How does a rotary Wankel engine differ from a piston-and-cylinder gasoline engine?

The Wankel engine differs fundamentally from a conventional piston-and-cylinder engine in its mechanical structure and operation.12

Key Structural Differences

• Motion: Conventional engines use pistons that move in a reciprocating (back-and-forth) motion within cylinders. In contrast, the Wankel engine utilizes an equilateral triangular rotor that orbits within a specially shaped casing.123
• Moving Parts: The Wankel engine is mechanically simpler, with the rotor and output shaft serving as the primary moving parts. It eliminates the need for reciprocating parts and spring-closed poppet valves found in standard engines.1
• Combustion Chambers: Instead of fixed cylinders, the Wankel engine creates three crescent-shaped combustion chambers between the rotor's sides and the curved casing wall, which vary in volume as the rotor turns.13

Operational Advantages and Limitations

The Wankel engine offers a high power-to-weight ratio, compact size, and smooth, vibrationless operation. Because it lacks reciprocating inertial forces, it can operate at higher speeds than traditional engines. However, it faces challenges regarding fuel economy and the complexity of maintaining pressure-tight seals at the rotor's apexes.1