Here is the VW tdi as an industrial engine.

Given the application I would expect there is a big honkin flywheel on
this thing that would be removed for aviation purposes. Then after
replacing the the alternator etc etc. It would still be heavy, but
potentially doable.

http://www.maesco.com/products/vwp/v...dieselpto.html

Anyway, it's something interesting to look at.

-Matt