3000GT AWD V6-2972cc 3.0L DOHC Turbo (1991)
Wastegate Solenoid: Description and Operation
Wastegate Control Solenoid Circuit
The wastegate control solenoid is located on the center of the firewall. It is an on off type duty cycle solenoid, that is used to regulate the turbo boost
pressure from about 8 to 12 PSI, by controlling 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.
