So, no one ever use a VW engine in an aeroplane??
Yes, Back in the mid '80s I redesigned a KR2 for a customer, wider, longer and new flight surfaces.
The engine was build by a very good machine shop in Conn whom was a VW specialist for a few decades at that time.
This engine if I recall was a 2375cc.
The first iteration had an off the shelf intake manifold. This was our first mystery due to very poor mixture balance.
It took me 3 tries till I fabricated a suitable intake with accurate mixture to each cylinder. I had the intake and exhaust all working in harmony with the camshaft and displacement.
Now with the engine finally fitted on the airframe we went through the rest of the pre flight prep.
During one of the last work sessions the owner "blipped" the throttle. This resulted in a splintered blade on the Great Planes prop. I had been questioning the durability of a wood prop with just 3 layers of lamination. The replacement prop was properly made.
Now time for flight. We soon found that NLF airfoil with it's cusped trailing edge with it's high pitching moment, just what that meant. Now this KR2 I designed has drooping ailerons such that the plane has full span flaps. Even thought I added length to the fuselage as well as larger tail surfaces we now found when slowing down on approach we ran out of elevator. easy enough to add camber to the underside of the horizontal.
Now we had a VW powered plane with a top speed of 175ish, cruise in the mid 150s and approach speed over the fence of 30. Not bad and you can see where my design is based on the plane I am currently building.
Now back to the VW engine, it did not take long for the Claudes Buggies Crankshaft to fail, It broke at the center main. The owner was able to reach an airport where the airframe was stored for many months while the engine was rebuilt.
If I recall the new crankshaft was sourced from Scat, the Claudes Buggies Crank was a one shot Chinese forging.
New case was needed.
Now back together, not many hours later an oil leak developed. Soon determined to be a major case failure forward of Cyl 3. The plane made it home this time.
I was no longer in the area at this time having started my restoration business on the other side of the state but If I recall a Scat case was now used.
This plane was flown for a bit over 10 years when the Owner went on to build an RV6.
Our analysis of the VW Motor in the long run. It turns at too low an RPM and is stuck in a critical harmonic range in aircraft use. A reduction drive allowing for moving the rpms up would warrant both a greater life as well as improving fuel burn and power.
Personally if an O-200 fits, I would fly behind it.
I think that VW motor ended up costing more than a little Continental will over the 10 years.