Circuit/System Description

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.

The boost pressure sensor is integrated with the turbocharger boost/intake air temperature sensor. The boost pressure sensor measures the range of pressures between the turbocharger and the throttle body. The sensor used on this engine is a three atmosphere sensor. Pressure in this portion of the induction system is affected by engine speed, throttle opening, turbocharger boost pressure, intake air temperature (IAT), barometric pressure (BARO), and the efficiency of the charge air cooler.

The sensor provides a signal voltage to the engine control module (ECM), relative to the pressure changes. Under normal operation the greatest pressure that can exist in this portion of the induction system at ignition ON, engine OFF is equal to the BARO. When the engine is operated at wide-open throttle (WOT) the turbocharger can increase the pressure to near 240 kPa (34.8 psi). The pressure is equal to the BARO when the engine is idling or decelerating.

The turbochargers each incorporate a vacuum operated wastegate that is controlled by the engine control module (ECM) by means of a remotely mounted solenoid, to regulate the pressure ratio of the compressor. The wastegate valve vacuum source is provided by a vacuum pump which is driven off the end of the right hand exhaust camshaft.

At idle the turbocharger wastegate solenoids are open. When the engine load and RPM increase under a wide open throttle, the turbocharger wastegate valves close to increase boost pressure. When the proper level of boost pressure is attained, the ECM will partially open the wastegates to maintain the boost pressure level. When the throttle closes, the ECM commands the wastegates to open to reduce the speed of the turbines.