Solenoid, WASTEGATE: Description
The base turbocharger boost pressure is managed by the mechanical wastegate. The wastegate is a spring loaded mechanical valve that is normally open, allowing the exhaust gases to bypass the turbine inside the turbocharger. When the Powertrain Control Module (PCM) decides to allow boost, it energizes the wastegate solenoid (1), allowing boost pressure to be applied to a diaphragm that works against the spring pressure of the wastegate.
The boost pressure is supplied to the wastegate solenoid through a hose connected to the compressor side of the turbocharger. The boost pressure is low at lower engine speeds and increases as engine speed increases. The increase in boost pressure with engine speed controls the rate that the wastegate opens. As the boost pressure increases and closes the wastegate, it allows more of the exhaust gases to be directed through the turbine, increasing the turbine speed and amount of boost by the turbocharger.
The Powertrain Control Module (PCM) controls the wastegate solenoid through a Low Side Driver (LSD) circuit which uses vacuum to control the pneumatic wastegate valve actuator to manage its motion. When energized by the PCM, the wastegate solenoid allows boost pressure from the turbocharger compressor to act on the diaphragm connected to the wastegate.