The firing order is the sequence of power delivery of each cylinder in a multi-cylinder reciprocating engine

Reciprocating engine

A reciprocating engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types...

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This is achieved by sparking of the spark plug

Spark plug

A spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed fuels such as aerosol, gasoline, ethanol, and liquefied petroleum gas by means of an electric spark.Spark plugs have an insulated central electrode which is connected by...

s in a gasoline engine in the correct order, or by the sequence of fuel injection in a Diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

. When designing an engine, choosing an appropriate firing order is critical to minimizing vibration

Oscillation

Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...

 and achieving smooth running, for long engine fatigue

Metal Fatigue

Metal Fatigue , is a futuristic science fiction, real-time strategy computer game developed by Zono Incorporated and published by Psygnosis and TalonSoft .-Plot:...

 life and user comfort, and heavily influences crankshaft design.

In a gasoline engine, the correct firing order is obtained by the correct placement of the spark plug wires on the distributor

Distributor

A distributor is a device in the ignition system of an internal combustion engine that routes high voltage from the ignition coil to the spark plugs in the correct firing order. The first reliable battery operated ignition was developed by Dayton Engineering Laboratories Co. and introduced in the...

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