In its simplest form, a Wankel rotary engine has just two moving parts: the rotor and the output shaft. Compare that to modern piston cylinder engines, which have over 40 moving parts.

But aside from sealing, poppet valves don’t offer many advantages. Still, engineers kept pushing: better springs, VVT, and all kinds of breathing tricks: variable intake manifolds, forced induction, ...

Rotary valve could help propel craft to Mars one day Date: April 3, 2013 ... Rather than redundancy, where parts are duplicated so new ones can take over for failed ones, ...

Over-the-top rotary builds are an enthusiast tradition. ... "If you bought the best parts and you were the best tuner, there are still parts that'll break, like the valve springs.