My opinion of the Mazda rotary engine is more subjective than objective. I used to own one of those engineering mistakes. The car backfired all the time, gave poor gas mileage and the engine needed to be rebuilt after only 60K miles. In the early 70's that was a lot of money for someone who bought the car to economize.

Mazda mass produced their product before it was fully developed. Their rotary engines were pulled from the market because they did not meet power expectations, were unreliable and the public quit buying them.

Coates delivered a working prototype generator set to China last November and to my knowledge has been in operation since.