Turbocharger Bypass Solenoid Valve (Compressor Recirculation Valve)

The turbocharger bypass valve prevents the turbo from exceeding the surge limit of the compressor at low flow and high pressure. This occurs when the engine is running with a load and the throttle suddenly closes. In this case, flow is almost null and pressure is very high. This not only is damaging to the turbocharger, but also generates noise and decelerates turbine speed.

The turbocharger bypass solenoid valve is mounted to the turbocharger compressor housing. Ignition voltage is supplied to the solenoid valve through a fuse. The ECM commands the solenoid valve On by grounding the control circuit with a solid state device called an output driver. When the solenoid valve is commanded On the spring tension of the valve is overcome and the solenoid valve opens, allowing boost pressure to recirculate through the induction system. When the solenoid valve is commanded Off, at rest, the solenoid valve is spring loaded in the closed position, allowing boost to enter the intake manifold.

Accelerator Pedal Depressed 

The turbocharger bypass solenoid valve is closed. The force in the return spring integrated in the valve presses the valve cone against its seat in the turbo housing. The valve is commanded Off/Closed.

Accelerator Pedal Released 

In order to avoid pressure spikes in the intake manifold and unloading or overrunning the turbo, the ECM commands the turbocharger bypass solenoid valve On/Open. The compressed air on the pressure side of the turbo is led to the intake via the open valve. When the pressure drops, the turbine speed can be kept relatively high and the turbocharger is prevented from exceeding the surge limit of the compressor.