Turbocharger - Gasoline: Operation: Notes

The turbine wheel is driven by exhaust gases. A shaft connects the turbine wheel with the compressor wheel. As exhaust gas flow increases with engine speed, the turbine speed increases and compressor discharge increases.

Turbocharger wheels rotate at high speed, requiring the shaft assembly to be carefully balanced. The shaft is supported by bearings using pressurized oil for lubrication. The shaft seals are a piston ring type.

Turbocharger lubrication is supplied by the engine oiling system. Oil supply and pressure must be sufficient to prevent shaft bearing failure. The turbocharger is designed to provide a relatively high discharge pressure at mid-range RPM. In order to prevent excessive pressure at high speeds, several controlling and regulating devices are required.