Engine configuration

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Engine configuration is an engineering term for the layout of the major components of an internal combustion engine. These components include cylinders, pistons, crankshaft or crankshafts and camshaft or camshafts.

For many automobile engines, the term block is interchangeable with engine in this context, for example V block and V engine can often be used interchangeably in American English. This is because the most common forms are all based on a combined engine block and crank case that are milled from a single piece of cast metal. The locations of the major components are largely determined by the shape of this one component.

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 V-twin 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. The names W engine and rotary engine have each been used for several unconnected designs. The H-4 and H-6 engines produced by Subaru are not H engines at all, but boxer engines.

Categorisation by piston motion

Engine types include:

• Single cylinder engines
• Inline engine designs:
  • Straight engine, with all of the pistons are placed in a single row.
  • V engine, with two banks of cylinders sharing a single crank case.
  • Flat engine, essentially a V-block with the cylinder banks at 180 degrees from each other, as opposed to 60 or so for the V.
  • H engine, two crankshafts.
  • W engine.
  • Square engine.
  • Opposed piston engine, with multiple crankshafts, an example being:
    • Delta engines, with three banks of cylinders and three crankshafts
  • U engine, two separate straight engines with crankshafts linked by a central gear.
  • X engine.

• Radial designs, including most:
  • Rotary engine designs.

• Pistonless rotary engines, notably:
  • Wankel engine.

Other categorisations

The valve and camshaft position may also be considered part of the engine configuration, for example pushrod, overhead cam, overhead camshaft, DOHC, crossflow head.

Further reading

Piston engine configurations
Straight	Single, 2, 3, 4, 5, 6, 8, 9, 10, 12, 14
V	2, 4, 5, 6, 8, 10, 12, 16, 20, 24
Flat	2, 4, 6, 8, 10, 12, 16, H
W	8, 9, 12, 16, 18
Other inline	H, VR, Opposed, U (Square), X
Other	Hemi, Radial, Rotary, Pistonless, Deltic, (Wankel)