Turbocharger System Description (LLU)
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Turbocharger System Description (LLU)
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Turbocharger Description and Operation
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A turbocharger is a compressor that is used to increase the power output of an engine by increasing the mass of the oxygen and therefore the fuel entering the engine. The turbocharger on this vehicle is mounted on the exhaust manifold and the lightweight turbine is driven by the waste energy generated by the flow of the exhaust gases. The turbine is connected by a shaft to the compressor which is mounted in the induction system of the engine. The compressor vanes compress the intake air above atmospheric pressure, there by greatly increasing the density of the air entering the engine. The turbocharger is capable of producing up to 137 kPa (20 PSI) or 1.40 bar, of power enhancing boost.
The turbocharger incorporates a wastegate that is controlled by a pressure differential, that is determined by the engine control module (ECM) by means of a pulse width modulation (PWM) solenoid, in order to regulate the pressure ratio of the compressor. A charge air bypass valve also controlled by the ECM by utilizing a remotely mounted solenoid is integrated into the bypass valve to prevent compressor surging and damage from vibrations by opening during abrupt closed throttle conditions. When the bypass valve is open during closed throttle deceleration conditions, the bypass valve allows the air to recirculate in the turbocharger and maintain compressor speed. Within a calibrated range during the closed throttle event, or upon a wide open throttle command the bypass valve will then close to optimize turbo response.
The turbocharger connects to the engine's oil system via a feed line and a return line. Mobil 1™ synthetic oil is used from the factory. Synthetic oil is required for its friction reducing capabilities and high temperature performance. There is a cooling system circuit in the turbocharger that utilizes the engine coolant to further reduce operating temperatures.
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Turbocharger Pressure Sensor
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The turbocharger boost pressure sensor is mounted on the intake manifold and measures boost pressure and air temperature. The boost pressure sensor also has an intake air temperature sensor 2 which is integrated within the boost pressure sensor.
The turbocharger is fed by an air-to-air charge air cooler system. This uses fresh air which is led through a heat exchanger to reduce the temperature of the warmer compressed air introduced through the induction system. Inlet air temperature can be reduced by up to 100°C (180°F), enhancing performance because cooler air is denser in oxygen and promotes optimal combustion. The change air cooler is connected to the turbocharger and to the throttle body by flexible duct work that requires the use of special high torque fastening clamps. In order to prevent any type of air leak when servicing the duct work, the tightening specifications and proper positioning of the clamps is critical, and must be strictly adhered to.
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Engine Control Module (ECM)
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The engine control module (ECM) controls all turbocharger control functions. The ECM monitors information from various sensor inputs that include the following:
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The accelerator pedal position (APP) sensor
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The engine coolant temperature (ECT) sensor
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The mass air flow (MAF) sensor
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The intake air temperature (IAT) sensor 2
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The vehicle speed sensor (VSS)
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The boost pressure sensor
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Recommendations for Service
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The turbocharger is designed so that it does not require any special maintenance, and inspection is limited to a few periodic procedures. To ensure that the turbochargers lifetime corresponds to that of the engine, the following engine manufacturers service instructions must be strictly adhered to:
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Oil and filter change intervals
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Maintaining the proper oil pressure
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Air filter change intervals
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Engine coolant change intervals
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Ignition system maintenance
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Injection system maintenance
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The following causes are responsible for 90% of all turbocharger failures:
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Penetration of foreign bodies into the turbine or the compressor
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Dirt or contaminants in the oil
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Inadequate oil supply and/or pressure
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Higher than normal exhaust gas temperatures due to improper operation of the following:
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The fuel injection system
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These failures can be avoided by regular maintenance.
