Forced induction

In an internal combustion engine, forced induction is where turbocharging or supercharging is used to increase the density of the intake air.

[2] This is achieved by compressing the intake air, to increase the mass of the air-fuel mixture present within the combustion chamber.

A naturally aspirated engine is limited to a maximum intake air pressure equal to its surrounding atmosphere; however a forced induction engine produces "boost",[3] whereby the air pressure is higher than the surrounding atmosphere.

Four-stroke diesel engines are well suited to forced induction, since the lack of fuel in the intake air means that higher compression ratios can be used without a risk of pre-ignition.

[5] Forced induction is used to artificially increase the density of the intake air, in order to reduce the loss of power at higher altitudes.

A turbocharger for a car engine
A supercharger (on top of a dark-grey inlet manifold) for a car engine