JAGUAR S TYPE 1999 1.G Powertrain Manual

V6 Engine AJ-V6/AJ28
16
Crankcase Ventilation
Full Load Ventilation
Breather outlets on each cam cover are connected
via hoses and a Tee junction to the intake duct to
provide full load crankcase ventilation.
Positive Crankcase Ventilation
Under closed or near closed throttle conditions,
engine breathing is mainly via the positive
crankcase ventilation (PCV) system. An oil
separator is bolted to the top of the engine block
between the cylinder banks and has an outlet
connected to the intake manifold via an in-line
PCV valve and hoses. The PCV valve has a spring
J.303.1286
FULL LOAD VENTILATION
D.303.1286
loaded plunger which opens under the intake
vacuum created at low throttle openings. When
the PCV valve is open, crankcase gases are drawn
through the separator, depositing oil droplets on
an internal baffle for return to the sump.
The PCV inlet tube to the manifold is heated by
the engine cooling system.
J.303.1290
POSITIVE CRANKCASE VENTILATION
D.303.1290
Oil Separator
PCV valve

V6 EngineAJ-V6/AJ28
17
Exhaust Gas Re-circulation (EGR)
Operation
The EGR system is only fitted to vehicles in NAS
markets and comprises the following
components:
¥ EGR vacuum regulator valve
¥ EGR valve
¥ differential pressure feedback EGR sensor
¥ exhaust gas feedback pipe with internal
orifice
Exhaust gas is re-circulated back to the engine
intake in proportion to a measured pressure
differential in the feedback pipe. The amount of
gas re-circulated varies primarily with engine
speed and load but is also modified by the EMS to
allow for other factors, eg coolant temperature,
and also to achieve optimum emissions and fuel
economy.
The re-circulated exhaust gas is taken from the A
bank exhaust manifold and fed into the engine via
the EGR valve. The feedback pipe contains an
internal tube with a small diameter orifice that
creates a pressure differential in the feedback
pipe. Two small pipes, connected to the feedbackpipe each side of the orifice, transmit the pressure
differential to the differential pressure feedback
EGR sensor.
The sensor consists of a transducer (a vacuum
operated variable capacitor) and a processing
circuit which convert the input pressure/vacuum
value to a corresponding analogue voltage which is
sent to the PCM. The differential pressure feedback
EGR sensor has a linear response and the
variations in exhaust pressure produce outputs in
the approximate range 1V- 3.5V dc.
The EGR vacuum regulator valve and the EGR
valve comprise the actuating components of the
control loop. The EGR vacuum regulator valve has
a vacuum input from the manifold distribution
pipes, a vacuum output to the EGR valve and
receives a pulse width modulated (PWM) signal
from the PCM. The PWM signal switches the
vacuum control output to the EGR valve according
to input demand from the differential pressure
feedback EGR sensor or in response to override
conditions determined by the engine management
system. The EGR valve is a vacuum operated
EGR SYSTEM
J.303.1282
Exhaust Gas
Feedback Pipe
Differential Pressure
Feedback EGR sensor
EGR Vacuum
Regulator Valve
EGR valve
Orifice

V6 Engine AJ-V6/AJ28
18diaphragm valve with no electrical connections
which opens the EGR feed pipe to the induction
manifold under the EGR vacuum regulator
control.
Where the EGR system is not fitted, a blanking
plate seals the manifold in place of the EGR valve.
Control Conditions
EGR operates over most of the engine speed/load
range but is disabled by the engine management
system under certain conditions:
¥ during engine cranking
¥ until normal operating temperature is
reached
¥ when the diagnostic system registers a failure
which affects the EGR system (eg a faulty
sensor)
¥ during idling to avoid unstable or erratic
running
¥ during wide open throttle operation
¥ when traction control is operative.
While the main control loop is based on feedback
from the differential pressure feedback EGR
sensor, the EGR rate is also modified by other
engine conditions; coolant, ambient and air
charge temperatures, barometric pressure, VVT
cam position and air charge mass. Note also that
the EGR rate increases gradually after it is enabled
on each drive cycle.

V6 EngineAJ-V6/AJ28
19
Variable Valve Timing (VVT)
A VVT system is used to allow the phasing of the
inlet valve opening to be changed relative to the
fixed timing of the exhaust valves. Two positions
are used, 30û apart, with the advanced position
occurring at 30û BTDC and overlapping with the
exhaust opening. The system is similar to that
previously used on the AJ26 V8 engine but uses
different components and a different oil feed
arrangement.
The operating regime is controlled by the engine
management system in conjunction with the
variable geometry induction system so as to
optimise torque characteristics over the engine
speed/load range. The engine torque curve with
VVT operating points is shown in the section on
the Variable Intake System. The VVT system also
provides increased amounts of ÔinternalÕ EGR
under certain speed/load operating conditions.
VVT Oil Feed
The VVT/sprocket unit is fixed on the nose of the
inlet camshaft via a locating pin and hollow bolt
and is driven directly by the timing chain. Unlike
the VVT systems on the V8 engines, the oil feed
J.303.1288
VVT OIL FEED
J.303.1288
VVT Unit
VVT Oil
Control Valve
D.303.1361
VVT TIMING DIAGRAM
D.303.1361
Inlet Camshaft RetardedInlet Camshaft Advanced
Inlet opens TDC
Exhaust closes
11.5û ATDCInlet opens
30û BTDCExhaust closes
11.5û ATDC
TDC
Inlet closes
36û ABDC
Exhaust
opens 57.5û
BBDC Inlet closes
66û ABDCExhaust opens
57.5û BBDC41.5û Overlap 11.5û Overlap
Inlet Camshaft
Valve Overlap
Exhaust Camshaft

V6 Engine AJ-V6/AJ28
20to each VVT unit is supplied via fixed oilways in
the cylinder head and not through a separate
bush carrier. This arrangement requires a feed
through the camshaft side of the VVT unit from
the main cylinder head supply. The oil feed is
controlled by the VVT oil control valve, a solenoid
operated shuttle valve, which is bolted directly to
the cylinder head. From the oil control valve, the
flow is via the thrust bearing cap, through
drillings in the camshaft and then through the
hollow fixing bolt which secures the VVT unit.
Drain holes are provided at the rear (camside)
face of the VVT unit for any residual oil which has
seeped past the piston.
Operation
Operation is similar to that of the two stage V8
VVT system. With the oil control valve open, oil
pressure on the helical drive piston is increased,
rotating the cams to the advanced position.
When the valve closes, oil pressure reduces and
the return spring pushes the piston back to thefully retarded position.
The oil control valve is controlled by a 300Hz
PWM signal from the PCM which sets it to either
the fully open or fully closed position.
J.303.1306
VVT OPERATION
VVT Unit with
oil pressure
VVT oil
control valve
open
VVT oil
control valve
closed
VVT Unit with oil
pressure reduced
J.303.1306

V6 EngineAJ-V6/AJ28
21
Air Induction System
range, the manifold geometry can be set to three
different configurations, each of which maximises
the tuning effect over different parts of the range.
This variable geometry is achieved by the use of
two gate valves, the intake manifold tuning (IMT)
valves, which are controlled by the engine
management system.Air Intake
The air induction system consists of the intake
ducting and air cleaner, the throttle body, tuned
manifold assembly and lower manifold (see Fuel
System).
The air cleaner connects to the throttle body via a
lateral mounted intake pipe with resonator box. A
separate duct, housing the MAF sensor, fits
between the air cleaner and resonator pipe. The
IAT sensor is located in the intake resonator pipe.
Variable Intake System
(see illustration on page 23)
The induction manifold is specially designed to
optimise torque across the engine speed/load
range. The air charge enters the induction
manifold from the throttle body and passes
through a plenum chamber for distribution to the
cylinders via the manifold runners. The function
of the plenum chamber is to provide a resonance
(or maximising) effect such that large pulses of
charge air are produced which will arrive at the
inlet ports at the correct time for induction into
the cylinders. This ram charging action is only
effective over a restricted speed/load range for a
particular plenum chamber volume and geometry.
To extend the effect over the whole engine speed
J.303.1379
AIR INTAKE
J.303.1379
Air CleanerIntake DuctingMAF Sensor
IAT SensorThrottle Body
Tuned Manifold Assembly

V6 Engine AJ-V6/AJ28
22
D.303.1217
INDUCTION MANIFOLD
D.303.1217
Top IMT valve
Bottom
IMT valve
Construction
The induction manifold is a single piece
aluminium alloy casting which mounts to the
cylinder head induction ports via the lower
manifold assembly. The plenum chamber is split
into upper and lower compartments with two
connecting holes and each compartment is fitted
with an IMT valve.
The IMT valves are identical, solenoid operated,
with a gate or paddle which rotates through 90û
between open and closed positions. The valves
can only be set to either of these two positions.IMT Valve Operation
(see illustration on page 23)
The two IMT valves are set to one of the following
combinations:
¥ With both valves closed, there is no
communication between the upper and lower
plenum chambers and the ram charge effect
is not present
¥ With the top valve open and the bottom
valve closed, the upper and lower plenum
chambers are linked via the front connecting
hole allowing pressure waves to be
communicated and creating the ram charge
effect.
¥ With both valves open, a second link is
opened between the upper and lower

V6 EngineAJ-V6/AJ28
23
J.303.1344
VARIABLE INTAKE SYSTEM
Both IMT valves Closed
Top IMT valve Open and the
Bottom IMT valve Closed
Both IMT valves open
J.303.1344

V6 Engine AJ-V6/AJ28
24
J.303.1358
TORQUE CHARACTERISTICS
Top inlet manifold tuning valve
Advanced
Closed
325
D.303.1358
Side inlet manifold tuning valve
Open
Closed
Closed
ClosedOpen
Retarded
V. V. T.
175
200
225
250
275
300
125
150
2000700060005000400030001000
Engine Speed (rpm)
Brake Torque (Nm)
chambers via the rear connecting hole,
further increasing the ram effect.via the rear
connecting hole.
System Performance
The valve open/close combinations across the
engine speed range have been selected in
conjunction with the VVT system to provide an
optimised torque curve. Referring to the graph, it
can be seen that there are five states that the IMT
valves and VVT can adopt throughout the engine
speed range.

V6 EngineAJ-V6/AJ28
25
Throttle Control System
D.303.1219
Introduction
A fully electronically controlled throttle is fitted,
requiring no mechanical connection between the
accelerator pedal and throttle body. The driver
operates a normal foot pedal and a transducer on
the pedal shaft converts the mechanical rotation
to electrical signals which are sent to the
powertrain control module (PCM) to indicate
driver demand. Signals requesting the desired
throttle plate angle are sent from the PCM to an
electronic module on the throttle assembly, the
throttle actuator control (TAC) module, which
provides closed loop control of the motorised
throttle plate. The actual angle of the throttle
plate is indicated to the PCM by the throttle
position (TP) sensor.
The throttle assembly is mechanically simpler
than those used on previous Jaguar vehicles,
consisting essentially of a motor driven throttle
plate with no other actuators or vacuum devices
(eg cruise control).
Operation is designed to be transparent to the
driver with a total delay of less than 70ms
between pedal actuation and throttle movement.
THROTTLE BODY
Control Components
Throttle Assembly
The electronic throttle assembly consists of four
component sub-assemblies:
¥ throttle body
¥ drive motor unit
¥ throttle actuator control (TAC) module
¥ throttle position (TP) sensor
The throttle body is an aluminium casting with a
70mm air intake bore, housing a shaft with brass
throttle plate, rotating in ball bearings, and with a
spur gear and return spring fitted to the drive
end. A stop screw against the spur gear is pre-
adjusted and sealed on assembly to set the
throttle mechanical closed position and a second
stop prevents the throttle plate from being driven
beyond the full throttle position. The internal
tooth spur gear is driven directly from the motor
shaft which is offset to the throttle shaft. The
motor drive unit is an integral assembly
containing the motor, an inductive position
encoder and the mating connector to the TAC
module. Should the motor fail, the return spring
will move the throttle plate to the closed position.
The TAC module consists of a printed circuit
board enclosed within an aluminium module with
D.303.1219