The Wankel engine, more commonly referred to as a rotary engine or rotary combustion engine, is a type of internal combustion engine developed by Felix Wankel. As its more common name suggests, it's a rotary engine which means it relies on a much different mechanism than a traditional piston engine. Both piston engines and Wankel engines rely on the pressure created by the combination of burning fuel and air. A Wankel engine, however, relies on a rotary design rather than reciprocating pistons. In other words, a Wankel engine is a pistonless rotary engine.
A piston engine confines the four stages known as the “Otto Cycle” — intake, compression, combustion and exhaust — within an individual cylinder. First, the air-fuel mixture is allowed in, which the piston compresses as it rises toward the top of the chamber. The spark plug at the top ignites the compressed air-fuel mixture and forces the piston back down. This cycle causes the rotation of the connector rod and crankshaft. In the case of a car, the rotation causes the vehicle’s wheels to spin. Most vehicles have several cylinders. An engine with more cylinders, naturally, can generate more power.
A Wankel engine spreads the phases of the Otto cycle among the areas of a special oblong casing. This casing contains a single triangular rotor which is used instead of pistons. The spinning rotor allows in the air-fuel mixture, and then, through the same motion, compresses it into a smaller chamber of the housing. The air-fuel mixture reaches maximum compression by the time the rotor reaches the spark plugs, setting the stage for combustion.
Since a Wankel engine has fewer parts than a reciprocating engine, it is lighter and often more reliable. With a Wankel engine, there’s no need for parts such as valves, valve trains, and connecting rods — types of hardware that can greatly increase an engine’s weight. Wankel engines drive vehicles as diverse as motorcycles, aircraft, watercraft and even certain kinds of racing cars.
Despite its more compact size, Wankel engines are often less powerful and less fuel efficient than their piston-using counterparts. The American Motors Corporation (AMC) planned to begin using Wankel engines in its vehicles, but abandoned those plans amid the oil crises of the 1970s. Mazda has made use of the Wankel engine, most notably in its line of sports cars such as the RX-7 and RX-8, although it too has mostly turned away from them because of fuel consumption worries.
Felix Wankel, a German engineer, developed the engine bearing his name in the 1950s and 1960s with the help of NSU Motorenwerke AG. He first conceived the idea in 1924 before finally seeing the first prototype at work in 1957.