I'm talking about Carnot Efficiency. . . I think a good piston engine runs on the order of 20-25% and a Wankel running in the 15-ish % range. . .
Of course the power output is only one piece of the puzzle, but I was just curious. I've always been fascinated by the rotary engines in those RX-7s (wanna-be 944s!
).
The power-to-weight ratios are very good, despite the fact they're less efficient with their chemical-energy-to-kinetic-energy conversions though.