Turbocharger Wastegate Solenoid Valve

WARNING: This page is about a different variant/trim than selected.

The wastegate valve opens and closes a bypass passage beside the turbine wheel. A spiral spring works in the opening direction while vacuum in the diaphragm works in the closing direction. The ECM supplies a PWM signal to the solenoid valve, which then allows vacuum to come through. When the vacuum overcomes the spring force the actuator rod begins to move, closing the wastegate valve to a corresponding degree. The ECM changes wastegate valve opening by varying the PWM signal, which regulates the turbine speed.

At low loads, the wastegate valve is closed. All the exhaust gas then passes through the turbine. At high loads, the volume of exhaust gas is greater, which makes the turbine wheel rotate faster. This delivers a greater air displacement to the engine.

When the air displacement becomes so large that the current air mass per combustion cannot be controlled with the throttle alone, the turbo must be regulated. This is done by opening the wastegate valve so that some of the exhaust gas passes through the wastegate. Consequently, this gas does not contribute to driving the turbine and the turbine speed will be regulated so that the turbo air displacement will be correct.

Wastegate Solenoid Valve 95 to 100 % duty cycle = 95 to 100 % of the vacuum source is routed to the wastegate actuator. 0 to 5 % of the vacuum source is routed to the air inlet duct. = Full boost
Wastegate Solenoid Valve 0 to 5 % duty cycle = 0 to 5 % of the vacuum source is routed to the wastegate actuator. 95 to 100 % of the vacuum source is routed to the air inlet duct. = No boost
Wastegate Solenoid Valve 5 to 95 % duty cycle = Any amount from 5 to 95% of the vacuum source is routed to the air inlet duct. The difference is routed to the wastegate actuator. = Boost Control

When certain DTCs are set the ECM will limit the amount of available boost pressure. Limiting boost pressure is accomplished by the ECM controlling the wastegate actuator solenoid valve and maintaining the duty cycle at 0 %. This means that the ECM will not actively close the wastegate during greater engine loads. The system at this point is limited to mechanical boost. This is the boost pressure the system will create with the wastegate fully open. When a DTC is set, the solenoid feeds little to no vacuum to the wastegate, allowing it to reach full (or nearly full) open position. This limits the boost pressure by allowing as much flow as possible to pass through the wastegate valve, this boost pressure is very close to atmospheric pressure under almost all driving conditions.

The turbocharger wastegate diaphragm valve assembly has a threaded rod and nut that connects the diaphragm of the valve to the wastegate.

The following diagrams illustrate the turbocharger wastegate closed and open conditions: