Any current generation subaru FWF's out there

[shogan50]

I'm curious about the current/next generation of Subaru powered aircraft. Not having followed it for a while, it would appear that several Egg... purchasers finally gave up after spending a fortune and got a Lycoming, suffering from reliability and under performance. A few appear to have prevailed after removing a lot of the egg stuff and turbo charging and now play in the same league as Lycoming as far as power and fuel efficiency. One or two, especially 9's, still run original Egg's, . And finally there is Ross, who built his own FFW and at least until his engine got tired was in the same league if slightly lagging (your honest account much appreciated). Are there any current builders looking at Subaru's more or less from scratch?

I know the whole capital E 'Experimental' vs. the plug and play Lycoming argument and don't want to debate that. Just curios if any current builders are planning to go that way. If there are any at KPAE, I'd particularly love to see.

I never did hear what happened to Eggenfelner. It would appear that he closed is doors about 4 years ago, leaving some builders quite unhappy.

 

[txaviator]

I never did hear what happened to Eggenfelner. It would appear that he closed is doors about 4 years ago, leaving some builders quite unhappy.

He's at Viking Aircraft Engines, the Honda engine alternative.

 

[SvingenB]

He's at Viking Aircraft Engines, the Honda engine alternative.

And doing pritty good by the looks of it. The main difference is the Honda engine is fit for the job, a different legue compared with the Subaru.

 

[RV10inOz]

I only know of one successful Subaru install in all of Australia, with lts of doing it right engineering, getting cooling right etc. more HP than most but probably not claimed HP. Pretty quick, but slower than a 180 Lycoming.

Fuel burn is worse. And this guy has all the gear to know what the injectors are squirting.

Fair to say, he would not do it again even if it were free, and he is preparing a FWF for a Lycoming, so here is a good example. The rest not so much.

 

[RV10inOz]

And doing pritty good by the looks of it. The main difference is the Honda engine is fit for the job, a different legue compared with the Subaru.

Are there any gear boxes involved from this mob?

If so

 

[SvingenB]

Are there any gear boxes involved from this mob?

If so

Here: http://www.vikingaircraftengines.com/Photos/Pictures.html

 

[rv6ejguy]

The Subaru engines are just as capable as any Honda engine and FAR more flight proven with something like a half million flight hours to date. There are hundreds of them flying (over 600 delivered) in RAF 2000 gyros and quite a number have over 1000 hours on them now.

The turbocharged STi engines appear to be the way to go for the typical RV3-8. Weight is only slightly higher if done right using the MT composite props, performance is well above the Lycomings and fuel burn is fairly similar. One is currently flying here trouble free and Randy Crothers is about to have his flying again soon after trying the atmo route for a couple years and finding performance lacking. He will have a new STi bottom end with SOHC heads and a new Aerocharger turbo.

Russell Sherwood flies an atmo EG33 powered Glasair in the SARL races and waxed all comers in his class and won it in 2011 I believe. He has been flying for years and has over 450 hours on his.

Keith Spruerer has been flying an atmo EG33 for years in his Cozy, has about 800 hours I believe on it now.

My friend Bill Baxter has about 300 trouble free hours on his EJ22 turbo powered Glastar. Gives really good performance.

Many Egg users have removed their engines and fitted Lycomings after various problems with the EZ30 engines and GEN 3 gearboxes. Others are staying with them through the closed support group Subenews which is of exceptional help technically, dealing with fixes to problems and even working on new gearbox parts and fixes.

Many other Egg users have experienced few if any problems and are happily flying with several hundred hours on them now.

My own plane is all apart now after 9 years and almost 360 hours. I'm making big systems and cooling setup changes and freshening the tired engine. I'll be posting photos and what I have found on a new web page if I ever find the time.

What do we know so far? Seems like universally, these engines don't enjoy a diet of 100LL as it often leads to valve issues. Operated on unleaded mostly, we see excellent life for the most part, many of the gyro engines are going 1500-2000 hours before overhaul and the high time one was over 3800!

Gearboxes and TV are still issues although we have seen reliable results using both the Marcotte and Autoflight PSRUs. I'll be experimenting with flywheel inertia changes on mine when it goes back together. Some Egg Gen 3 gearboxes are working fine, others have suffered multiple problems with bearings, shaft fractures, seal problems and weld breakages. Fixes are in the works for these through the group. One Geared 200Z Sube box suffered an early gear failure which puts into question the reliability of that choice which was an alternative to the Gen 3 boxes (bolt on, no thrustline change). The Ross gearboxes have always had problems but some people know and check them often and they work for them. The GAP boxes have not proven reliable behind the six cylinder engines as Russell discovered- he now uses a Marcotte M300 with no issues.

Done correctly, the Subaru can give good and reliable service as many have proven. Done poorly and you are in for a world of misery and headaches. As I have advised for many years now, Subarus are probably not a good choice for non-gearheads and non-engineers and your average RV builder as there are no fully engineered and tested packages available. Most RV builders are best served by fitting a Lycoming or clone IMO.

 

[SvingenB]

The Honda engine is designed to run continuously at WOT for prolonged time as a an outboard engine for boats. For aero conversion the Honda is perfect. The Subaru is designed for auto use only.

It is therefore much easier to get it right with the Honda than with the Subaru. I'm not saying that Eggenfellner has everything right with his Honda conversion or that using a Subaru is wrong, but I think there is less likelihood of getting it wrong with the Honda because it is initially designed and tested by Honda engineers for a similar purpose. The Honda is also less HP and that simplifies.

Regarding PSRU, the recipe for endless problem free run is found on the Rotax 912. It's called a clutch. Eggenfelner's PSRU looks a bit strange, nothing to save those cogwheels from beating during start and stop and low load running but I guess if enough steel is used, it will hold together for a light prop.

 

[shogan50]

Thanks for the info Ross. I suffer being a former gearhead and current engineer.
I know enough to be dangerous in fluid dynamics and cooling drag and would like to try some things on a sub, but the two obstacles for me are the lead issue and uncertainty doing aerobatics with a turbo. KPEA doesn't, to my knowledge, offer mogas.

 

[shogan50]

The Honda engine is designed to run continuously at WOT for prolonged time as a an outboard engine for boats. For aero conversion the Honda is perfect. The Subaru is designed for auto use only.

It is therefore much easier to get it right with the Honda than with the Subaru. I'm not saying that Eggenfellner has everything right with his Honda conversion or that using a Subaru is wrong, but I think there is less likelihood of getting it wrong with the Honda because it is initially designed and tested by Honda engineers for a similar purpose. The Honda is also less HP and that simplifies.

Perhaps, but there seems to be preponderance of evidence that subaru's hold up just fine, as Ross and others report. I'm not sure I've heard of any core failures - lots of fuel or electron starvation, or gearbox/prop failures.

 

[rv6ejguy]

The Honda engine is designed to run continuously at WOT for prolonged time as a an outboard engine for boats. For aero conversion the Honda is perfect. The Subaru is designed for auto use only.

It is therefore much easier to get it right with the Honda than with the Subaru. I'm not saying that Eggenfellner has everything right with his Honda conversion or that using a Subaru is wrong, but I think there is less likelihood of getting it wrong with the Honda because it is initially designed and tested by Honda engineers for a similar purpose. The Honda is also less HP and that simplifies.

Regarding PSRU, the recipe for endless problem free run is found on the Rotax 912. It's called a clutch. Eggenfelner's PSRU looks a bit strange, nothing to save those cogwheels from beating during start and stop and low load running but I guess if enough steel is used, it will hold together for a light prop.

Incorrect. All auto engines in the last 15+ years are validated for hundreds of hours at WOT and full power by the OEMs before production release. The track record of flying Subarus also proves this. I think 3800 hours in the gyro training environment in a hot climate proves that the engines are very strong.

The Rotax clutch is designed for prop strike protection, it is not active in the TV realm. Sprague clutches have proven to be unreliable as applied to aircraft redrives and other types of clutches like on the ill fated Thielert also have proven unreliable. I personally would not fly with any clutch arrangement which is active during flight operation unless it was well proven with a few thousand flight hours first. There are far better engineering solutions than clutches to cure TV issues.

 

[DanH]

Ross, I have not been following conversion news in recent times. How are the Autoflight boxes doing in service?

 

[SvingenB]

Incorrect. All auto engines in the last 15+ years are validated for hundreds of hours at WOT and full power by the OEMs before production release. The track record of flying Subarus also proves this. I think 3800 hours in the gyro training environment in a hot climate proves that the engines are very strong.

The Rotax clutch is designed for prop strike protection, it is not active in the TV realm. Sprague clutches have proven to be unreliable as applied to aircraft redrives and other types of clutches like on the ill fated Thielert also have proven unreliable. I personally would not fly with any clutch arrangement which is active during flight operation unless it was well proven with a few thousand flight hours first. There are far better engineering solutions than clutches to cure TV issues.

I'm no auto engine engineer (i'm an engineer though, turbines). What we are discussing is reliability, mttf/mtbf. 200-300 hours at WOT for a few test engines is not the same as a TBO of 2000-3000 h or more for a production off the shelf outboard marine engine. It could very well be that the Subaru will hold up just as good in real life (with the proper modifications?), but the Honda is still designed and tested by the factory for this particular purpose, the Subaru is not.

TV is no issue on the Rotax. The clutch is there to protect the gears during start/stop and at no load (zero torque on the propeller) when there is virtually no relative damping. Instead of the gears hitting each other too hard that will possibly cause damage after some time, the clutch sets an upper limit for the instantaneous torque. Indirectly this will also stop TV from developing. The only issue with this setup is the clutch could at least in theory, wear out if you happen to fly often at no torque (rapid descend with low RPM for instance). With this setup the propeller and the engine is decoupled for all practical purposes when the instantaneous load is too high, but still well above the engine torque. Which is exactly what you want.

The alternative is to beef up the gears to increase stiffness and the load the system can withstand without being damaged over time. This will also work, but only if you know exactly what you are doing regarding TV frequencies and stiffness of the total system (engine-gears-propeller). Or you could get lucky, as I think Eggenfelner did by using the 200 HP Subaru reduction drive on the 100 HP Honda.

 

[rv6ejguy]

Ross, I have not been following conversion news in recent times. How are the Autoflight boxes doing in service?

The Autoflight boxes have been good so far in most applications. We saw one failure on a Titan T51 with a very heavy, unapproved prop last year I think it was. The guys using the light props seem to be having good success. These use a Centaflex coupler.

The Marcotte boxes don't break but the rubber bushing couplers don't last forever. Depending on the engine and prop, the lifespan seems to be between 150 and 350 hours. Mine were pretty beat at the 357 hour mark. They cost about $60 to change and a few hours, also easy to inspect. Two users have reported much less severe F1/ F2 with heavier flywheels installed so I'm going that route this time as well. Will be an interesting experiment.

I have no reason to dismantle my gearbox as backlash and bearing smoothness are unchanged from new and it does not make any metal and temps are the same as ever. I will make a small external mod to solve a tiny oil seep from the prop shaft. Can't be sure if the oil is getting by the splines and big nut securing the prop hub or through the C/S set screw plug. I can't remove the plug so it it must be very tight. Since it is NPT, I doubt the leakage is there.

I'll post the a link to the page when I create it showing various worn parts.

 

[rv6ejguy]

I'm no auto engine engineer (i'm an engineer though, turbines). What we are discussing is reliability, mttf/mtbf. 200-300 hours at WOT for a few test engines is not the same as a TBO of 2000-3000 h or more for a production off the shelf outboard marine engine. It could very well be that the Subaru will hold up just as good in real life (with the proper modifications?), but the Honda is still designed and tested by the factory for this particular purpose, the Subaru is not.

TV is no issue on the Rotax. The clutch is there to protect the gears during start/stop and at no load (zero torque on the propeller) when there is virtually no relative damping. Instead of the gears hitting each other too hard that will possibly cause damage after some time, the clutch sets an upper limit for the instantaneous torque. Indirectly this will also stop TV from developing. The only issue with this setup is the clutch could at least in theory, wear out if you happen to fly often at no torque (rapid descend with low RPM for instance). With this setup the propeller and the engine is decoupled for all practical purposes when the instantaneous load is too high, but still well above the engine torque. Which is exactly what you want.

The alternative is to beef up the gears to increase stiffness and the load the system can withstand without being damaged over time. This will also work, but only if you know exactly what you are doing regarding TV frequencies and stiffness of the total system (engine-gears-propeller). Or you could get lucky, as I think Eggenfelner did by using the 200 HP Subaru reduction drive on the 100 HP Honda.

Like I said, ALL the OEMs validate their designs with rigorous and prolonged WOT and full power tests these days and have been doing so for years and they do it with hundreds of engines so they have accumulated thousands of hours of WOT before release for production. A few recent examples:

Ford Eco Boost 1000 hours WOT peak torque to peak power.
Hyundai standard test 300 hours for all engines at WOT PP.
Dodge SRT standard 500 hours WOT TP to PP.
10 years ago the GM LS engines were run at WOT PP for 520 hrs. Teardown showed no appreciable wear.

You can say whatever you want about the Honda Fit (which I think is an excellent engine) but it does not have even a fraction of the proven flight time that Subaru engines do. I think the Honda Fit will prove equally reliable however given the same sort of testing it undergoes as all the others. Typically, we don't do any mods to Subaru engines internally except forged pistons for turbocharged ones in some cases. Screwing with the factory engineering is a bad idea in most cases.

Eggenfellner does not use the Subaru gearbox on the Fit, it is a new design and incorporates a rubber TV damper/ coupler. Too soon to tell if it will be reliable at this point.

The Rotax 912 "clutch" is only there for prop strike protection, it is never active during normal running. You can check various sources for this information. The "torsional damper" uses ramped, spring loaded dogs to minimize torsional peaks sent forward. These are two different devices. As far as I know, Rotax still does not recommend low idle speeds on these engines where TV can be pronounced even with the new kit.

Getting back to the original question, I am not aware of too many RV guys currently contemplating a Sube up front, there are a couple ex Egg FF packages floating around that people have bought up. There are a couple STi setups in process still with mods (certainly required). Of course the Sube is still a popular choice on many other non-RV airframes. There are some turbocharged Sube sixes close to flying now in a Cozy and Lancair so it will be interesting to see how those work and perform. I talked a couple guys out of Subaru conversions recently. They were not the type of guys to get involved in this. They'll be looking for mid time Lycomings now. RDM in the NW has been working on a new PSRU design and Subaru engines quietly for several years now, testing a lot. They don't say much which may be either good or bad. They posted this in 2011: http://www.youtube.com/watch?v=_ttLYNfIR-M

 

[SvingenB]

Forgot about the dogs (haven't been flying much Rotax lately). But the clutch is there to prevent overload of the gears. All certified engines have this clutch, and it is mandatory for non certified engines with CS propeller. Otherwise it is an option. When this clutch is installed, there is also a free play at the dogs, and it is this free play that can be heard and felt during start (it is not TV though) and is completely harmless due to the clutch acting. Flying at close to no load on the prop can also cause the same phenomenon.

Without the clutch the engine will not run properly at idle if the propeller is too heavy, and TV may start. The no-clutch option does not have this free play as far as I know.

The Verner 133 also have this clutch/spring setup, but without the free play. As with Rotax that engine also have billions of hours with few problems.


Anyway, 500 hrs of testing, what is that compared with year after year with countless hours of real life experience for thousands of engines in outboard marine application? Lots of them may not even be maintained properly, but they still run.

 

[rv6ejguy]

Anyway, 500 hrs of testing, what is that compared with year after year with countless hours of real life experience for thousands of engines in outboard marine application? Lots of them may not even be maintained properly, but they still run.

This is 500-1000 hours on a SINGLE example. GM, Fuji, Ford or Toyota may run 100+ pre-production engines through the same tests before release. That is 50,000 to 100,000 hours.

Again, there are only dozens of Honda Fit engines flying and only recently. There have been thousands of Subarus flying for the last 30 years starting with the EA81 which was designed as an aircraft engine from the start by Fuji. Well flight proven. The Fit is not at this point. The RAF gyro fleet using EJ22 and EJ25 engines had accumulated about 125,000 hours as of 2006 according to an owner survey, no doubt a lot higher 7 years later.

Are you arguing that the Subaru does not stand up to aviation use? If so produce some evidence.

 

[simpkinsona]

Anyone considering a Subaru engine should request to join the Subenews forum and do some research. From this you can glean what works and what doesn't.

Ross,

I'd consider using a dual mass flywheel for your next set-up. Mine has held up for 500ish hours now and my opinion (no proof) is that it does a great job of reducing the impulse loads on the gearbox when starting and shutting down. I think the combo of Gen 3 and dual mass gearbox yields a reliable package.

-Andy

 

[RV10inOz]

My own plane is all apart now after 9 years and almost 360 hours.

Ross, 360 hours is barely run in, and not a test of endurance. Double that in 3 years is more like serious use. The one RV down here that goes very well, as mentioned before has had the gearbox removed with an eye opening failure only a few hours away, and it would be about 360 hours

The engine itself is not so bad, apart from head needing valve work, leaking seals, coolant leaks, etc. Injectors clogging(yeah a Lyc injector would not have known) so while I know you and a few people can succeed with them, they have a hard road to hoe though.

Ongoing work and maintenance heavy is my observation, and that is of the most successful one down under. Gyro's that do local sorties and 30 hours a year ar not a good sample, even over 10 years. Unless they all regularly do 1000-2000 hours with little spanner work, they can hardly be compared.

Just my opinion, I understand some have a passion for the Sub's

 

[SvingenB]

Are you arguing that the Subaru does not stand up to aviation use? .

Not at all. What I am saying is Eggenfellners choice of using the Honda engine is a very good one because it is designed and tested and proven for a similar application with almost identical operation: outboard marine engine. The competition is fierce: Jabiru, ULPower etc and arguably the best aero engine ever produced, the Rotax 912. So far he is doing extremely well, and I believe one of the main reasons is he is using an engine that is more or less designed for it and one that has an unbeatable track record. He tried the Subaru, and that didn't really work out.

 

[shogan50]

He tried the Subaru, and that didn't really work out.

I wasn't real close to it, but it didn't appear to me that it was the engine that gave him fits. It looks to me like he started with the stock subaru ECU, had cooling system problems, 3 generations of gear boxes, less than ideal super charger installation, and lack of advertised power, lots of evolution of packages, high BSFC due to said supercharger.

The fact that jabiru and ULPower and Rotax all operate at a lower power output suggest to me that it might be an easier nut to crack, either financially or technically.

With the sport pilot regulations, that market has also likely become more attractive. If you were going to jump into that market, I'm not sure Subaru has an offering anymore.

 

[rv6ejguy]

Anyone considering a Subaru engine should request to join the Subenews forum and do some research. From this you can glean what works and what doesn't.

Ross,

I'd consider using a dual mass flywheel for your next set-up. Mine has held up for 500ish hours now and my opinion (no proof) is that it does a great job of reducing the impulse loads on the gearbox when starting and shutting down. I think the combo of Gen 3 and dual mass gearbox yields a reliable package.

-Andy

Subenews is a closed group only for Eggenfellner engine owners but I agree it is an essential resource for those owners.

Until a few people get a couple thousand hours on the dual mass setup, I remain unconvinced it will solve all the problems- in fact we see there are several problems with the gearboxes presently although some people have been fortunate to have no problems with the package at all. The real problem with the solid fywheel Egg setups was that there was no TV damper at all. In any case, a dual mass is not an easy option with my gearbox and I like to experiment so...

 

[rv6ejguy]

Ross, 360 hours is barely run in, and not a test of endurance. Double that in 3 years is more like serious use. The one RV down here that goes very well, as mentioned before has had the gearbox removed with an eye opening failure only a few hours away, and it would be about 360 hours

The engine itself is not so bad, apart from head needing valve work, leaking seals, coolant leaks, etc. Injectors clogging(yeah a Lyc injector would not have known) so while I know you and a few people can succeed with them, they have a hard road to hoe though.

Ongoing work and maintenance heavy is my observation, and that is of the most successful one down under. Gyro's that do local sorties and 30 hours a year ar not a good sample, even over 10 years. Unless they all regularly do 1000-2000 hours with little spanner work, they can hardly be compared.

Just my opinion, I understand some have a passion for the Sub's

Initially I was putting 100 hours a year on but life and work got in the way. A flying club puts on quintuple what you do in a year, so I don't see your point here. Of course and I've said this before, 350 odd hours is merely a start, doesn't mean much in the big scheme of things but we learn as we go.

Why did your friend's engine need valve work? Why were the seals leaking? Why was it leaking coolant? Why were the injectors clogged? I've been working with these a long time and so have hundreds of our customers. I can assure you these are not common ailments at all and suggests some very bad assembly, system layout etc. Leaded fuel use is not kind to the valves we have found. The rest of these things just don't occur for us. I had done NO maintenance on my engine except change plugs and oil.

The high time gyro was doing flight training work and flying about 800 hours per year. The RAF gyro survey indicated 13% had over 500 hours on them (2006).

I fly a Subaru because I am a gearhead and like to try and learn new things. I don't have any interest in flying a Lycoming powered RV. Your interest and mission are different from mine. Power to you. Enjoy flying your Lycoming. The initial question was asking what was new in the Sube power world and if there was still a reasonable movement towards their use in new RV builds. The basic answer is no.

All engines can experience problems, we've seen some recent posts about valves and rings going bad in Lycomings with not a lot of hours on them too. Diagnose, fix, move on, no drama, just some money and time. We all hope our engines go 2000 hours without being touched but not all do. Repairing an auto engine costs a fraction of the Lycoming, my total rebuild will be under $1000 for instance and I still have $40K in the bank by going with the Sube 9 years ago. The economics work for me.

As a moderator here, let's try to stay on topic if we can. Do we have to see every discussion about auto engines here on VAF degenerate into the same us vs. them?

Do I think the Subaru is a good engine? Yes. Do I think you should have one in your RV10? Nope and neither should most other builders and I have stated that many times. Not trying to change anyone's mind about engine choices, just providing information here for those with a genuine interest.

 

[rv6ejguy]

I wasn't real close to it, but it didn't appear to me that it was the engine that gave him fits. It looks to me like he started with the stock subaru ECU, had cooling system problems, 3 generations of gear boxes, less than ideal super charger installation, and lack of advertised power, lots of evolution of packages, high BSFC due to said supercharger.

The fact that jabiru and ULPower and Rotax all operate at a lower power output suggest to me that it might be an easier nut to crack, either financially or technically.

With the sport pilot regulations, that market has also likely become more attractive. If you were going to jump into that market, I'm not sure Subaru has an offering anymore.

Well said, there were never any core problems with the Sube engines, just too many untested external mods and business/ customer support problems.

 

[SvingenB]

As a moderator here, let's try to stay on topic if we can. Do we have to see every discussion about auto engines here on VAF degenerate into the same us vs. them?

That was not my intention. The point I am trying to make is that during the last 10 years there have been a revolution in the outboard marine engine industry. Going from 2 stroke engines exclusively (high power, low reliability and high fuel consumption) to cutting edge high power compact 4 stroke engines. Honda has been in front of this "revolution", they started it followed by Yamaha and Suzuki. Honda offers their engines now with 6 years warranty, all of them from 2 to 250 HP, all 4 stroke. That is not bad for a 1500cc 90 HP engine designed to run at WOT all its life. The design criteria for an outboard marine engine is very similar to design criteria for an aero engine I assume.

Eggenfellner takes advantage of this and is therefore able to deliver an engine that is designed to run at WOT as the normal operational range (well, almost since his engines are rated at 110 HP).

Only 10 years ago the only alternative was an auto engine, designed for auto use. Today there exist an entire range of engines from 2 to 350 HP (Yamaha V8 4 stroke) that are the absolute cutting edge in compact 4 stroke engine technology and they are all designed to cruise continuously at or near WOT. They offer 6 year warranty.

The rest of the conversion must of course also be designed to handle all that power, but as far as the core engine goes, any questions regarding the ability to run continuously at high power and questions about core reliability is not an issue.

I think Eggenfellner has done more than simply making a new conversion. He has taken the next logical step.

 

[rv7charlie]

Many, many auto engine designs have been used in marine applications for decades, & most have been successful. Some are just too heavy for a/c use, but the bigger factor is that there's serious highly $killed development of the systems around them when used in the marine environment.

In contrast (with only one or two exceptions), auto engines in a/c are basically one-off attempts by (usually) someone without the skillset to design & build the systems around the chosen engine. Concern about that issue made me think long & hard about trying one. But if I didn't, I'd be a little embarrassed to stick that 'Experimental' label on my -7 when it's finished.

There are lots of successful auto conversions out there (probably a minority of those attempted; see above), but most guys that are successful aren't willing to put up with non-stop attacks on internet forums (like this one) from the certified-engine True Believers.

My opinion is that almost any auto engine can be successful on the right airframe, assuming the right engineering/construction is accomplished on its systems. If Ford Model A's are successful, the motor isn't the issue.

Charlie

 

[rv6ejguy]

Many, many auto engine designs have been used in marine applications for decades, & most have been successful. Some are just too heavy for a/c use, but the bigger factor is that there's serious highly $killed development of the systems around them when used in the marine environment.

In contrast (with only one or two exceptions), auto engines in a/c are basically one-off attempts by (usually) someone without the skillset to design & build the systems around the chosen engine. Concern about that issue made me think long & hard about trying one. But if I didn't, I'd be a little embarrassed to stick that 'Experimental' label on my -7 when it's finished.

There are lots of successful auto conversions out there (probably a minority of those attempted; see above), but most guys that are successful aren't willing to put up with non-stop attacks on internet forums (like this one) from the certified-engine True Believers.

My opinion is that almost any auto engine can be successful on the right airframe, assuming the right engineering/construction is accomplished on its systems. If Ford Model A's are successful, the motor isn't the issue.

Charlie

Very well said. The successful conversions are just flown like a Lycoming with little fan fare and chest beating. It's the ones which are not successful we hear most about. People are obviously concerned about failures in aircraft. We generally hope they are slow, soft failures instead of catastrophic ones.

On another forum a few month back some members were posting that they had never seen any auto conversion go 1000 hours without problems or even 500 so I posted a bunch of links and examples that I know of.

If your mind is made up and closed or you are not in the loop, of course you might not believe any exist. In fact, there are hundreds of successful auto conversions flying all over the world and there are hundreds more which did not work out well but rarely is there an actual mechanical problem or failure of an unmodified core engine, usually something with the supporting systems or often people just do something plain stupid- direct drive Corvairs using poorly reground non-nitrided carbon steel cranks comes to mind here. Various auto engines forums are valuable tools to know what does not work as somebody has probably already tried it as well as to find out what does work.

Regarding marine engines, well almost every "innovation" they incorporate was used years or decades before in the auto industry. Auto engine design engineers are very smart people and understand exactly what is involved to make them reliable under any usage including WOT, high rpm continuous running. They also have a vast budget and tools to validate the design. Look at GMs new engine test center for instance. We never worry about catastrophic failure of a stock engine in aircraft really anymore than anyone else does. Running at 75% power and 70% of redline rpm is not taxing anything much. Much worse has been done in the validation period by the OEM. The strength of many modern designs is proof of the massive design margins. With no internal changes, engine like the GM Ecotec and Toyota 2JZ are reliable at double the stock output and around 200hp/L. With not very extensive mods they are capable of over 600hp/L for racing. I'd bet anyone here a dollar that a Lycoming 360 would not put out 3600hp for even one second...

Too many people mistakenly believe that because auto engines generally run at relatively low rpms and low hp they are not designed to be reliable at high rpm and high hp. Now if this were true, we'd see a lot of broken engines on the Autobahn or at the end of a track day weekend. These engines must be reliable under all usage including a flat out run on the Autobahn, some deserted road or a race track. If they blew up, there would be plenty of warranty claims. They are designed to take WOT for hours and days on end, just like a marine engine and they are tested just like a marine engine by beating them on a dyno for hundreds of hours plus undergoing far more stringent cold weather and abuse testing. Some of the tests GM runs their engines though are pretty hair raising with cold coolant pumped into a hot engine at WOT and articulated test cells which run the engine at high power while rapidly moving the engine through various angles and motions. Nobody tests their engine designs like the big auto OEMs.

 

[L.Adamson]

Many, many auto engine designs have been used in marine applications for decades, & most have been successful. Some are just too heavy for a/c use, but the bigger factor is that there's serious highly $killed development of the systems around them when used in the marine environment.

In contrast (with only one or two exceptions), auto engines in a/c are basically one-off attempts by (usually) someone without the skillset to design & build the systems around the chosen engine. Concern about that issue made me think long & hard about trying one. But if I didn't, I'd be a little embarrassed to stick that 'Experimental' label on my -7 when it's finished.

There are lots of successful auto conversions out there (probably a minority of those attempted; see above), but most guys that are successful aren't willing to put up with non-stop attacks on internet forums (like this one) from the certified-engine True Believers.

My opinion is that almost any auto engine can be successful on the right airframe, assuming the right engineering/construction is accomplished on its systems. If Ford Model A's are successful, the motor isn't the issue.

Sure, as long as someone knows up front, that they better be close to having an engineering degree, and are willing to spend many years of experimentation. Trouble is, there is a lot of sugar coating out there, which leads some down the wrong path. They're either looking for a cheaper alternative, or ended up believing over hype, in which the auto-conversion was billed as being much newer technology, along with more power. So yes, anytime it's sugar coated and over hyped.............then I'm glad this forum is around. Otherwise, too many can get screwed, just as they have in the past.

L.Adamson

 

[Snowflake]

I've been seeing this argument so long that i've learned to take both sides of it with a grain of salt at times. I still like the *idea* of a Mazda rotary conversion. I've always liked the rotary engine, even if it burns more gas than a conventional engine. It's neat engineering, with some significant benefits in areas other than fuel consumption.

 

[SvingenB]

I've been seeing this argument so long that i've learned to take both sides of it with a grain of salt at times. I still like the *idea* of a Mazda rotary conversion. I've always liked the rotary engine, even if it burns more gas than a conventional engine. It's neat engineering, with some significant benefits in areas other than fuel consumption.

I agree. You have to offer some kind of benefit. Eggenfellner does that with the price tag, half the price of similar performance aero engine (rotax, jabiru, UL etc).

 

[pierre smith]

Yaawn....

Gearboxes, radiators, ECU's and such.

Do you want to continually tinker, or would you rather fly?

Best,

 

[rv7charlie]

I've been seeing this argument so long that i've learned to take both sides of it with a grain of salt at times. I still like the *idea* of a Mazda rotary conversion. I've always liked the rotary engine, even if it burns more gas than a conventional engine. It's neat engineering, with some significant benefits in areas other than fuel consumption.

The burn penalty is about 10%. Contrast that with the fact that the rotary (as long as you aren't boosting it) actually prefers the lowest octane mogas you can get. When you contrast $3/gal mogas with $5.50+ avgas....

Not all the rotary installs achieve this, but quite a few do, which pretty much reinforces what I wrote earlier about the problem being something other than the motor. (And I say that with full awareness that I may be one of those 'other than the motor' issues with my installation.)

The real deal is learning new stuff. The RV kit is really just a big erector set. By the time the tail is built, we're just tweaking skills, not learning new ones. I've learned how to use a Bridgeport, discovered that I can no longer remember any Calculus, explored a lot of WW2 research; it's been a blast! The -7 project sat almost untouched for almost 2 years with a Lyc O-360 sitting next to it before I finally admitted to myself that I just couldn't do it, traded the Lyc for a nice car & dove off into my alternative 'universe'.

Charlie

 

[rv6ejguy]

The real deal is learning new stuff. The RV kit is really just a big erector set. By the time the tail is built, we're just tweaking skills, not learning new ones. I've learned how to use a Bridgeport, discovered that I can no longer remember any Calculus, explored a lot of WW2 research; it's been a blast! The -7 project sat almost untouched for almost 2 years with a Lyc O-360 sitting next to it before I finally admitted to myself that I just couldn't do it, traded the Lyc for a nice car & dove off into my alternative 'universe'.

Charlie

Atta boy! The average RV is experimental in name only for the most part. Glad there are a few of us who still want to think outside the box and learn something new. That is why I built mine, the cross country aspect is secondary but it does that fine too. No book could have taught me what I learned going the Subaru route and it has been a fascinating journey. It is very satisfying to experiment, design, make improvements and measure and see the results. I have no regrets using the Subaru, it has actually been very reliable and saved me a bunch of coin. That being said, tinkering is not for most people, they just want easy transportation and the RV/ Lycoming marriage is perfect for that.

You may be one of the first to ditch the Lycoming you already had! I'll be interested to see what you come up with.

Pierre, we don't really worry about ECUs or radiators these days. It is well understood what works now as there is a good track record of successes here. Gearboxes do need further study and testing for sure. Plenty of room for improvement in that department. So far the Autoflight and Marcotte are giving the best service. We hope the new RDM one will also prove to be good when it is released. There are plenty of other things to learn of course. That is what makes this interesting and fun for me at least.

 

[L.Adamson]

Atta boy! The average RV is experimental in name only for the most part. Glad there are a few of us who still want to think outside the box and learn something new. That is why I built mine, the cross country aspect is secondary but it does that fine too. No book could have taught me what I learned going the Subaru route and it has been a fascinating journey. It is very satisfying to experiment, design, make improvements and measure and see the results. I have no regrets using the Subaru, it has actually been very reliable and saved me a bunch of coin. That being said, tinkering is not for most people, they just want easy transportation and the RV/ Lycoming marriage is perfect for that.

That's correct! A lot of us have put a lot of time & money into these machines. I know that I prefer to fly............ rather than tinker, fly a bit, tinker some more, worry if it's going to fall apart, tinker some more, and so on. A friend of mine with a Subie did just that. I flew 120 hrs the first year, while he flew 13 due to over heating problems, and constant revisions of the cowl (adding more air "holes"), not to mention replacing
the gear box for the upgraded version. Granted, it was an "Eggenfellner H6".

Of course, if it's "macho" to be real experimenter for some, then so be it. It's not my thing in life to fly a little, and experiment a lot. I built a plane to see the scenic & panaramic mountain west. And that's exactly what I did. It was something I felt that I could trust. The Lycoming performed flawlessly from day one. Just like a "airplane" engine is suppose to!

Yes, I'm writing this because of the "attitude". Reminds me of someone saying we're lazy because we have an auto-pilot or rudder trim. It's true, RVs & Lycomings are not pure experimentation. But we still do far more, than someone who merely purchases a finished aircraft . Let's don't downplay that fact. When the day comes, that an alternative engine out performs a Lyc or clone, is lighter, requires less fuel, and has a good history with little failure............and not hundreds of hours of "experimentation", just to keep it running, and not overheating, then perhaps I'll change my own feelings. In the meantime, let's don't portray us as "simpleton's" who don't want to bother learning anything new. I read all the time......and what I've learned so far, is to stay as far away from alternatives, as I can get. Besides, airplanes are for flying......and not constant tinkering.

BTW--- If I ever do have the $ again, I'll certainly purchase a finished airplane. Something along the lines of a Aviat Huskey would do just fine.

L.Adamson

 

[rv6ejguy]

Never said anyone was a simpleton and I don't think experimenting is "macho". It takes tremendous dedication and drive to build an RV no matter what engine is fitted, nobody disputes that.

Just saying that different people have different desires and missions. I respect everyone who has built their own aircraft and is enjoying it for whatever purpose they choose. I just wish everyone would do the same...

Just wonder why people have to dump on people doing something different from the norm. Don't like it, don't do it.

 

[Mike S]

Just wonder why people have to dump on people doing something different from the norm. Don't like it, don't do it.

Well put, same here Ross.

 

[shogan50]

Ross, or anyone else,
where would you turn for reliable information on what works and doesn't if you were going to do essentially what Ross did - ground up subaru FWF?

 

[rv6ejguy]

Ross, or anyone else,
where would you turn for reliable information on what works and doesn't if you were going to do essentially what Ross did - ground up subaru FWF?

For general Sube stuff, you can search Flysoob but the format is not so user friendly and there is little consensus on some aspects, otherwise, just drop me an email with more details of your plans. I can give you some direction on where to go for parts, system layout, what has worked well for several high time users etc. I know most of the successful Sube guys (and unsuccessful ones too! ) Homebuiltairplanes.com is more alternative engine open minded (for the most part) and innovative minded, plus a lot more respectful of new or different ideas. VAF probably is not the best place to discuss this topic.

 

[Randy]

Scott,

To answer your original question at the beginning of this thread, yes I am flying my Sube powered RV. I guess I am one of the crazies that have hung in there and gradually over time most all of the real issues have been resolved.

I started with an Egg STI package with a roots blower on it. It would launch like a dragster at 52" MAP, but there were many problems to be dealt with at that point. I ditched the blower and went with my own turbo installation that worked quite well. The performance was better than what I see claimed by any other 4 cylinder powered RVs, but there were still some reliability issues to be dealt with, mainly due to my own learning curve on turbo installation.

After that I focused more on reliability and had an engine put together trying go get enough HP in a normally aspirated version. The reliability has been great. I have routinely cruised back and forth between AZ and CA with it and I really don't have to worry much about something breaking.

The power level with the NA engine has been somewhat disappointing though. I probably should be happy with it and just keep flying it the way it is but I really got addicted having adjustable manifold pressure. So now I will do another turbo install with a very specially built EJ25 short block mated to SOHC heads. I will use an Aerocharger turbo that eliminates the need for engine oil going to the turbo which is where I had my problems before. If my plans come together the turbo could grenade in flight and I will still be able to fly on to an airport of my choice...

These engines are only as good as the gearboxes that deliver power to the propellers. The Gen 3 gearbox from Egg is a crude design that has been mostly successful. I have over 300 hours on mine and the oil stays very clean. We are still learning in this area and there are some obvious improvements that can be made to that design. One of my next improvements to mine will be to install a good metal chip detector at the drain location to give me early warning of any bearing problems. None of these have fallen out of the sky but a few have had bearing problems. I like the idea of the chip detector for early warning just like my coolant level alarm etc.

It takes time for these designs to evolve into a good reliable package. I don't know of any one producing what we would call a firewall forward package and the ones produced in the past should have been called starter kits or something else...

Randall Crothers
RV7A

 

[David-aviator]

Scott,

To answer your original question at the beginning of this thread, yes I am flying my Sube powered RV. I guess I am one of the crazies that have hung in there and gradually over time most all of the real issues have been resolved.

I started with an Egg STI package with a roots blower on it. It would launch like a dragster at 52" MAP, but there were many problems to be dealt with at that point. I ditched the blower and went with my own turbo installation that worked quite well. The performance was better than what I see claimed by any other 4 cylinder powered RVs, but there were still some reliability issues to be dealt with, mainly due to my own learning curve on turbo installation.

After that I focused more on reliability and had an engine put together trying go get enough HP in a normally aspirated version. The reliability has been great. I have routinely cruised back and forth between AZ and CA with it and I really don't have to worry much about something breaking.

The power level with the NA engine has been somewhat disappointing though. I probably should be happy with it and just keep flying it the way it is but I really got addicted having adjustable manifold pressure. So now I will do another turbo install with a very specially built EJ25 short block mated to SOHC heads. I will use an Aerocharger turbo that eliminates the need for engine oil going to the turbo which is where I had my problems before. If my plans come together the turbo could grenade in flight and I will still be able to fly on to an airport of my choice...

These engines are only as good as the gearboxes that deliver power to the propellers. The Gen 3 gearbox from Egg is a crude design that has been mostly successful. I have over 300 hours on mine and the oil stays very clean. We are still learning in this area and there are some obvious improvements that can be made to that design. One of my next improvements to mine will be to install a good metal chip detector at the drain location to give me early warning of any bearing problems. None of these have fallen out of the sky but a few have had bearing problems. I like the idea of the chip detector for early warning just like my coolant level alarm etc.

It takes time for these designs to evolve into a good reliable package. I don't know of any one producing what we would call a firewall forward package and the ones produced in the past should have been called starter kits or something else...

Randall Crothers
RV7A

Good to read your post, Randy.

Congratulations on the success you have had.

Few pilots have hung in there like Randy - the smooth running purr of the Subby engine can be addictive

 

[shogan50]

Thanks for the feedback Randy. Knowing what you know, would you go sub again? I you are ever up to the Seattle area, I would love to see it. I'd also be interested in any cowl/plenum pressures/flows/temperatures you've taken.

 

[RV10inOz]

Scott,

To answer your original question at the beginning of this thread, yes I am flying my Sube powered RV. I guess I am one of the crazies that have hung in there and gradually over time most all of the real issues have been resolved.

I started with an Egg STI package with a roots blower on it. It would launch like a dragster at 52" MAP, but there were many problems to be dealt with at that point. I ditched the blower and went with my own turbo installation that worked quite well. The performance was better than what I see claimed by any other 4 cylinder powered RVs, but there were still some reliability issues to be dealt with, mainly due to my own learning curve on turbo installation.

After that I focused more on reliability and had an engine put together trying go get enough HP in a normally aspirated version. The reliability has been great. I have routinely cruised back and forth between AZ and CA with it and I really don't have to worry much about something breaking.

The power level with the NA engine has been somewhat disappointing though. I probably should be happy with it and just keep flying it the way it is but I really got addicted having adjustable manifold pressure. So now I will do another turbo install with a very specially built EJ25 short block mated to SOHC heads. I will use an Aerocharger turbo that eliminates the need for engine oil going to the turbo which is where I had my problems before. If my plans come together the turbo could grenade in flight and I will still be able to fly on to an airport of my choice...

These engines are only as good as the gearboxes that deliver power to the propellers. The Gen 3 gearbox from Egg is a crude design that has been mostly successful. I have over 300 hours on mine and the oil stays very clean. We are still learning in this area and there are some obvious improvements that can be made to that design. One of my next improvements to mine will be to install a good metal chip detector at the drain location to give me early warning of any bearing problems. None of these have fallen out of the sky but a few have had bearing problems. I like the idea of the chip detector for early warning just like my coolant level alarm etc.

It takes time for these designs to evolve into a good reliable package. I don't know of any one producing what we would call a firewall forward package and the ones produced in the past should have been called starter kits or something else...

Randall Crothers
RV7A

I would be putting in a chip detector and magnetic plug, the gearbox I know of here in Brisbane has had a nasty weld failure at about 360 hours. It is nasty, and it beats the heck out of me why hat bearing arrangement is used and why on earth there is welding of any sort involved.

I am in the industrial gearbox industry and all I can say is

Be careful.

Perhaps a scaled up Rotax box would be a good start.

 

[Randy]

Thanks for the feedback Randy. Knowing what you know, would you go sub again? I you are ever up to the Seattle area, I would love to see it. I'd also be interested in any cowl/plenum pressures/flows/temperatures you've taken.

Well that is a tough question. There have been many times that I really just wanted to pull the Sube off and spend 50K or so to put an airplane engine in the thing I don't think I would do it again, but I am not all that sorry that I have done what I have. It has been rewarding to see the good performance I had with the turbo and the reliability I have had with the NA engine. I have enjoyed solving the problems and seeing good results.

I guess the main thing is whether you really enjoy experimentation and can deal with having a large investment and still not be able to just go to the airport and go flying with your buddies that have "normal" engines in their planes.

For a person like me, it is irritating as **** to go flying with other RVs and deal with them getting smaller in the windshield. I did not have to deal with that with my turbo engine and I really look forward to having similar performance along with the reliability.

It should be a lot easier now than it was. There is much more information available now regarding what works and what doesn't.

Regarding cowl pressures, the important thing is to actually measure them and not assume anything about how air is going to flow. A simple gauge that measures inches of water can be had for under $50 and save many headaches if it just gets used. From my experience, radiators, oil coolers, and inter coolers will perform pretty well once the differential pressure across them gets up around 6 or 7 inches. It only takes a little leakage to allow the differential pressure to equalize and destroy the flow. Air scoops and NACA inlets cannot do their job if they are having to exit air into a high pressure area, like the inside of the cowling. The pressure in my cowling behind the radiators will have around 7" water column pressure, so to get good flow to another exchanger requires the air inlet or scoop to overcome this pressure before any flow can take place. It is easy to waste a bunch of time putting things together that looks like it will allow good air flow and cooling...

 

[rv6ejguy]

I would be putting in a chip detector and magnetic plug, the gearbox I know of here in Brisbane has had a nasty weld failure at about 360 hours. It is nasty, and it beats the heck out of me why hat bearing arrangement is used and why on earth there is welding of any sort involved.

I am in the industrial gearbox industry and all I can say is

Be careful.

Perhaps a scaled up Rotax box would be a good start.

I agree, the Egg Gen 3 gearbox is not a great design IMO. Welded gear parts don't belong in an aircraft gearbox and this will always be a constant worry for owners. It seems that some weld processes were better than others as many have had no problems to date while others had issues very early on.

There have been multiple other issues although not widespread across the board. A failure in the gearbox even if a "soft" failure is often the last straw for Egg owners. While fixes and new parts are being developed by the support group for the Gen 3, the best solution would be a new gearbox design.

 

[DanH]

I agree, the Egg Gen 3 gearbox is not a great design IMO. Welded gear parts don't belong in an aircraft gearbox and this will always be a constant worry for owners..... While fixes and new parts are being developed by the support group for the Gen 3, the best solution would be a new gearbox design.

Recall we did attempt to run a thread strictly limited to technical aspects of Egg systems, notable among them the Gen3 gearbox and the soft element flywheel (not a "dual mass flywheel"; it is not dual mass as applied here). Still, I completely missed welding in the gearbox. What is welded to what and how are they failing?

BTW, it seems like a pretty good example of why pushing for technical detail has merit.

 

[rv6ejguy]

Recall we did attempt to run a thread strictly limited to technical aspects of Egg systems, notable among them the Gen3 gearbox and the soft element flywheel (not a "dual mass flywheel"; it is not dual mass as applied here). Still, I completely missed welding in the gearbox. What is welded to what and how are they failing?

BTW, it seems like a pretty good example of why pushing for technical detail has merit.

After some input shaft failures, the solid flywheels were "grounded" and the "fix" was to install the "dual mass" flywheels on all engines and verify shaft alignment, the gearboxes did not use alignment dowels... There is little science behind this recommendation and I believe we could still continue to see various failures on the drives. F2 amplitudes do appear to be lessened noticeably with the dual mass though but who knows in the higher ranges without instrumentation. Some people still reported F1 problems on both flywheel types which is around 250-350 rpm and results in serious kickback as the engine fires just off the starter in some but not all cases. There appears to be a number of variations in parts Egg supplied after an extensive technical poll was conducted and people measured or took photos of what they had. These variations can maybe explain why some users have hundreds of hours of trouble free operation while others have had multiple problems with low time on the parts.

Two gears are welded together and in a place that is hard to inspect without a small borescope or complete disassembly. Welds crack or fail. I got a little lost with the many different problems cropping up and I'm just glad I don't have one of these boxes. Welding is of course a bit concerning on hardened and heat treated parts. I've done it in race car gearboxes but it has to be done carefully and precisely to be reliable. I simply would not weld gears used in aviation.

The group has some smart guys working on fixes and service/ inspection procedures, compiling tutorials etc. Without these, most guys would simply be lost. Kudos to the great guys in the group for stepping forward with this help.

 

[Jerry Cochran]

Lo, lo prices!

I agree. You have to offer some kind of benefit. Eggenfellner does that with the price tag, half the price of similar performance aero engine (rotax, jabiru, UL etc).

Yup. He also did that with his original 2.5 Subie which was alleged to have 165hp, but for some reason only put out maybe 75% of that or less ( HP loss in gearbox? Maybe.). His pitch was that it was equal to a Lyco O-320 at half the price and a lot of folks went for it. Let us hope that the Honda Fit engine works out better. Like the Subie, the Fit engine itself is fine in cars, that they were designed for. It's all the peripherals as noted here and elsewhere that are the tough nuts to crack. True believers may disagree...

Jerry

 

[simpkinsona]

Jerry hit the nail on the head. Egg over promised on the HP and spent the rest of his Subaru career on trying to improve it. This resulted in heavier, more complex motors and no end of suffering for his customers. If he had advertised it as 140 HP and claimed performance of a fixed pitch O-320, he would have been able to keep it simple and maybe succeed. With the electric adjustable prop, mine climbs and cruises like an O-320 fixed pitch.

-Andy

 

[rv6ejguy]

Jerry hit the nail on the head. Egg over promised on the HP and spent the rest of his Subaru career on trying to improve it. This resulted in heavier, more complex motors and no end of suffering for his customers. If he had advertised it as 140 HP and claimed performance of a fixed pitch O-320, he would have been able to keep it simple and maybe succeed. With the electric adjustable prop, mine climbs and cruises like an O-320 fixed pitch.

-Andy

Yep, he just really needed to listen to someone who really knew engines and guide him along with proper mods to them rather than ill-conceived and untested ones. The first engines which developed about 125-130hp were actually pretty simple, cheap, light and reliable but mostly suitable for planes which originally used O-235s.

The quest for engines to equal the performance of O-360 led to the supercharged 2.5 and Sti. The SC 2.5s actually worked better than the Stis which were a complete disaster from the get go. The core engines were great but the crippling mods made to them were an accident waiting to happen as many unfortunately found out. Fortunately, once the bad mods are addressed, the STi makes an amazing aero engine as we have proven a couple times now- blinding speed and comparable to Lycoming fuel flows and only a bit heavier.

The six cylinder engines were just plain heavy and saddled again with poor intake and exhaust systems, failed to match O-360 performance. Still , we have many people flying them that love them for their smoothness and they have not had problems to date.

If Jan had only stuck with the Sti, properly developed it, keeping the turbo instead of the Eaton SC and addressed all the other problems with the VVT system and EFI and built and tested a solid gearbox, he would have enjoyed great continued success I think. A lot of ands I know but the Sti was the right direction, wrong recipe. The Getson/Inkster 7 shows what can be done with the STi.

So the question that started this thread... If anyone is thinking about replacing an Lycoming with a Subaru, my recommendation would be an EJ255/257 based 4 cylinder or for someone wanting a superX, the 230hp EG33 six cylinder has proven to work well in several other aircraft.

 

[shogan50]

Anyone have an exploded assembly view of one of these gearboxes or photos? I've not followed, but as a mechanical engineer I'm quite curious.