Erik writes:

When I first started all of this I was completely amazed at the
similarities between a C150 engine and my VW Bug's engine.

Outside of a funnily-placed carb and another couple cylindars, you
could probably bold a C150 engine into a bug and run it just fine.

The technology of propulsion for small aircraft lags greatly behind the times.
I suppose there is little incentive to develop new powerplants and there are
high costs associated with getting them certified. Fuel issues in the future
and/or pollution or noise issues may force the hand of manufacturers
eventually.

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