Boost Control Description and Operation: Notes

A turbocharger is a compressor that is used to increase the power output of an engine by increasing the mass of the oxygen and therefore the fuel entering the engine. The turbocharger on this vehicle is mounted on the exhaust manifold and the lightweight turbine is driven by the waste energy generated by the flow of the exhaust gases. The turbine is connected by a shaft to the compressor which is mounted in the induction system of the engine. The compressor vanes compress the intake air above atmospheric pressure, there by greatly increasing the density of the air entering the engine. The turbocharger is capable of producing up to 137 kPa (20 PSI) or 1.40 bar, of power enhancing boost.

The turbocharger incorporates a wastegate that is controlled by a pressure differential, that is determined by the engine control module (ECM) by means of a pulse width modulation (PWM) solenoid, in order to regulate the pressure ratio of the compressor. A charge air bypass valve also controlled by the ECM by utilizing a remotely mounted solenoid is integrated into the charge air bypass valve to prevent compressor surging and damage from vibrations by opening during abrupt closed throttle conditions. When the bypass 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 bypass valve will then close to optimize turbo response.