@nugger but the key again with a wankel is the same thing you have with a normal piston engine - When you have insufficient tolerances you have to bridge the gap with parts that wear.

Normal piston engines had to have their top ends rebuild on the regular in the 50s. People judge a new engine design against reliability that was earned over millions of engineering hours.

The key is that at some point there becomes diminishing returns on a given movement, and we are probably pretty close on a piston engine.