Wastegate Solenoid: Description and Operation

Waste Gate Solenoid Control Circuit:

The wastegate control solenoid is located next to the air filter housing. It is an on off type solenoid, that is used to regulate the turbo boost pressure from about 8 to 12 PSI, by controling the amount of overboost pressure fed to the wastegate actuator. This is to maintain the optimum boost pressure under all driving conditions. The wastegate actuator is set to open with a minimum of boost pressure, this is to prevent damage to the engine if the solenoid becomes inoperable.

The ECU uses vehicle load condition inputs from the detonation sensor and the air flow sensor to regulate the on off signal to the solenoid. The wastegate solenoid is spring loaded in the closed (lowest boost) position until after the engine is started. It then will fully ground the circuit (highest boost) and leave it grounded while the engine is running.

When the solenoid is energized, the wastegate actuator pressure is purged back to the air filter housing and keeps the wastegate closed. The solenoid is powered by the control relay, the ground is provided by the E.C.U. The E.C.U. controls the solenoid operation by switching the ground on and off according to boost pressure. The boost pressure is calculated by the E.C.U. based on inputs from the air flow meter, detonation sensor, engine RPM, barometric pressure sensor and the intake air temperature sensor

The ECU does not control boost pressure it only regulates it during failures of the control components. The wastegate valve allows the excess pressure to bypass the turbine blades.