Engine Performance: System: Turbocharger: Operation: Notes

Turbine impeller of turbocharger is driven by exhaust gases expelled from cylinder combustion chambers. At idle, no pressurization of intake air takes place and engine operates like a normally aspirated engine.

With engine under partial load, throttle valve opens and more air/fuel mixture is drawn into combustion chambers. Speed and volume of exhaust gases also increase, which turns turbine impeller at a higher RPM. Increased RPM of compressor impeller boosts pressure of intake air.

With engine under full load, exhaust gases are at maximum pressure and increase RPM of turbine and compressor impellers to an extremely high speed; boost pressure of intake air then reaches a maximum.

When pressure in intake manifold reaches 8.4 psi (.59 kg/cm² ), diaphragm of wastegate controller pushes against linkage which opens wastegate. Some exhaust gases are then routed directly into main exhaust pipe, by-passing turbine impeller. This prevents engine damage from excessive pressure.