The internal combustion engine, for all its mechanical sophistication, still runs on a 19th-century mechanical idea: pistons rising and falling, a crankshaft spinning, a steam-age architecture ...

The rotary engine was an unconventional design that delivered great power for its size. Here's what's good and bad about it.

In theory, Wankel-style rotary internal combustion engines have many advantages: they ditch the cumbersome crankcase and piston design, replacing it with a simple, single-chamber design and a thick, ...

Wankel rotary engine powered thousands of aircraft. One of several problems: It spewed castor oil on its pilots.