Air Induction
Air is drawn through air cleaner and forced through throttle body by turbocharger. Wastegate is controlled by logic module and can increase turbo boost to high levels for brief periods of time. Amount of air entering engine is controlled by cable operated throttle valve in throttle body.
Throttle body houses Throttle Position Sensor (TPS) and Automatic Idle Speed (AIS) motor. TPS is electrical resistor, connected to throttle valve, that signals logic module of changes in throttle valve angle. Logic module then calculates duration of fuel injector pulse (dwell) to provide adequate air/fuel mixture.
AIS motor controls flow of air through by-pass passage in throttle body to increase or decrease idle speed as engine load varies. Engine dying during deceleration is also controlled by AIS motor. Motor increases idle speed whenever throttle closes quickly after driving at speed. Logic module monitors AIS motor and issues change command to injectors to increase or decrease amount of fuel injected.