Multi-cylinder engines are produced in four common configurations. They are:
Inline engines can be found in 2, 3, 4, 5, and 6 cylinder configurations. There have been inline 8 cylinder engines, but they are too long to fit into an engine bay of a conventional modern car.
Cylinders arranged side by side in a single row identify the 'Inline' engine. They can be mounted longitudinally (lengthwise) or transversely (sideways) in the engine bay. However, it is uncommon to find a longer 6-cylinder engine mounted transversely.
"Vee" engines are shorter than an equivalent capacity inline engine. They can be found in 2, 4, 6, 8, 10 and 12 cylinder configurations and consist of two banks of cylinders arranged in a Vee that is joined at the bottom. They are shorter than inline engines, because offsetting the wider top parts of alternate cylinders into the different arms of the Vee allows them to be connected closer together at the crankshaft.
Vee engines can be mounted longitudinally (lengthwise) or transversely (sideways) in the engine bay. A V6 will have two banks of 3 cylinders, a V8 two banks of 4 cylinders.
The angle of the "Vee" varies according to the number of cylinders. The natural angle for a V4 and V8 is 90°. The natural angle for a V6 and V12 is 60° and for a V10 is 72°. Some manufacturers vary their angles due to convenience or design requirements. Some manufacturers use 90° and 15° V6°s
Horizontally opposed engines are commonly found in 2, 4, 6, and 12 cylinder configurations. Like a "Vee" engine, they have two banks, but in this case they are 180° apart. Unlike "Vee" engines their crankshaft differs in the way the pistons are paired. A Horizontally Opposed engine is only fitted longitudinally.
Rotary engines are very powerful for their size, but they do not use conventional pistons that slide back and forth inside a straight cylinder. Instead, a rotary engine uses a rotor which has three convex sides, attached to an eccentric shaft inside a specially shaped housing. As the rotor rotates, it covers and uncovers inlet and exhaust ports, and its curved shape alters the size of the working chambers, which are formed in the spaces between the outside of the rotor and the inside of the housing. For each complete rotation of the rotor, there are three power pulses, and three rotations of the shaft.