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. In a conventional turbo, the turbine (4) spins as exhaust gas flows out of the engine and over the turbine blades. This spins the compressor wheel at the other end of the turbine shaft, pumping more air into the intake system.

The turbocharger for this system has vane position control by the engine control module (ECM). The vanes (5) are controlled to vary the amount of boost pressure. Thus, the boost pressure can be controlled independent of engine speed. There are 9 controllable vanes in this turbocharger. The vanes mount to a unison ring (3) that can be rotated to change the vane angle. The ECM will vary the boost dependent upon 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 ECM may also close the turbocharger vanes under exhaust braking conditions, only with RPO K40.

The turbocharger control system utilizes the following components:

The vane position control solenoid valve (2) works in conjunction with oil pressure to control the turbocharger vanes. The solenoid valve has two circuits; a low control circuit and a high control circuit. The engine control module (ECM) uses a pulse width modulation on both control circuits to control the solenoid valve. The ECM will control the solenoid valve to allow the engine oil pressure (EOP) to move a piston (6). This piston rotates the unison ring, thus controlling the engine boost dependant upon engine load.

The vane position sensor (1) uses 3 circuits: a 5-volt reference circuit, a low reference circuit, and a signal circuit. The engine control module (ECM) provides the sensor with 5 volts on the 5-volt reference circuit and a ground on the low reference circuit. Movement of the vanes provides the ECM with a signal voltage from the TC sensor through the position sensor signal circuit. The voltage is low when the TC vanes are open, and high when the TC vanes are closed.

The engine control module (ECM) controls all turbocharger control functions. The ECM monitors information from various sensor inputs that include the following: