Circuit/System Description

WARNING: This page is about a different car, the 2010 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.

The BorgWarner™ dual-scroll turbocharger incorporates a wastegate that is controlled by a pressure differential, that is determined by the engine control module (ECM) by means of a PWM solenoid, in order to regulate the pressure ratio of the compressor. A compressor bypass valve also controlled by the ECM by utilizing a remotely mounted solenoid is integrated into the unit to prevent compressor surging and damage from vibrations by opening during abrupt closed throttle conditions. When the valve is open during closed throttle deceleration conditions, the bypass valve allows the air to recirculate in the turbocharger and maintain compressor speed. Within a calibrated range during the closed throttle event, or upon a wide open throttle command the valve will then close to optimize turbo response. The bypass valve solenoid has the following circuits:

Ignition voltage
Turbocharger bypass valve solenoid control

As engine load and RPM increases the Turbocharger Bypass Solenoid parameter should remain commanded ON by the ECM. As soon as the throttle closes the Turbocharger Bypass Solenoid parameter should be commanded OFF by the ECM, in order to allow the turbocharger bypass valve to open and allow the turbocharger air to recirculate, thereby preventing compressor surging.