask everyone who is pondering an auto engine for their airplane, "Do you feel 100% comfortable flying someone you love behind the engine?" If there is any hesitation, the answer is clearly "NO."

[mgomez]

Originally Posted by rv6ejguy

Most big radials, Merlins, Allisons, PT6s etc. have reduction gears.

Gearbox design is not trivial. Those engines have gearboxes designed by people who know what they're doing, backed up by enormous budgets to pay for design and test.

The market for Subaru conversions or Mazda conversions is much too small to pay for that kind of development.

[Rupester]

I considered an alternative powerplant for awhile ... until I talked at length with CFI friend about engines one day. He told me he has >10,000 hrs in GA aircraft behind nothing but Lyco's and Conti's. He said, "In all 10,000 hrs I have NEVER had an engine quit. I've bent valves where they made awful noises, and I have had 'em stumble and run rough, but I never had one quit on me." Since I'm all about reliability and unforced landings, I made up my mind that day to go with a conventional p'plant ...even if they call 'em Lycosaurus's.

Rupester
RV-9A, QB fuse

[rv6ejguy]

Originally Posted by mgomez

Gearbox design is not trivial. Those engines have gearboxes designed by people who know what they're doing, backed up by enormous budgets to pay for design and test.

The market for Subaru conversions or Mazda conversions is much too small to pay for that kind of development.

Some drives have had torsional testing done like the PowerSport unit however this becomes a massive problem when several different props are being fitted. The RWS units have a unique solution to this You are absolutely correct in saying that this area needs more work in the industry. A good redrive design is paramount for total package reliability. Some drives already have many thousands of hours of flight time now and either never had had any problems or had problems fixed which surfaced. Additional testing on these is a moot point at this time on these ones.

I started work on some accelerometer based vibratory test equipment but had to shelve it for lack of time. The equipment can be purchased commercially for a few thousand dollars these days so it is a smaller deal than it was 10 years ago. The bigger expense is fuel and flying time as only so much can be done on the test stand. All vendors need an RV test mule!

A lot of Cozy Mark IVs are being fitted with Wankels and often turbo ones with pretty good success to date. A lot of this was made possible by drives and EMSs provided by RV guy Tracy Crook.

You might be surprised at the size of this market if you were involved in it like I am. Eggenfellner alone I'd guess is doing over $2M a year. The 2 big Gyro makers, RAF and Groen probably another $2-3M, RAM, RWS, Raven, Marcotte and a host of others including my company probably a couple more mil and there are many other smaller vendors which exist because of the alternative engine market. Figure an easy $10mil just in North America per year. OZ and NZ not to mention Europe account for even more.

I know our aviation sales primarily for AEs has doubled in the last two years.

[rv6ejguy]

Originally Posted by Yukon

Ross,

My "anger", if that is even the right word, comes from the deceit and mis-information from the auto conversion world. Ross, you are a beacon of candid, reasonable opinion that can be found NOWHERE else in the conversion world. As you know, nobody will dyno, weights have been hard to get from the converters, performance has been exaggerated, fuel flows have been masked. No Ross, people are not stupid for using conversions, but should do it for the right reasons. As long as performance and efficiency are not important, conversions are a viable choice.

As I said previously guys, use your brain cells when it comes to manufacturers claims. Would you build a KR2 kit just because people still swear they'll do 200 mph with a 75hp VW up front?

I totally agree with unsubstantiated claims made by all. NSI did "dyno" tests and people foolishly believed them because they were done on a "calibrated" dyno. Sounds impressive. The data was completely ridiculous to anyone who could use a calculator. I exposed this on various forums and FINALLY they admitted problems with their "data". They had to admit that SFCs of .285 for instance were not correct! I got into another quarrel with a nameless Canadian vendor about their claims as well. They threatened to sue me.

My advice is to seek info from actual users about weight, fuel flow and speed before even putting your deposits down. Ask the real questions and if you don't get plausible replies, go elsewhere.