LR3/Disco 3
FUEL PUMP RELAY
The V8 engine has a returnless fuel system. The system pressure is maintained at a constant 4 bar (59 Psi), with no
reference to intake manifold pressure. The fuel is supplied to the injectors from a fuel pump fitted within the fuel tank. The
electrical supply to this fuel pump is controlled by the ECM via a relay and an Inertia Switch which will turn the fuel off
upon a vehicle impact. The fuel system is pressurised as soon as the ECM is powered up, the pump is then switched off
until engine start has been achieved.
VISCOUS FAN CONTROL
The ECM controls a viscous coupled fan to provide engine cooling. The ECM supplies the fan with a PWM signal that
controls the amount of slippage of the fan, thus providing the correct amount of cooling fan speed and airflow. The EMS
uses a Hall Effect sensor to determine the fan speed. For additional information, refer to
Engine Cooling
(303-03B
Engine Cooling - 4.4L)
VARIABLE VALVE TIMING (VVT)
Variable valve timing is used on the V8 engine to enhance low and high speed engine performance and idle speed
quality.
For each inlet camshaft the VVT system comprises:
VVT unit
Valve timing solenoid
The VVT system alters the phase of the intake valves relative to the fixed timing of the exhaust valves, to alter:
The mass of air flow to the cylinders.
The engine torque response.
Emissions.
The VVT unit uses a vane type device to control the camshaft angle. The system operates over a range of 48 degrees
and is advanced or retarded to its optimum position within this range.
The VVT system is controlled by the ECM based on engine load and speed along with engine oil temperature to calculate
the appropriate camshaft position.
The VVT system provides the following advantages:
Reduced engine emissions and improved fuel consumption which in turn improves the engines internal EGR effect
over a wider operating range.
Enhanced full load torque characteristics.
Improved fuel economy through optimised torque over the engine speed range.
Variable Valve Timing Unit
