Turbocharger System Description (LLU)
Turbocharger Description and Operation
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 is connected to the engine oiling system by a
supply and drain tube and Mobil 1™ synthetic oil is installed
at 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.
Turbocharger Pressure Sensor
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 Charged Air Cooler
The turbocharger is supported by an air to air charge air cooler
system, which uses fresh air drawn through a heat exchanger to
reduce the temperature of the warmer compressed air forced through
the intake 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.
Engine Control Module (ECM)
The engine control module (ECM) controls all turbocharger
control functions. The ECM monitors information from various sensor
inputs that include the following:
• |
The accelerator pedal position
(APP) sensor |
• |
The engine coolant temperature
(ECT) sensor |
• |
The mass air flow (MAF)
sensor |
• |
The intake air temperature
(IAT) sensor 2 |
• |
The vehicle speed sensor
(VSS) |
• |
The boost pressure
sensor |
Recommendations for Service
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:
• |
Oil and filter change
intervals |
• |
Maintaining the proper oil
pressure |
• |
Air filter change
intervals |
• |
Engine coolant change
intervals |
• |
Ignition system
maintenance |
• |
Injection system
maintenance |
The following causes are responsible for 90% of all turbocharger
failures:
• |
Penetration of foreign bodies
into the turbine or the compressor |
• |
Dirt or contaminants in the
oil |
• |
Inadequate oil supply and/or
pressure |
• |
Higher than normal exhaust gas
temperatures due to improper operation of the following:
|
|
- |
The fuel
injection system |
These failures can be avoided by regular maintenance.
|