wankel engine

A rotary internal combustion engine invented by Felix Wankel (1902-1988). It consists of an equilateral triangular member with curved sides orbiting about an eccentric on a shaft inside a stationary housing whose inner working surface is in the shape of an epitrochoid. The rotor is in sliding contact with the eccentric and imparts power to the eccentric shaft as a connecting rod does to a crankshaft. With one-third of a rotor revolution per shaft revolution and a power impulse for each of the three rotor sides, the Wankel generates one power impulse per revolution per rotor--twice that of what the four-cycle piston engine produces. Thus it has become accepted practice to multiply the geometry displacement of the Wankel by a factor of two for comparison with otto-cycle piston engines. The Wankel's advantages include compact size, light weight and smooth operation because there are no reciprocating parts. Its drawbacks include relatively high exhaust emission, possible sealing problems and low fuel economy. Mazda, however, has made significant improvements in all three areas.