A supercharger powered by an exhaust-driven turbine. Turbochargers always use centrifugal-flow compressors, which operate efficiently at the high rotational speeds produced by the exhaust turbine.

The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally-aspirated engine, which allows more fuel to be provided and more work to be done per cycle, increasing power output.

Boost Pressure

The increase above atmospheric pressure produced inside the intake manifold by a forced-induction system such as a turbocharger or supercharger. Boost is commonly measured in psi.

Compressor Wheel

The wheel on a turbocharge which pulls air and forces into the engine.

Dump Valve

A valve to vent off turbo pressurised air when the throttle is closed on gearchanges, to prevent the turbo stalling.


Another name for a turbo′s compressor wheel.


The wheel on a turbo which is driven by the exhaust gas.

Turbo Lag

Within a turbocharger's operating range, lag is the delay between the instant a car's accelerator is depressed and the time the turbocharged engine develops a large fraction of the power available at that point in the engine's power curve.

Waste Gate

A valve used to limit the boost developed in a turbocharger. A waste gate operates by allowing some of the engine's exhaust flow to bypass the turbocharger's turbine section under certain conditions.

See also: Centrifugal Fan, Compressor, Exhaust Downpipe, Impeller, Intercooler, Internal Combustion Engine, Naturally Aspirated, Normally Aspirated Engine, Supercharger, Turbo Lag.

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Subjects: Engines