supercharger

is a device utilizing a blower or pump to provide air to the intake manifold of an internal combustion engine at pressures above atmospheric. Supercharging provides a greater air charge to the cylinders at high crankshaft speeds and at high altitudes, thereby boosting engine power without increasing engine size. Because supercharging maintains maximum intake charge, it offers particular advantages at high altitudes, where the atmosphere contains less oxygen. Some supercharger systems utilize aftercooling to further increase the density of the charge. The blower may be geared to the crankshaft or, in the case of the turbocharger, it may consist of a turbine driven by the exhaust gases to operate the centrifugal blower.

Also see volumetric efficiency.

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