What would you have done? Go for the tried-and-true airplane engine, or save $10,000 and opt for a Subaru engine? (And is this really the right time and place to try and save a few bucks?)
Post your thoughts right here. (And we’ll try to track down Ed, too!)
A common problem w. non-aircraft engines in aircaft is torsional (twisting) vibrations of the crankshaft. Acft engine manufacturers analyze and measure these, then make modifications to alter the resonance frequencies so that the problem is minimized.
You can’t easily do that as a home builder. Be very careful. Historically, torsional resonances have broken both cranks and props.
Though it can be done I am sure, if I were capable, I would not use any car motor not usually used as a plane motor any more then I would use one for a marine engine. You see many used that way, but they are often not just off the shelf and have been modified. An engine that breaks or stalls while in the air has different ramifications then one on the highway.
My dad talked about flying a Model A powered plane that would cut out at too high an angle of attack (carb issue?). Once he knew that (not told beforehand!), it was a pleasant plane to fly.
Since this will be registered as an experimental airplane, why no use a car engine? 1940’s engine technology versus 2010 or so. You will likely need a gear reducer for the prop as the Lycoming and Continental aircraft engine turn very slowly compared to car engines. Its been done before pretty successfully with Chevy V8’s, Subies, VW beetle engines and others. Porsche sold a version of their flat 6 air cooled 911 engine certified for aircraft use. Of course that greatly increases the price!
Not that difficult to convert say a small block chev to marine use,but a number of chevy SB engines(Rodacs maybe)have powered record setting experimental planes,for liability reasons play it safe and buy the overpriced dedicated aircraft engine,its alreadt got a lot of the problems solved,sure they use porsche,VW, even metro engines for experimental aircraft,but most of the time you have to use a gearbox to match the engine characteristics and different problems,lastly,you dont think that the FAA really wants a whole lot of people flying private planes do you?(sorry IF I’m disjointed,keep getting interuppted)
My bud with a kit plane bought an air cooled twin magneto 6 cyl fuel injected Lycoming rebuilt engine in 2001 for 26k. If I recall correctly max speed 220 mph.
I guess I’ve been visiting here too long. Didn’t we have a long discussion about this a few years ago? Me, I’d want the time-tested old tech while I’m flying with one engine to keep me airborne.
Does your aircraft need the power of a Subaru or Continental/Lycoming (aircraft) engine? Will there be weight and balance issues? Would a Rotax engine be sufficient?
Subaru engine must, I assume, be liquid cooled. Also, the idea of gear reduction adds weight and maintenance issues, in my mind. (geared aircraft engines are notorious for high maintenance requirements). If you go that route, beware of descending with low power; the prop could exert negative torque–the prop puts a reverse load on the engine power train. And, how would you regulate the fuel/air mixture with an automotive engine? Aircraft engines different mixtures for takeoff, climb, and cruise at different altitudes. But perhaps you won’t be flying high enough to require leaning for cruise.
So many issues!
Me, I’m not using any engine designed for automobiles in my airplane. If I had an airplane I mean. Automobiles, relegated to the solidness of terra firma, are perfectly safe even if the engine quits. They’ll just putter to the side of the road; airplanes, not so forgiving.
My dad talked about flying a Model A powered plane that would cut out at too high an angle of attack (carb issue?).
My dad used to tell the story of how he’d have to back his Model T (I think) up steep hills. I think the reason was that car didn’t have a fuel pump, the gas delivery was on a gravity feed system, with the fuel tank in the back. If you tried to drive up too steep of a hill, with the gas tank below the engine level, the fuel couldn’t flow to the engine.
