Frelander 2. Manual — part 257
The REA is directly controlled by the Engine Control Module (ECM). The ECM constantly controls the position of the actuator
using input information from various engine and vehicle mounted sensors. A feed back sensor within the REA continuously
informs the ECM of the actuator position during turbocharger operation. In the event that the variable vanes fail to reach
the requested position, a Diagnostic Trouble Code (DTC) is stored in the ECM memory.
PRINCIPLES OF OPERATION
The turbocharger uses the energy of the exhaust gas flow from the engine to provide compressed (charged) air to the
intake air system. The variable geometry vanes make sure the turbocharger produces the required level of intake air boost
pressure for the current engine operating conditions.
The turbocharged engine provides the following advantages over a conventional naturally aspirated engine:
Greater volumetric efficiency
Improved engine power and torque
Reduced fuel consumption
Reduced emissions
Re-use of exhaust gas energy
Un-affected by altitude
Limited periods of over-boost for immediate engine demands.
Typical Rotary Electronic Actuated Turbocharger
Item
Part Number
Description
A
-
Low engine speed
B
-
Moderate engine speed
C
-
Maximum engine speed
1
-
ECM
2
-
Rotary Electronic Actuator
3
-
Rotary adjusting ring
4
-
Variable vanes
5
-
Turbine wheel
In response to signals from various sensors, the ECM controls the REA to operate the rotary adjusting ring. Movement of
the adjusting ring alters the pitch angle of the variable vanes to deflect the flow of exhaust gas onto the inside center or
outside edge of the turbine wheel.
The maximum position of the turbocharger variable vanes (fully open) is also the emergency default position in the event
of an electrical fault. The REA will move the variable vanes to the fully open position to prevent engine damage due to
excessive boost pressure.
A - Low Engine Speed
At low engine speed the volume of exhaust gas leaving the engine is low. The vanes are moved toward the closed position
to direct the exhaust gas flow to the outside edge of the turbine wheel. The closed position of the vanes creates a
restriction to the gas flow and increases the gas velocity to the turbine wheel. The turbine wheel speed is increased,
consequently producing more charge air (boost pressure) from the compressor.
B - Moderate Engine Speed
As engine speed and exhaust gas volume increase, the vanes are moved to the open position to direct the exhaust gas
flow toward the center of the turbine wheel. The vanes do not restrict the exhaust gas flow and therefore exhaust gas
velocity is dependant on engine speed. The turbine wheel speed is maintained due to the increased velocity of the gases
leaving the engine and being directed toward the center area of the turbine wheel.
C - Maximum Engine Speed
At maximum engine speed the volume of exhaust gas leaving the engine is high. The vanes are moved toward the fully
open position and do not affect the gas velocity. The exhaust gas flow contacts the center area of the turbine wheel to
maintain the turbine wheel speed and boost pressure from the compressor.
Over-Boost Pressure
During periods of medium to hard acceleration, the turbocharger is required to produce a limited period of over-boost
pressure from the compressor to meet the current engine fueling requirement. The ECM will request and allow the REA to
move the variable vanes toward the closed position to increase the velocity of the already high-speed turbine wheel. The
over-boost condition is allowed by the ECM for the limited period.
Barometric Pressure Sensor
At high altitude the turbocharger will function normally, but due to the lower ambient air pressure the turbine and
compressor may tend to over-speed. A barometric pressure sensor is located in the ECM to prevent over-boost and
possible engine damage occurring under these conditions. The ECM opens the variable vanes earlier during the opening
phase to suit the altitude of the vehicle.
Turbocharger Lubrication
The rapid acceleration and deceleration demands of the turbocharger rely on a steady flow of clean oil. The oil supplied by
the engine lubrication system provides lubrication to the turbocharger shaft and bearings, while also acting as a coolant
for the turbocharger center housing.
To maintain the life expectancy of the turbocharger, the engine oil must be replenished at regular service intervals with
the recommended quality and quantity of oil. The oil must have a free-flow through the turbocharger and an unrestricted
return to the engine oil pan.
Fuel Charging and Controls - Turbocharger - TD4 2.2L Diesel - Turbocharger
Actuator Rod
Removal and Installation
Removal
• NOTE: Removal steps in this procedure may contain installation details.
• NOTE: Some variation in the illustrations may occur, but the essential information is always correct.
1.
WARNING: Do not work on or under a vehicle supported only
by a jack. Always support the vehicle on safety stands.
Raise and support the vehicle.
1.
Torque: 25 Nm
2.
3. NOTE: Vehicles fitted with diesel particulate filter
(DPF)
3.
4. NOTE: Note the position of the hoses.
4.
5.
6. NOTE: All vehicles.
Torque: 10 Nm
6.
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