Jaguar AJV8 engine / 5HP24 transmission. Instruction - page 6

Engine

AJ-V8/5HP24

25

Bush Carrier

The bush carrier contains oil passages that link
the engine oil supply to the valve timing unit. A
lug on the bush carrier locates in the central bore
of the valve timing unit. Two hollow dowels at
the bush carrier to cylinder block interface ensure
the lug is accurately located. A scarf- jointed fibre
ring seals the joint between the lug and the valve
timing unit. An integral shuttle valve, biased by a
coil spring, controls the flow of oil through the oil
passages.

VALVE TIMING UNIT

BUSH CARRIERS

Inner
Sleeve

Return
Spring

Piston

Ring Gears

Body and Sprocket
Assembly

303-002

303-003

Engine

AJ-V8/5HP24

26

Valve Timing Solenoid

The valve timing solenoid controls the position of
the shuttle valve in the bush carrier. A plunger on
the solenoid extends when the solenoid is
energised and retracts when the solenoid is de-
energised.

Operation

When the valve timing solenoids are de-
energised, the coil springs in the bush carriers
position the shuttle valves to connect the valve
timing units to drain. In the valve timing units, the
return springs hold the ring pistons and gears in
the retarded position.
When the valve timing solenoids are energised
by the ECM, the solenoid plungers position the
shuttle valves to direct engine oil to the valve
timing units. In the valve timing units, the oil
pressure overcomes the force of the return
springs and moves the gears and ring pistons to
the advanced position.
System response times are 1.0 second maximum
for advancing and 0.7 second maximum for
retarding.
While the valve timing is in the retarded mode,
the ECM produces a periodic lubrication pulse.

VALVE TIMING SOLENOID

VARIABLE VALVE TIMING OPERATION

Retarded

Advanced

Engine Oil Pressure

303-004

Engine Oil Pressure

303-005

Engine

AJ-V8/5HP24

27

This momentarily energises the valve timing
solenoids to allow a spurt of oil into the valve
timing units. The lubrication pulse occurs once
every 5 minutes.

Note:

With the vehicle stationary and the hood
open, operation of the valve timing
solenoids may be audible when the
lubrication pulse occurs at engine idle
speed.

Air Intake System

Filtered air from the vehicle's intake ducting is
metered by the electronic throttle then directed
through the induction elbow into the intake
manifold.

AIR INTAKE SYSTEM

Intake
Manifold

Electronic
Throttle

Induction
Elbow

303-050

Engine

AJ-V8/5HP24

28

Electronic Throttle

The electronic throttle enables the ECM to
control the flow of air into the engine. It includes:

an input shaft that receives driver inputs from
the accelerator pedal via a conventional
throttle cable

a mechanical guard, to prevent throttle valve
position exceeding driver demand and to
operate the throttle valve mechanically if the
electronic system fails

a vacuum actuator, to operate the mechanical
guard in the cruise control mode of operation

a throttle valve, to regulate the air flow

a thermostatic air valve, to control a bypass
flow around the throttle valve

a dc motor, to operate the throttle valve in
response to inputs from the ECM

three position sensors, to supply the ECM
with the position's of the input shaft (ie.
accelerator pedal), the mechanical guard and
the throttle valve

springs connected to the input shaft, the
mechanical guard, the throttle valve and the
drive gear of the dc motor.

Vacuum Actuator

On vehicles with cruise control, the vacuum
actuator is connected to manifold vacuum and
controlled by the ECM. On vehicles without
cruise control, the vacuum actuator is open to
atmosphere and the actuator is inoperative.

Thermostatic Air Valve

The thermostatic air valve is a wax capsule
operated valve that enables engine starting at
low engine temperatures (with the accelerator
pedal in the idle position, the degree of throttle
valve movement available between fully closed
and the mechanical guard is insufficient to start
the engine at low temperatures). The
thermostatic air valve is fully open at a coolant
temperature of approximately -30°C (-22˚F) and
progressively closes until it is fully closed at
+40 °C (+104˚F). A flow of engine coolant
through the throttle body provides the
temperature source to operate the thermostatic
air valve.

SIMPLIFIED VIEW OF ELECTRONIC THROTTLE

Throttle Valve
Position Sensor

Mechanical Guard

Mechanical Guard
Position Sensor

Accelerator Pedal
Position Sensor

Input
Shaft

303-080

Spring Force

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