"Richard Kaplan" wrote
What piston engine design would be more reliable? (Economics make turbine
engine comparisons unfair, even if turbines are more reliable -- and I am
not certain that they are.)

First off, turbine engines are not out of the questions at all. The
reason they are so incredibly expensive has a lot to do with the FAA
and milspecs. Second, turbine engines are inherently more reliable -
there are far fewer moving parts, and no reversals of direction. In
addition, they separate the combustion stages (suck, squeeze, bang,
blow) in space rather than in time - and that means only a relatively
small part of the engine has to be tough enough to accomodate the most
difficult portion of the cycle. In other words, pound for pound the
turbine will always be more reliable.

Second, we've learned a lot about piston engine reliability in the
past half century. Little of that has made it into aircraft engine
designs. For example, separate cylinders are disasters. There's not
sufficient mechanical stability, so everything moves too much. Note
that the two modern aviation piston engines - the Thielert and Orenda
- have abandoned that nonsense.

That's just one example. There are countless others in the ignition,
fuel, and other systems.

I have experienced a lot more engine problems driving cars than flying
airplanes for sure.

Driving cars made in the last 20 years? I find that amazing.

Experimental airplanes do not seem to have any lower incidence of engine
failures anecdotally, nor do I recall reading any data to suggest there
exists a more reliable experimental piston engine design.

Experimentals are amateur-designed. The engine installations are
amateur-designed too. The very fact that after the first 50 hours are
flown off the accident rate appears to even out with the certified
airplanes should suggest to you what a disaster the FAA-mandated
professional engineering is. Amateurs can do almost as well working
in their garages.

Michael