Subaru Reality

A forum to alternate source of power to include Eggenfellner and other conversions.
yukon
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Subaru Reality

Post by yukon »

I feel your pain Chad! It's been three years since I decided againt Subaru power, but I still get up every morning and check the Egg website!
There's something very compelling about this concept.

Recently there have been two postings of Gen 3 H-6 numbers, and they are not very impressive. About 9 gph to do 170 mph. I'm figuring my 9 will make that kind of speed on 5.5 gph with a Lyc. The new gearbox seems to do little for performance other than taking the engine even further away from closed loop operation. That cut's your range and endurance almost in half, and that won't work for me.

You've got to give Jan credit for hammering away at this, though. I think he definitely represents the most persistent and successful auto motor
adapter in the history of experimental aviation. He's really quite a guy!

I think cooling drag is the biggest problem, because their efficiency is almost acceptable at best L/D speeds. At 120 mph, they seem to burn about the same fuel as LYC. Push it up though, better bring out that Chevron card. The turbo is going to eat them out of house and home.

Nobody talks about it, but a gearbox requires horsepower to turn, especially a wet sump spur gear running in 90wt. At high power, I'll bet
5-7 % of available horsepower is dissipated in the gearbox.

The earlier gearboxes were eating bearings, but how many is hard to determine. Hopefully, the G3 gearbox will solve that problem. On the other hand, I have heard engineering types say that you are asking for harmonic damage when you run at a reduction multiple so close to 2 to 1.
Time will only tell how happy those gears and bearings are at 2.02 to 1.

There is also a new ECU in developement which will hopefully improve fuel economy, and reduce potential problems related to sensor failure.

Anyway, I'm pressing on with my Lycoming install, and eventually an MT
3 blade. I think it will be smooth enough, but I'm sure I'll keep looking over Jan's shoulder in the hopes of my future Subaru.

John R.
RV-9 QB
Phoenix, AZ

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cjensen
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Post by cjensen »

Ha! I saw 'Yukon', and I thought "Oh boy, here we go!" :P Just ribbin' ya! Welcome to Rivetbangers John! Glad you're here!

I've had a hard time with my decisions about engines lately, but it's becoming more and more clear that the Egg Subaru's are just not in the ballpark for performance of what is expected from an RV. I know you're on the Yahoo group list, so I'm sure you saw these numbers this morning...from David Dormier's RV-7A flight yesterday...

EDIT: I should add that this is an H6/Gen 3 gearbox, but still two radiators. New one's have three...

Anyway, this is what I saw at 4500', WOT, rpm is prop speed.

RPM.FUEL/FLOW. KTAS
2400 12.5 161
2200 10.4 153
2100 9.5 149
2000 8.8 145
1900 7.6 140
1800 6.5 135
1700 6.2 131
Too slow, and too much fuel. The numbers are really unimpressive if you ask me. Jan is doing much more than anyone else in the industry, and I DO give him due credit. He is working on a wave for the future, it just isn't quite there yet. When they can get 170kts at 10gph or less using their current recommended rpm of 3800-4000 in an RV-7, I'll DEFINITELY look again. I'm probably going to resign to using the known quantity that'll give me my 170kts at 10gph or less that I desire for my 7.

Interesting point about the gearbox ratio. I don't know anything about harmonics, other than there are danger zones to operate in. I had never heard that somewhere around 2:1 could be dangerous. Interesting. I'm EAGERLY watching to see what they are going to do in the future. I just won't be able to wait long enough for the better numbers to come along.

I'm right there with ya though! I check the site each morning as well...
Chad Jensen
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yukon
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Egg efficiency

Post by yukon »

We are not talking about trivial amounts here either, we're looking at 20 to 40 percent overburns compared to Lycoming airplanes.

The 4 cylinder installations, while claiming 165 hp, are yielding the performance of a 115 hp RV-9.

Lot's of 'splaining to do here!

John R.
RV-9 QB
Phoenix, Az

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cjensen
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Re: Egg efficiency

Post by cjensen »

yukon wrote:We are not talking about trivial amounts here either, we're looking at 20 to 40 percent overburns compared to Lycoming airplanes.

The 4 cylinder installations, while claiming 165 hp, are yielding the performance of a 115 hp RV-9.

Lot's of 'splaining to do here!

John R.
RV-9 QB
Phoenix, Az
I TOTALLY agree. There are a couple of guys posting numbers that sound closer to reality (like those above). The Performance page factory numbers are unbelievable at this point.

20-40% overburns AND 15-18% REDUCED speeds is a BAD combination. :roll:
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Post by Spike »

Anyway, this is what I saw at 4500', WOT, rpm is prop speed.

RPM.FUEL/FLOW. KTAS
2400 12.5 161
2200 10.4 153
2100 9.5 149
2000 8.8 145
1900 7.6 140
1800 6.5 135
1700 6.2 131
Holy Crap, 161 kts at 12.5 GPH. If those numbers are indeed correct, I see Eggenfellner losing quite a bit of business. Its still early, but those numbers are not so great.
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cjensen
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Post by cjensen »

Yeah, I've FINALLY been able to crack the combination of getting some REAL WORLD numbers from these guys. They are WAY OFF from the factory claims at this point.

Several things come up when the numbers are posted, such as inefficient radiator cooling (drag) and "I need a better prop."

Too much gas, for too little speed.

I honestly don't see them losing a lot of business. I've come to realize that most everyone that is on board is there for reasons other than speed, and are willing to give some up.

Still interesting to watch as the numbers come in. I honestly think that they will get there someday, but the cooling drag has to be *better* than an air cooled engine, not just the same. :roll:
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Post by cnpeters »

Ouch. Those numbers are much closer to an RV-10 with the O-540. Seeing where fuel prices are going, fuel burn vs. speed is the largest variable for me. Valuable info - keep us posted.
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Post by svanarts »

There is always an out too. "The new engine, the new gearbox, the new prop will be faster."

I didn't want a Subaru for speed, I wanted it for smooth operation. I'm just not willing to give up that much speed for smooth operation. I still have time though. I'll just wait to see what the new engines are doing. I won't be holding my breath though.
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Post by svanarts »

A spreadsheet was posted to the Subaru forum on Yahoo. The max airspeed was 152 MPH, and the average fuel flow was just under 7 gph. I was hoping for a little more airspeed.

Chad, do you know which engine / prop combo Larry is using? I think he has an RV-7A?
Scott VanArtsdalen
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Post by cjensen »

I haven't seen the spreadsheet yet, but here's a quote from one of Larry's posts-
I have an RV7A H6 with the three radiator mod, dual cowl flaps and
the Gen2 Gear Box that flew for the first time two weeks ago.
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Post by cjensen »

I looked at the spreadsheet this morning. Another interesting thing is takeoff RPM. The factory states/claims 5400rpm (that's where 200hp comes) for takeoff. He never went above 4500rpm. Could be flight test/new engine proceedure, but it's not getting anywhere near 200hp. Actually, if you look at the table on the Egg site, 4500rpm is 165hp.

Another interesting document I came across this morning is RV-9A's with H6's and their weights-
RV – 9A ‘s with Eggenfellner Subaru H – 6 ’s


Name / Place / Flying / Empty Weight

Vic Abbey / Vero Beach – FL / Yes / 1250 Lbs

John / / ? / 1280 Lbs

Allan Christer / New York - NY / Yes / 1230 Lbs

Bruce Myers / Bend – OR / ? / 1256 Lbs
And those are all 9's!!

Wish I would've come across this info several months ago...
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Post by svanarts »

Actually if I was building an RV-9 the Subaru would be an excellent choice. I just want a little more speed out of my aircraft. Who knows... maybe the next generation of engine may provide more performance.
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rv6ejguy
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Post by rv6ejguy »

There is do doubt that the H6 installation is quite a bit heavier than a Lycoming installation. One other weight database shows this pretty consistently. Certainly unless auto engines are revved to their power peak rpm, they will not make their rated hp.

This was clearly the case on the first EJ25 engines which would never reach their 5600 rpm power peak rpm and proved to provide much lower performance than an O-320.

A turbo 4 gives lower weight than a six with higher power at lower revs. The best of all worlds.
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yukon
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Best of All Worlds

Post by yukon »

Ross,
With all due respect for your considerable prototyping and experimenting skills, I can't share your enthusiasm for this installation. Having read your website from top to bottom "the best of all worlds" is not the description that leaps to mind. Surely the weight and complexity of your turbo system and radiators comes close to that of the H-6. Also, cooling drag, reduction losses and frictional losses are still in play, making the direct-drive, air-cooled Lycoming, truely the best of all worlds.

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Re: Best of All Worlds

Post by rv6ejguy »

yukon wrote:Ross,
With all due respect for your considerable prototyping and experimenting skills, I can't share your enthusiasm for this installation. Having read your website from top to bottom "the best of all worlds" is not the description that leaps to mind. Surely the weight and complexity of your turbo system and radiators comes close to that of the H-6. Also, cooling drag, reduction losses and frictional losses are still in play, making the direct-drive, air-cooled Lycoming, truely the best of all worlds.

John R
RV-9 QB
I was making a comment mainly with engine choices here- a turbo four vs. an atmo six, not commenting on my test mule which as you say is somewhat of a mess with all those rads. Once I finish the RV10, I'm revamping the messy parts on the 6A to reduce weight, drag and complexity. I'd be happy to race you then!

Turbocharging is the only way these engines will approach the power to weight ratio of a Lycoming having 2 to 3 times the displacement at any reasonable rpm to give comparable fuel flows.

The weight of my FF forward installation is comparable to an O-360 and much lighter than the H6 installations. You can't sneeze at the speed it delivers. Never had any problem with the turbo system to date albeit with low hours on it. (working on the RV10 most of the time)

Every time I fly in a Lyco powered RV, the vibration and crudeness surprises me. The performance is just fine, they're just not for me. I'm not in aviation to do what everyone else is doing. A Lycoming powered RV is just like a 5L Mustang- everybody has one-yawn.
Ross Farnham

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Re: Best of All Worlds

Post by cjensen »

Two things stuck out to me...
rv6ejguy wrote:Turbocharging is the only way these engines will approach the power to weight ratio of a Lycoming having 2 to 3 times the displacement at any reasonable rpm to give comparable fuel flows.
I've never heard anyone say this. I believe it, but no one will say it or admit it (at least I haven't heard it). That's one of many things I like about you Ross...you are one of a few whom I think are TRULY honest with yourself and others about Subaru performance. So, thank you.
rv6ejguy wrote:Every time I fly in a Lyco powered RV, the vibration and crudeness surprises me. The performance is just fine, they're just not for me. I'm not in aviation to do what everyone else is doing. A Lycoming powered RV is just like a 5L Mustang- everybody has one-yawn.
I don't have a lot of experience in Lyc powered RV's, and even less in Subaru powered RV's. So, I guess this doesn't mean much, but the RV-7 that I fly in frequently with an IO-360 is VERY smooth, and the other Lyc powered RV that I've flown in had an O-360 Superior motor in it, which was the SMOOTHEST Lyc I've EVER flown behind...540's included. Now, neither was as smooth as the two Sube RV's I've flown in, but I couldn't tell all that much difference. Could be me... :roll:

John (Yukon), thanks for starting this thread...it has shed some light on a few things that aren't talked about all that much. :good job:
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rv6ejguy
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Post by rv6ejguy »

I should have added that my view on experimental aviation probably does not interest more than 5% of the RV community. I think most just want to enjoy flying their RVs without the tinkering I have done. What I do is certainly not for everyone and I tell most people who don't have the mechanical background to install the Lycoming. To date it IS the lightest and most proven engine for RVs out there.

For others who just don't want a Lycoming and those things that go along with them, Jan's conversions offer an alternative which generally have worked well. Just be aware that they will be heavier and probably burn a bit more fuel for any given TAS, especially at the top end. We'll of course have to wait for flight tests with the new prop, rads, ECU and drive to see how they really stack up. They are constantly being improved. The weight issue is harder to make competitive in my view so I don't see big changes here in the near future with the H6.

Fuel flow and hp wise- the reason I advocate turbos is simply to be able to produce enough hp at low rpms to cut the frictional losses present with higher revving atmo engines. This also permits higher drive ratios for better prop efficiency. Of course you also retain performance at altitude.

Jan has done an amazing thing and only when you are involved in similar work can you appreciate how difficult this task is when spread over several RV models and other airframes. To get every detail just right is immensely time and cost intensive. R&D is ongoing and people will have to be patient as Jan and Gary work to deliver a better product as time goes by.

To deny there is a weight or performance issue is illogical given the facts to date. When independent flight tests confirm or deny the numbers, we can then gauge relative performance more accurately. There have been issues with Jan's engines, particularly the STI but fixes have been developed and implemented. Considering the relative immaturity of these packages, I don't find this too distressing in light of the problems experienced by Lycoming with their mature designs. I think many people just don't have a grasp of the experimental roots of all Subaru engines in aircraft- they have not gone through the certification process like a Lycoming has. The core Subaru engine in my professional opinion (whatever that counts for) is more reliable than a Lycoming- period and has several magnitudes more running time. It is the supporting systems required when used in aircraft where problems generally surface- reduction gears, cooling, electrical etc.
These areas need careful design and validation through actual flight testing before the entire package becomes as reliable as the typical Lycoming installation.

Could more testing be done prior to release of a product? Of course, you can test for years and add that to the product cost until it becomes uncompetitive. At some point, you have to decide that everything is working well and release it. Almost certainly there will be issues that crop up as more products hit the market and time is built up on them. Even multi billion dollar designs from Toyota with huge amounts of design time and testing have had problems when released which must be corrected after release. This is part of mechanical engineering and manufacturing.
Many people just have to jump on every problem with a shrill "the sky is falling" attitude. Not a very useful attitude. In this field, we identify the problem, try to understand the cause and implement a solution we think will fix the problem. Move on to the next until we solve them all.

I am in touch with several OEMs who supply auto engine packages for aircraft. One thing they just hate is when clients decide to modify their designs then come to them when something doesn't work right! Duuuhhh!
While someone might have a better solution than the OEM, don't complain when it isn't!

We all have a choice of what engine we want to fly behind. While I like Subarus, I clearly understand they are not for everyone and I have no problem if someone decides to put a Lycoming in because I understand both sides of the coin. What bothers me is lay people generally from the Lycoming camp, constantly putting down alternative engines. There are advantages and disadvantages to both- fly what you like and enjoy the RV flying experience behind your engine of choice. :)
Ross Farnham

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Not the Best, Just Another Engine

Post by yukon »

Ross,

I understand the need to do something "different". We are all building instead of buying, so we all understand that concept. Notice though, we are all building the hands down, best all around experimental on the market, bar none!

For the last 3-5 years, Subaru converters have been representing themselves as the "best" engine for our aircraft. Fact is, it's not.
It's taken a while for the truth to get out, but now there's no denying that it's way heavier, way thirstier, and a fairly troublesome from what I can see. Still running hot, some are eating up plugs, others eating up gearbox bearings...........like you say, immature technology.

I like experimentation too, but I can see that this is a dead-end road. I have put away my auto engine aspirations because I can see that there are immutable facts of physics that will always make the air cooled, direct drive engine the smart choice for light aircraft. Sure I'd like an engine that is a little smoother, but I'll settle for one that is reliable and efficient.

Keep experimenting Ross, I know it is important to you. Just don't portray your Subarus as the "best", because they are not. They are a huge compromise in terms of weight, reliability, efficiency, complexity and performance. If Subaru guys would start telling it like it is, there would be fewer sad stories like Brian Mayette.

John R
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rv6ejguy
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Post by rv6ejguy »

John, I'm not sure where you get where I say that Subes are "best". My last reply was pretty clear in saying that there are advantages and disadvantages to both engines. My engine is better in certain categories than a Lycoming and worse in others- facts that I have published on many forums, my website and in magazine articles including side by side flight tests where no BS is present.

Frankly is is tiring. Most Eggenfellner users seem happy with their choices- some are not, just as some Lycoming owners wish they didn't have to install a second or third crankshaft or replace other defective internal parts while the vast majority have few if any problems.

Clearly people are interested in other things besides weight, speed and fuel burn or Jan would not still be selling over 100 FF packages per year. I think most people today are getting their facts from others over the net who have gone before them. Jan freely lets David and others post their real world numbers on his forum. He is hardly trying to cover up weight and speed figures. I would hope that anyone in aviation checks out any expensive product they plan to buy beforehand- avionics, props, engines, kits etc. Be as informed as possible so you hopefully will not regret your decision.

If people are scouting numbers, there have been plenty posted for Sube conversions in the last 2 years. The Van's flyoff with the STI a while back showed the differences in speed, weight and fuel burn compared to Van's demo RVs. Just as the Wankel flyoff a year earlier showed those differences. I applaud these owners for stepping up to the plate.

I hope you will be happy with your Lycoming powered RV.
Ross Farnham

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Building RV10 twin turbo Subie

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Easy Ross!

Post by yukon »

Asolutely false, Ross. Jan has been saying for years that his engines are comparable in installed weight to Lycomings. And that's with the plastic, $9000 prop installed. Now he's admittiting to the need for aft mounted batteries.......

The 4 cylinder was marketed as a 165 hp engine. Period. But everyone now knows that it performs like a 110 hp engine. I'm not seeing 200 hp on the h-6.........are you?

Jan used to tell eveyone how technologically advanced and efficient closed-loop operation is, until everyone discovered that you can't keep the engine in closed-loop at cruise power settings. Apparently when you cut the fuel pressure in to reduce burn, you also reduce atomization and fuel efficiency, because their burn is still way more than a Lycoming.

Ross, don't take it personally. I am very envious of the fine work you are doing on your RV-10. Your prototyping skills are second to none, and I wish I had half of your patience. I can't wait to see your numbers when that baby is completed (although I know numbers don't really matter) :evil:

Keep smiling! :)

John R
RV-9 QB 0-235-n2c
Lycoming Believer

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