Turbocharger Vane Position Actuator
A 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 Variable Geometry Turbine (VGT) body assembly contains a contact-less inductive VGT position sensing element that is managed by a customized integrated circuit. The VGT position sensor is mounted within the VGT body assembly and is not serviceable. The engine control module (ECM) supplies the VGT body with a 5 V reference circuit, a low reference circuit, an H-bridge motor directional control circuit, and an asynchronous signal/serial data circuit. The asynchronous signal means communication is only going from the VGT body to the ECM. The VGT body cannot receive data from the ECM over the signal/serial data circuit. The VGT position sensor provides a signal voltage that changes relative to VGT vanes angle. The customized integrated circuit translates the voltage based position information into serial data using the Society of Automotive Engineers (SAE) J2716 Single Edge Nibble Transmission (SENT) protocol. The VGT position sensor information is transmitted between the VGT body and the ECM on the signal/serial data circuit. The ECM decodes the serial data signal and is used as voltages for VGT position sensor.
The turbocharger vanes are normally closed at idle, greater than 70%, when the engine is not under load. As the vehicle accelerates and the torque request stabilizes, the ECM will open the turbocharger vanes to regulate boost pressure.
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 maintain a more closed vane position, at low load conditions, in order to accelerate engine coolant heating.