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.

Each of the turbochargers is provided with a vacuum operated bypass valve, which opens during abrupt closed throttle conditions, to prevent turbocharger surging and damage from vibrations. The bypass valve vacuum source is provided by a vacuum pump which is driven off the end of the right hand exhaust camshaft. The valves are controlled by the engine control module (ECM), by utilizing remotely mounted solenoid valves. When the valves open during closed throttle deceleration conditions, air is allowed to recirculate in the turbochargers to maintain turbocharger speed. Within a calibrated range during a closed throttle event, or upon a wide open throttle command the valves close to optimize turbo response.

As engine load and engine speed increases, the turbocharger bypass solenoid valves are commanded ON by the ECM. As soon as the throttle closes the turbocharger bypass solenoid valves are commanded OFF by the ECM to allow the bypass valves to open and allow the turbocharger air to recirculate to prevent surging.