Well wankel engines don't suit themselves well to airplanes, they have three combustion chambers vs one and every body knows that three small cylinders are weaker than one of the same size. That is why they suck down more feul, three fires per a rotation vs one, you also have to add in the slightly rich setting to help cool it and the higher rpm that these engine like to run at. It works out to be almost twice the comsumptin of feul just to run at the same rpm as a compriable .[:-]30 two stroke.