Firing order

The firing order of an internal combustion engine is the sequence of ignition for the cylinders.

Firing order affects the vibration, sound and evenness of power output from the engine and heavily influences crankshaft design.

As a consequence, the left bank of a transversely V engine is usually closest to the front of the car.

Large diesel truck and locomotive engines, particularly of European manufacture, may also be numbered this way.

Moreover, unless there is an odd number of cylinders, the ring cam around the nose of the engine would be unable to provide the inlet valve open - exhaust valve open sequence required by the four-stroke cycle.

To minimise vibrations, most engines use an evenly spaced firing interval.

This means that the timing of the power stroke is evenly spaced between cylinders.