Engine Configuration - Categorisation By Piston Motion

Categorisation By Piston Motion

Engine types include:

• Single-cylinder engines
• Inline engine designs:
  • Straight engine, with all of the cylinders placed in a single row
    • U engine, two separate straight engines with crankshafts linked by a central gear.
      • The square four is a U engine where the two straight engines have two cylinders each.
  • V engine, with two banks of cylinders at an angle, most commonly 60 or 90 degrees.
  • Flat engine, two banks of cylinders directly opposite each other on either side of the crankshaft.
    • H engine, two crankshafts.
  • W engine. Combination of V and straight, giving 3 banks, or two V's intertwined giving 4 banks.
  • Opposed piston engine, with multiple crankshafts, an example being:
    • Delta engines, with three banks of cylinders and three crankshafts
  • X engine.
• Radial designs, including most:
  • Rotary engine designs. Mostly seen on pre-WWII aircraft.
• Pistonless rotary engines, notably:
  • Wankel engine.

The standard names for some configurations are historic, arbitrary, or both, with some overlap. For example, the cylinder banks of a 180° V engine do not in any way form a V, but it is regarded as a V engine because of its crankshaft and big end configuration, which result in performance characteristics similar to a V engine. But it is also considered a flat engine because of its shape. On the other hand, some engines which have none of the typical V engine crankshaft design features and consequent performance characteristics are also regarded as V engines, purely because of their shape. Similarly, the Volkswagen Group VR6 engine is a hybrid of the V engine and the straight engine, and can not be definitively labeled as either.