R - Rotary engine
Rotary engine - An unusual engine design, as used in the Mazda RX-8, which does away with conventional cylinders. Instead, it uses a triangular rotor which turns in an oval chamber to create combustion chambers in which the fuel is burnt.
The design is far smaller and lighter than a conventional engine, and is also smoother thanks to lower levels of vibration. However, rotary engines tend to be less fuel-efficient and create more emissions.
The rotary engine was created by Dr Felix Wankel in 1957 and is still known as the Wankel engine.