Circuit/System Description

The turbocharger increases engine power by pumping compressed air into the combustion chambers, allowing a greater quantity of fuel to combust at the optimal air/fuel ratio. The turbine spins as exhaust gas flows out of the engine and over the turbine blades, and turns the compress or wheel at the other end of the turbine shaft, pumping more air into the intake system.

The engine control module (ECM) controls the vanes of variable geometry turbine. The vanes are used to vary the amount of boost pressure and can control the boost pressure independent of engine speed. The vanes mount to the compress or unison ring of turbocharger, which is rotated to change the vane angle. The ECM will vary the vane angle which adjusts boost depending on the load requirements of the engine.

The turbocharger vanes are normally open when the engine is not under load. However, the ECM will often close the turbocharger vanes to create back pressure to drive exhaust gas through the exhaust gas recirculation (EGR) valve as required. At extreme cold temperatures, the ECM may close the vanes at low load conditions in order to accelerate engine coolant heating.

The variable geometry turbine assembly contains a contact-less inductive position sensing element that is managed by a customized integrated circuit. The variable geometry position sensor is mounted within the turbocharger assembly and is not serviceable. The ECM supplies the variable geometry turbine assembly with a 5V reference circuit, a low reference circuit, an H-bridge motor directional control circuit, and an asynchronous signal/serial data circuit.