In contrast to conventional naturally aspirated engines, exhaust turbochargers (ETC) use the energy from exhaust gases to charge internal combustion engines. Here, the so-called exhaust turbine takes the energy from the exhaust gas and delivers it to a compressor, which compresses the combustion air, supplies it to the engine and thus produces propulsion. There is no mechanical coupling to the engine. The benefit that this type of charging process delivers is the larger air mass that is supplied to the combustion chamber and that as a result makes it possible to burn more fuel. This produces greater engine performances than those that can be achieved by naturally aspirated engines while at the same time lowering fuel consumption and reducing emissions.
Turbochargers also enable downsizing which makes it possible to realise efficiency increases. Downsizing is when an internal combustion engine's cubic capacity is reduced, while the specific cubic-capacity performance is at the same time increased to such an extent that the downsized engine delivers approximately the same performance as an engine with greater cubic capacity. Downsizing has the benefit of reducing fuel consumption and CO2 emissions. This is achieved by operating engines at greater mean pressures in specifically higher charged and therefore more fuel-efficient engine-map ranges.