I wonder if maybe the Wankle rotary motor shouldn't be classed by itself.
If you look at the design, it almost would qualify as a turbin more than a reciprocating motor.
The sound of a improperly rotary is almost like the old IRL cars, sickening. Very few have been done correctly and sometimes the piping has to be folded because the car is not long enough. Adding a turbo or two can really make some HP, not to mention some real heat. Some of the drifting guys are running this setup, really long powerband and steady torque.