How does a turbocharger work?

A turbo is comprised of two main parts – the compressor side and the turbine side. These are also respectively known as the ‘cold’ side and the ‘hot’ side. These are connected by a shaft, so turning the turbine wheel will turn the compressor wheel.

Exhaust gas from the engine turns the turbine wheel, which in turn via the connected shaft turns the compressor wheel. The compressor wheel compresses fresh oxygenated cool air from the atmosphere. This compression heats the air which if fed directly into the engine could decrease efficiency and cause knocking. This hot compressed air is cooled by passing it through an intercooler – usually an air to air heat exchanger. Cooling the air also increases its density – charge density, so providing volumetric efficiency. This cool, dense, oxygenated air is forced into the engine, providing more efficient combustion, enabling fuel to be burned at an increased rate, and therefore crucially creating more power.

More combustion creates more exhaust gas, which drives the turbine wheel faster, driving the compressor wheel faster, providing more air for combustion, so creating a feedback loop of ever increasing power creation.

Turbochargers can spin at well over 100,000rpm, but every turbo has a maximum limit and cannot spin infinitely faster. A dump valve, also known as a wastegate, diverts excess exhaust gas away from the turbocharger, therefore limiting the rotational speed of the turbine wheel to speeds within the safe operating limits of the turbocharger.

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