Subaru Engine

M

MHarrow

Filing Flight Plan
Joined
Nov 7, 2018
Messages
5
Display Name
Display name:
MHarrow11
Hi so I am dabbling in looking at purchasing my first aircraft. At my local airport there is a gentleman that wants to srll his kitfox 3 with a subaru E81 the aircraft has been sitting for over 10 in a extremely nice heated and air conditioned hanger. No issues with the fabric or anything else. I am just worried about the engine. I am a A&P that works on on jet powered aircraft.

I have read some things about that engine that I don't like. I would be doing a full check-up on the engine and replaceing lines before flight. It was built by Subie-link if that helps. He has all the documents for it. I just don't want to buy a crappy aircraft. So what is the option on it should I buy with or without the engine.
 
Personally , I will only buy Rotax , Jabiru or UL power - auto conversions our out since my main priority is to fly the plane for fun ( as opposed to working on it for fun )
 
How many hours does the Subaru have on it? Auto-engine conversions seem to have more of a tendency to break early in their lives. About 20% of accidents involving auto-engined aircraft occur in the first ten hours, vs. about 6% of the traditional-engined accidents.
eng_hours.jpg

The innards of the auto-engine conversion seem reliable enough, but they seem to develop issues in the peripheral components, such as the ignition and PSRU.
eng_causes.jpg

Especially take a look at how the ignition system is set up. Ideally, there'll be two completely independent systems. At least, if there's just a single ignition setup, it should have two independent power supplies.

Mind you, half of the auto engines in the homebuilt fleet are VWs, so the above data may be skewed a bit. About 30% of the homebuilt auto conversions are Subarus, with a significant number of those in gyros.

Ron Wanttaja
 
Cooling issues also seem to ground a lot of conversions.
Do you want to fiddle f*** around or fly somewhere for pie?
 
Buy without the engine and don't look back. Decent engine but the PSRUs tend to have issues. Keep the Subi on the ground.
 
I wouldn't buy or fly in anything with a Subaru conversion on it.
 
Ted DuPuis said:
I wouldn't buy or fly in anything with a Subaru conversion on it.
Click to expand...
Funny, I'm considering this for a home built. My only real fear is torsional vibration shredding the PSRU (I think that TV is the bane of the backyard engineer; mostly, it's not recognized for what it is, and whatever mechanism fails becomes grossly overbuilt to survive). The engines, properly built, are quite bulletproof.
 
Kenny Phillips said:
Funny, I'm considering this for a home built. My only real fear is torsional vibration shredding the PSRU (I think that TV is the bane of the backyard engineer; mostly, it's not recognized for what it is, and whatever mechanism fails becomes grossly overbuilt to survive). The engines, properly built, are quite bulletproof.
Click to expand...

Have fun, I still won't fly in it. :)

The gearbox is the issue that most auto conversions have regardless of make. Ben Haas used a belt-drive on his Ford 347 in N801BH and it worked very well, something like a 3" belt that was normally used for driving something like a 12-71 or 14-71 blower on a top fuel dragster (where the blower by itself takes more horsepower to run than his engine made... by a lot). Even he had a few problems in development, having to beef up the unit a few times, but he got it there and was the kind of man to do it right and be dedicated to making the necessary changes and upgrades. I would've flown in his plane any day and wish I had the opportunity.

Like anything, it could be done. The track record on the Subaru conversions hasn't been good. To be fair, I wouldn't fly behind most other auto conversions, either. In fact, Ben's plane is the only one that comes to mind that I would fly in. For all the complaining people do about Lycomings and Continentals about being ancient, they do the job well. Rotax has gotten their 4-strokes also quite good. I would fly in one but I wouldn't buy one, mostly because I don't like how they sound.

E-AB is about being able to design the plane however you want. So while I'll say I won't fly in a plane with an auto conversion, I won't try to dissuade anyone from using one beyond that.
 
Close friend crashed in his RV when the Subaru engine failed. The "manufacturer" is well known as less than honorable yet he is now making another engine conversion. I would stay away personally.
 
If the kitfox has at least fifty hours on the Subi engine I would get the plane with the engine.
Less than 50, it starts to be a judgement call. When you dig through Ron's (@wanttaja ) data the vast majority of auto conversion engine related failures are within ten hours of major changes/install of the engine. By picking fifty hours, you should have confidence the builder worked out the kinks in the design.

The reality is with kit built planes, there usually is a greater body of knowledge to lean upon if you go with Rotax, UL, Lycoming.... The issues pretty much are identical; but more of the issues are "known"; therefore it is theoretically easier to address.

Tim
 
I currently have my second Subaru automobile. I love them as cars. They are fun to drive, quirky, and nearly unstoppable in inclement weather. I’d never fly behind one unless I had no other choice. Many have belt driven valvetrains and are interference engines, they are leaky, fueling (IMO) is so-so and you are always under the knowledge of impending head gasket failure - even if you take impeccable care of the engine.
 
I've heard of a couple cases where the flat-4 Suby's oil pickup tube fatigue-cracked and the engine locked up from oil starvation. I think they were powering cars at the time, but just sayin'. The PSRU issues are well documented, and that gearbox/prop combo could introduce new and dazzling vibrations that the Subaru engineers never imagined.

I'll take proven 1930's engineering of my Lycosaurus any day!
 
retpd2001 said:
Close friend crashed in his RV when the Subaru engine failed. The "manufacturer" is well known as less than honorable yet he is now making another engine conversion. I would stay away personally.
Click to expand...
Did the engine fail, or did the Egg drive fail?
 
I'd pass on anything with a subi, corvair, or vw engine. Too many issues and you give up a lot of performance. By the time you spend the money making an auto engine work, you are at or have exceeded the price of a purpose built aircraft engine. The only time I would start considering auto engines is if you need something over 350 hp as that's where there seems to be about the limit of most conventional aero engines.
 
Grum.Man said:
I'd pass on anything with a subi, corvair, or vw engine. Too many issues and you give up a lot of performance. By the time you spend the money making an auto engine work, you are at or have exceeded the price of a purpose built aircraft engine. The only time I would start considering auto engines is if you need something over 350 hp as that's where there seems to be about the limit of most conventional aero engines.
Click to expand...

About 10 years ago I sat in on the Great Plains (I think? Forget) seminar on the VW engine conversions at Osh. The thing that struck me was that, as the manufacturer (the guys who make money off of it) the guy did not make any bones about the fact that they weren't as reliable as the LyContisaurs, but they were less expensive and lightweight. He pretty clearly gave the impression that this was something that was only for a little VFR buzz around plane, preferably over favorable terrain.
 
I think the engines are as reliable as anything aviation specific when run within their design limitations ( cars ).

Looking at car engine reliability stats - we are talking here millions and millions of hours with very few engine related failures.

That’s what proponents of these engines like to bring up but of course it doesn’t rally matter since when bolted on a plane, none of that rally applies ...
 
Ted DuPuis said:
About 10 years ago I sat in on the Great Plains (I think? Forget) seminar on the VW engine conversions at Osh. The thing that struck me was that, as the manufacturer (the guys who make money off of it) the guy did not make any bones about the fact that they weren't as reliable as the LyContisaurs, but they were less expensive and lightweight. He pretty clearly gave the impression that this was something that was only for a little VFR buzz around plane, preferably over favorable terrain.
Click to expand...
The Corvair guys are the same way. Or they will say "with all these mods it will be every bit as good as a conventional airplane engine". Well those mods add up to more or as much as a field overhauled Lyconental and you do not get the performance. A 110hp corvair performs most closely to a 80hp Rotax.
 
I’ve flown a couple planes with auto engines. They’re fine. I think the issues are typically poorly done conversions that get weeded out early on in their life. If it had a decent number of hours on it and looks to be in decent shape, I’d buy it and fly it.

But no piston engines will be as reliable as a turbine. It’s just a fact of life. Not that it’s an issue for most of us.
 
skier said:
But no piston engines will be as reliable as a turbine. It’s just a fact of life. Not that it’s an issue for most of us.
Click to expand...

I'll make one caveat there. If you compare a certified piston aircraft engine to a certified turbine, I will agree with you 100%. Turbines also have inherent characteristics that make them more reliability. Even if you look at turbine certified engines when compared to over the road truck diesel engines on an hour basis, the numbers probably still favor the turbine.

However, we do have some experimental turbines, like the ones used on that... what was it... canard thing that crashed a couple years ago out in Mojave. I don't see them ever becoming that big just because the cost and fuel burn numbers make them pretty impractical for the aircraft they would be sized for, but I would not expect those to be more reliable than piston engines. Nor would I expect a high-time, non-maintained turbine (see skydive operations) to be more reliable than a lower time, factory new/reman, well-maintained piston.

Devil is always in the details.
 
MHarrow said:
Hi so I am dabbling in looking at purchasing my first aircraft. At my local airport there is a gentleman that wants to srll his kitfox 3 with a subaru E81 the aircraft has been sitting for over 10 in a extremely nice heated and air conditioned hanger. No issues with the fabric or anything else. I am just worried about the engine. I am a A&P that works on on jet powered aircraft.

I have read some things about that engine that I don't like. I would be doing a full check-up on the engine and replaceing lines before flight. It was built by Subie-link if that helps. He has all the documents for it. I just don't want to buy a crappy aircraft. So what is the option on it should I buy with or without the engine.
Click to expand...

Subaru was once a very popular conversion for homebuilt aircraft. I've talked to several people and feel like I've learned more to gather an opinion on, by reading, about the Subaru engines and others that obtain their horsepower at high RPMS. A substantially common denominator for problems with "the engine", tends to be with the reduction drive failing. There is lots of info if you Google reduction drives for auto conversions. You can have a perfectly good engine, but its something else to have a good power transfer to the prop. The planetary gear set up does a lot of work and takes a lot of stress as I understand it. The good news is that parts are cheap for a Subaru or other auto conversion. On the other hand, they are much more complex and don't tend to use (maybe never) simple magneto set ups. So, the ignition (ecu) has to work well under flying conditions. Any engine that sits for extended period always has to be looked at with some scrutiny, due to rust where you can't see it. I'm not an expert, just another guy building an airplane (for 10 years). Take my 2 cents with a grain of salt on this. Just add the opinion to others. Hopefully, you will talk to some people that flew behind a Subaru, who can really be a help.
 
I knew a couple of people who were quite happy with Subaru 2.5L engines. One had a Pietenpol, another had a gyro. The latter gentlemen was a bit of a tinkerer: he added a little 8 psi turbo to his engine, as he said "mostly for normalizing it" for New Mexico altitudes. He said he was getting about 230 hp. Neither of them had much downtime and attended pancake breakfasts in the area every month. I don't know if I would want a Subie in a traveling airplane, or a bushplane, but it seems working fine for around the patch flying. AFAIK, neither of the two were Eggenfeller conversions.
 
Old rusty Subarus are the popular choice for cabin strips in AK. Old cars that get occasional use at best. The motors are the least of anyone’s concern. They just keep running.
 
Is there no such thing as “prop technology” that could take the gear drives out of the equation? Is it just mechanically impossible to move air efficiently or safely with a prop buzzing at 4-5000 rpm with a different diameter or profile or number of blades? I imagine if it could have been done it would have been by now?
 
455 Bravo Uniform said:
Is there no such thing as “prop technology” that could take the gear drives out of the equation? Is it just mechanically impossible to move air efficiently or safely with a prop buzzing at 4-5000 rpm with a different diameter or profile or number of blades? I imagine if it could have been done it would have been by now?
Click to expand...
The propeller becomes noisy and inefficient as the blade tips approach the speed of sound.
 
455 Bravo Uniform said:
Is there no such thing as “prop technology” that could take the gear drives out of the equation? Is it just mechanically impossible to move air efficiently or safely with a prop buzzing at 4-5000 rpm with a different diameter or profile or number of blades? I imagine if it could have been done it would have been by now?
Click to expand...
I wonder if some sort of ducted fan would work? You also have gyroscopic effects on the crank bearings if direct drive.
 
Subaru's "Boxer" engine is a marvel of reliability and durability. I plan to buy another one very soon. The rest of the car is worthy, too, but the IP questioned the engine for sitting.
 
Do you know what Subaru spelled backward is? U R A Bus. That useful nugget aside, I would be hard pressed to fly anything that doesn't have an engine specifically engineered to be an aircraft engine. Gearboxes are a huge deal and a notorious weak spot for aircraft engines.
 
PaulS said:
Do you know what Subaru spelled backward is? U R A Bus. That useful nugget aside, I would be hard pressed to fly anything that doesn't have an engine specifically engineered to be an aircraft engine. Gearboxes are a huge deal and a notorious weak spot for aircraft engines.
Click to expand...

With 50 000 rotax engines out there , their overall reliability numbers are very similar to legacy lycoming engines , so a well engineered gearbox can be very reliable indeed.
 
Warmi said:
With 50 000 rotax engines out there , their overall reliability numbers are very similar to legacy lycoming engines , so a well engineered gearbox can be very reliable indeed.
Click to expand...

My statement and your statement agree.
 
Clip4 said:
When you finally get it fixed and take it out and drive it report back.
Click to expand...
My wife's previous car was a Forester. She ran it for over 10 years with almost no trouble. Although it was still running great, we decided it was time she got to have a new car. She didn't even want to look at any other make or model, we went and got her another Forester.

And the old one? We put it on Craigslist and had it sold for our asking price in less than 6 hours. The people that bought it showed up 8pm that night with money in their hand. They said they'd been trying to buy a used one for a while but every time they'd find one listed, it would get sold before they could get there to look at it. And we live in MI where most of the population was taught from an early age to absolutely hate any automobile that isn't made in 'merica by an 'merkican company.

If they're as sh*tty as you say, then its the best kept secret ever.
 
Grum.Man said:
I'd pass on anything with a subi, corvair, or vw engine. Too many issues and you give up a lot of performance. By the time you spend the money making an auto engine work, you are at or have exceeded the price of a purpose built aircraft engine.
Click to expand...

You must never have priced out a corvair or VW conversion. Their price does not come anywhere near a lycoming or continental. A VW with all new parts and converted for aviation use is about 7k. The corvair runs about 10k. An even bigger difference comes in if you go to buy replacement/overhaul parts. I just bought a set of pistons and cylinders for my aerovee. Total cost was $220. That was for 4 brand new pistons, 4 brand new cylinders, and all new rings. A aviation specific crank for the VW runs about $700 brand new. Show me a certified airplane engine that has those types of costs.

The reliability issue for most of these auto engines doesn't come from the engine itself but usually from poor installation. They are not as straightforward as a lycoming when it comes to baffling, fuel system installation, wiring, induction and exhaust routing, etc. There is no doubt that a certified aircraft engine is going to be more reliable but that is because the knowledge of how to build, install, and maintain them is better known by a larger community. An auto conversion can be made to be just as reliable but it takes more work, knowledge, and research to get it right.

Keith
 
kmacht said:
There is no doubt that a certified aircraft engine is going to be more reliable...
Click to expand...
That's the long and short of it right there for me.

I think Subaru builds a great car and very fine and reliable engine. But part of the reliability of that engine comes from the fact that when you install it in a Subaru, you are operating that engine in the environment and mission for which it was designed. Though its a very fine engine, if Subaru had been presented with the task of designing an engine to turn a prop in an airplane, they likely would have designed that engine differently than they did.
 
kmacht said:
You must never have priced out a corvair or VW conversion. Their price does not come anywhere near a lycoming or continental. A VW with all new parts and converted for aviation use is about 7k. The corvair runs about 10k. An even bigger difference comes in if you go to buy replacement/overhaul parts. I just bought a set of pistons and cylinders for my aerovee. Total cost was $220. That was for 4 brand new pistons, 4 brand new cylinders, and all new rings. A aviation specific crank for the VW runs about $700 brand new. Show me a certified airplane engine that has those types of costs.

The reliability issue for most of these auto engines doesn't come from the engine itself but usually from poor installation. They are not as straightforward as a lycoming when it comes to baffling, fuel system installation, wiring, induction and exhaust routing, etc. There is no doubt that a certified aircraft engine is going to be more reliable but that is because the knowledge of how to build, install, and maintain them is better known by a larger community. An auto conversion can be made to be just as reliable but it takes more work, knowledge, and research to get it right.

Keith
Click to expand...

There are often small continental engines 0 smoh for sale under 10k. Yes the components cost more to buy but baring unexpected circumstances you will likely never have to buy them. If you fly the industry average of 100 hours a year and take care of a C85 or the like you will likely not have to do anything to it for 20+ years. Worst case you do a top end with chromed cylinders for 1k. I'm sorry but an auto engine will never be as reliable. You are running them at a higher duty cycle using smaller components. The fact that everything has to be perfect for them to work is evidence of that. I used to be a supporter of auto engine conversions but the truth is most just don't work or don't perform well. By the time you throw the money at them to make them perform properly and last you could have just bought a conventional engine and not killed the resale value of your hard work. ymmv
 
And all other arguments aside, it should be mentioned that all the apprehension and caution being experienced by the OP when considering this aircraft purchase is to be just as expected from any potential buyers when it comes time to sell said airplane. EAB aircraft have a smaller pool of potential buyers than certified airplanes of similar performance. Put an auto engine in that EAB aircraft and you reduce that smaller pool of buyers to a fraction of what it was.

Which means you might be able to get it for a song. But you might have to take half a song when it comes time to sell it.
 
You must log in or register to reply here.
Back
Top