[supercat]

I think we should be looking at external combustion too. Do a little research on Abner Doble and his cars.

What would you call an engine in which the working fluid was burned, but not in the piston? Aside from a turbojet. What would a reciprocating version of the concept be called?

[AntiBurr]

This is much like the Rankin cycle engine, but it used Freon and worked much like an air conditioner in reverse. Variations on this theme are the Dyna Cam and the Wankle