Wastegate: Description and Operation

PURPOSE/OPERATION
The wastegate actuator 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 is spring loaded in the closed (highest boost) position. Under normal operating conditions the wastegate is controlled directly by boost pressure. As boost pressure rises (on the throttle side of the throttle valve), the pressure against the diaphragm overcomes the spring pressure holding the wastegate closed. As the wastegate is forced open it vents exhaust (drive) pressure around the drive turbine. This limits the maximum pressure that the turbocharger can build in the intake system.