Norton Motors have developed the mechanically-simple air-cooled-rotor-type of Wankel engine to have a higher specific output than the oil cooled rotor type. The paper traces the development over a thirteen year period and describes the present design.
A characteristic of the engine is the very low mechanical friction. Mainly resulting from this factor, the specific fuel consumption is similar to the best four-stroke reciprocating engines. The potential exists for further improvements.