LR3/Disco 3
the end of the drive shaft; this feedback signal is used to determine the angular position of the vanes. This information is
transmitted to the Engine Control Module (ECM).
There is a temperature sensor in the control unit, which drives the stepper motor to a safe position (vanes fully opened) if
the maximum temperature is exceeded. The ECM detects any malfunctions in the stepper motor and generates
Diagnostic Trouble Codes (DTC).
At low engine speeds, because of the flat setting of the vanes, the relatively low flow of exhaust gases are accelerated
and routed in such a way that they meet the vanes of the turbine wheel at the outermost edge. Consequently, a high
torque is produced at the turbine wheel, and a high turbine speed is therefore achieved.
At high engine speeds the vanes are progressively opened, so that a large flow of exhaust gas is delayed and is directed
more and more towards the centre of the turbine wheel.
The torque at the turbine wheel is artificially lowered. In this way the turbine speed, and therefore the air quantity required
by the engine, are matched to engine speed. Consequently, the boost pressure is approximately constant over the whole
engine speed range.
The operating parameters are controlled electronically by the ECM using powertrain sensors and driver inputs. For
additional information, refer to
Electronic Engine Controls
(303-14C Electronic Engine Controls - 2.7L Diesel)
The turbocharger is designed for fail safe operation. If a fault occurs regarding the control of the unit, the vanes default to
the fully open position so as to produce minimum boost.
Item Part Number
Description
A
-
Closed (fast)
B
-
Open (slow), default position
1
-
Turbine
2
-
Vanes
3
Actuator lever
