The Wankel Engine

The rotary piston engine invented by Felix Wankel (1902-1988) while working for the company NSU in Neckarsulm works according to the principle of the four-stroke Otto engine, but has triangle-shaped pistons (discs) instead of normal pistons, which rotate in an oval housing that is slightly narrowed in the middle.

The Wankel Engine Works Like This

During the rotation of the piston, its three edges form three chambers (A, B, C) with a variable volume together with the walls of the housing. During one turn of the piston, a complete four-stroke process with sucking in, compressing, working and expelling takes place in each of the three chambers. Therefore, three of the four power strokes always take place simultaneously in the three chambers, and after each turn of the piston, the engine has passed through the complete four-stroke process three times.

The piston is triangular, and its three equally long sides are curved outwards. During the turn, the three corners always fit tightly to the wall of the housing, as a result of which the centre of the piston (red in the picture) traces a circle during rotation. This orbit is caused by a shaft situated in the engine.

Advantages and Disadvantages of the Wankel Engine

Important advantages are the low consumption of material and the small requirement for space. On the other hand, there are disadvantages like the difficult realisation of a diesel engine, high production expenditure and high fuel and oil consumption.

For these reasons, the Wankel engine did not become established in cars. Only the company Mazda partly uses Wankel engines.