Needed: A twin: The Engines.

Needed: A twin: The Engines.

Ahoy, EAA Engineers, Designers, Builders:
There are a lot of new/small/powerful/lightweight engines out there -- serious candidates for flight. Many are suitable for development on this airframe. Appropriately 'beefed/sized' to handle a LOT of soup, this general airplane configuration would accommodate such as the Cadillac 2.0 T @272 HP, or Ford 2.3R @315 + HP. A pair of these -w- PSRU/prop is serious economical power, for a VERY fast airplane.
A certificated airplane engine produces about one half horsepower per cubic inch displacement, and is very reliable and simple. The above engines (are able to) crank out more than FOUR TIMES that power density! They include many sensors, computer(s) and thousands of lines of computer code. They are very reliable at normal automotive output levels -- 10% to 20% of max. Airplane engines run at higher power levels. If this high power output in an airplane induces a fault in this (auto) engine, the power is reduced to defend the engine (get-home/limp-home mode) to less than the power which is needed for flight.
If you manage to subvert this 'defensive' mode in order to maintain flight, the engine may well retaliate by exploding! If you 'de-rate' the engine, and develop acceptable reliability, it will likely have far less power, and it won't be cheap.
Because of the above factors, I have no knowledge of a way to make a modern very high output automobile engine acceptable as a single propulsion engine for an airplane, except for a very slow landing speed version (or a racer, with their risks). So: Use a PAIR.
These VERY highly stressed modern engines are so very long-lived and reliable, (at automobile output levels) that the drivers are smashing far more cars than there is a demand for engines. Excellent engines -w- controls/'gozintas' -- are relatively cheap, and should not need very much 'optimization' to be OK for flight __ as a twin. Like: Don't mess with the 'get-home' mode, because your second engine is your 'get-home' mode. With two of them aboard, one can comfortably establish how much reliable continuous power you can take from them. Fuel burn alone ( -- Like 50+ gal/hr) will keep you from running them very hard for very long, and at somewhat lower power, they are very efficient, and likely to survive quite well, and still 'go-fast'.
Every one of these engines will need a PSRU, and here is a rather formal discussion of PSRU's: (edited by a guy who builds good ones).
PSRU -- A Propeller Speed Reduction Unit is a mechanism which drives the propeller at a lower speed (RPM) than the engine crankshaft is turning, by means of gears, belts, or chains. That is necessary when the engine develops the required power at a crankshaft speed which is higher than the speed at which a propeller can safely or efficiently operate. There are many PSRU's available in the marketplace. Some are very good, but others have demonstrated very inconsistent reliability.
There are PSRU's which have been directly copied from problematic previous designs, and which demonstrate exactly the same problems as did their predecessors. Suffice it to say that a PSRU done by an enthusiast with a good fabrication shop, but 'unlettered' in his ability to calculate and then measure the dynamic behavior of his construct can be quite dangerous. Make sure that you know whose work you have, and that the person has a demonstrated grasp of the engineering principles involved.
So: Why all this talk about PSRU's???? While there are many issues about alternative engines, the most consistent and dangerous problem is with the PSRU. While the 'get-home' mode can let you down, an exploded PSRU (or engine) can KNOCK you down!
Enjoy /s/ Bob
Robert H. Belter
rhbelter@comast.net
EAA # 8444, EAA TC # 4561, EAA CH 204,

Ahoy Bob!

You've been in this game long enough to know that there have been a whole slough of auto engine conversions: Pietenpol, Funk, Waterman/Studebaker, Geschwender, Revmaster, AeroVee, Great Plains, Hummel, Blanton, Raven, Better Half, and a bunch of others. There have been many mechanically successful conversions done and many of them received great fanfare and adulation, but very few were commercial successes. The same holds true for twin engine homebuilts. I believe the main driver of auto engine conversions is the high purchase and maintenance costs of certificated engines. Back when it was common practice to save 10% of your income for retirement, most people didn't have a lot of spare cash to invest in an airplane. Today, we seem to "live in the moment" and credit is cheap, so the kit is king. Very few homebuilders are still entrenched in the grass roots of yesteryear, scrounging materials and parts to complete their own design, which may include a converted auto engine. Once you've spent $25K on a kit and $20K on the panel, common sense dictates you spend ~$30K on the engine and prop to protect the previous investment. Many view the airframe as the "experiment" and are cautious about compounding the "experiment" with an "experimental" engine, so they go with the known, albeit expensive, quantity of a factory built aircraft engine.
It comes down to personal choice based on an individual's disposable income, time available, skill set, confidence, and passion. There used to be awards given out to the best auto engine conversion at some of the larger fly-ins and maybe they still do. Pat Panzera is the most passionate person I know when it comes to promoting "alternate" power for homebuilts, and if it weren't for the amazing stuff he gets to witness, he'd probably be one of the most frustrated people I know.

Ahoy, Crusty,
First auto engine conversion I saw (as a boy) was an Aero Sport with a Ford V-8 engine in it. Off the end of the airport- across the road- with the gear knocked off. Would not quite fly on that hot Minnisquito day.
The airplane does not even show in Google. Low wing, strut braced, quite a nice looking airplane --sort of like the Kinner Sport -- Maybe the same?? It's been a while.
I guess that some are good, others notso.
Be interesting to see if this post generates some continued interest in a push-pull twin.
A 'pair' does solve a lot of the reliability/get-home mode problems with these very high output new engines. One need not way de-rate them to try for reliability.
Just make sure that they don't both go 'lame' at the same time. Early flight cooling problem could be one. One reads of early first flight aborts due to such. Easy to solve with distilled water spray bars, but folks don't seem to do that.
Thanks for your comments.
Enjoy /s/ Bob

Modern auto engines are, indeed, wonders. Powerful, reliable, adaptable. On the face of it, they would make great aircraft engines. The problem, as I see it, is one of complexity. Auto engine computers, fuel injection and cooling systems are all very complex. This complexity is, in my opinion, enemy of experimental aviation. Look at the few succesful auto engine conversions (VW and Corvair): they are based upon simple (ancient) engines. They are air-cooled and they are direct drive. They are, in fact, very much like the archetypical ly-cons. One need only look at the history of Subaru engines to understand how these added complexities increase the difficulty of achieving any kind of reliability. The Subaru is horizontally opposed, but it requires a PSRU. Electronic fuel injection and computer-controlled ignition sound really great, but the requirements of automotive use make them very difficult to adapt to aviation. Liquid cooling adds weight and increases the number of points of failure. I'm not arguing against trying to use modern auto engines, just saying that the enormity of the task should not be underestimated. Interestingly, we do have a prepackaged modern engine available to us: the Rotax 912IS. The engineering effort behind it is enormous, Rotax has a very large corporate parent behind it to support such an effort. And, as we all know, it is an expensive engine.

RHBELTER, We rebuilt an Aero Sport for Dolph Overton's Wings and Wheels Museum in Santee, SC. Ford flathead V8, spun the prop reverse from typical, and had some aftermarket engine mods (Edelbrock racing manifold, etc) on it. Ran rather well...my father had hot-rodded many a Ford V8 (in cars) and was tickled to have such to play with for awhile. HE flew it once (well, technically a very high speed taxi.....!). I've got to dig up my pictures.