Rotary Engine Facts

Rotary engines differ from traditional piston-driven engines. From their constantly moving rotor to their incredible power-to-weight ratio, rotary engines have somewhat of a cult following since Felix Wankel built the first prototype in 1957.

Size

• Rotary engines are notorious for their compact size while still delivering comparable power to engines twice as large. As of 2010, Mazda's latest version of the RX-8 is the only production vehicle in the United States powered by a rotary, sized at a paltry 1.3 liters in displacement. Because of the compact nature of the engine, it can mount farther back than traditional engines, lending to greater balance in the vehicle.

Benefits

• Wankel's design has fewer moving parts than a common piston engine. While a piston failure can destroy the entire engine, a rotor will continue to produce power until it eventually stops spinning, according to National Speed Inc. Because the rotor does not have to stop to change directions, rotary engines can run at speeds upwards of 9,000 revolutions per minute (rpm).

Function

• The rotor and housing create three distinct chambers, analogous to a piston's combustion chamber. In one pocket, formed by one face of the rotor and sealed by two edges, a fuel/air mixture is injected, compressed and ignited while the rotor spins around a stator, and the exhaust exits the chamber and enters the exhaust system.