Wastegate Actuator: Description and Operation

Turbocharger Components:

PURPOSE
The Wastegate Actuator prevents charge air pressure building too high. Each turbocharger has it's own wastegate and actuator.

DESCRIPTION
The Wastegate Actuator Valve (item #2) is a boost pressure operated device, that opens and closes the internally mounted bypass valve (wastegate) in the exhaust turbine housing of the Turbocharger. The Wastegate Actuator Valve has two separate chambers. The actuator valve is spring loaded in the closed (highest boost) position.

OPERATION
The top chamber is open to manifold boost pressure (from above the throttle plate) all the time. The lower chamber is controlled through the wastegate solenoid valve by the Engine Control Module (ECM).

In the lowest boost condition the solenoid valve applies boost pressure to the lower chamber the same as to the top chamber, to assist the top chamber in opening the wastegate.

In the higher boost condition the solenoid valve applies vacuum from the air inlet side of the turbocharger to the lower chamber. This requires that the boost rise to a higher pressure before the single (top chamber) diaphragm can force open the wastegate.