2010 JAGUAR XFR Timing

1 VCT units 2 Intake camshaft VCT solenoid 3 Camshaft position sensors 4 Exhaust camshaft VCT solenoid The VCT system varies the timing of the intake and exhaust camshafts to deliver optimum engine power, efficiency and emissions. The timing of the intake camshafts has a range of 62 degrees of crankshaft angle. The timing of the exhaust
camshafts has a range of 50 degrees of crankshaft angle.
In the base timing position:

The intake camshafts are fully retarded.
The exhaust camshafts are fully advanced.

VCT Operating Ranges
Camshaft Valve Opens Valve Closes Intake 29 degrees BTDC (before top dead center) to 33 degrees ATDC (after top dead center) 207 to 269 degrees ATDC Exhaust 244 to 194 degrees BTDC 6 to 56 degrees ATDC The system consists of a VCT unit and a VCT solenoid for each camshaft. The ECM controls the system using PWM (pulse width modulation) signals to the VCT solenoids.
The torsional energy generated by the valve springs and the inertia of the valve train components are used to operate the
system. Variable Camshaft Timing

1 Bolt (3 off) 2 VCT unit 3 Filter 4 Camshaft 5 Inner plate 6 Housing and sprocket 7 Rotor assembly 8 Reed plate 9 Spring and lock pin 10 Spring (3 off) 11 Tip seal (3 off) 12 Spring (2 off) 13 Tip seal (2 off) 14 Spring The VCT units change the position of the camshafts in relation to the timing chains.

16 Bias spring 17 Snap ring 18 Reluctor ring 19 Center plate 20 Snap ring 21 Screw (6 off) 22 Spool valve 23 Outer plate Each VCT unit is attached to the camshaft by three bolts. A rotor assembly and a reed plate are installed inside a sprocket housing, which consists of a sprocket, an outer plate and an inner plate held together by six screws.

A reluctor ring, for the CMP (camshaft position) sensor, a center plate and a bias spring are installed at the front of the VCT unit. The ends of the bias spring locate on the center plate assembly and the sprocket housing, to give a turning moment to
the camshaft in the advance direction. A snap ring locates the reluctor ring on to a sleeve installed in the center of the rotor
assembly. The opposite end of the sleeve locates in a bore in the front face of the camshaft, which contains a filter.

A spring and spool valve are installed in the rotor assembly sleeve and retained by a snap ring. The spring keeps the spool
valve in contact with the armature of the related VCT solenoid.
Each VCT unit is supplied with engine oil from an oil gallery in the cylinder head, through the camshaft front bearing cap and a bore in the center of the camshaft.
Variable Camshaft Timing Solenoids
The VCT solenoids control the position of the spool valves in the VCT units.


The VCT solenoids are installed in the front upper timing covers, immediately in front of their related VCT units. Each VCT solenoid is secured with two screws and sealed with an O-ring. A two pin electrical connector provides the interface with the
engine harness.

Each VCT solenoid incorporates a spindle that acts on the spool valve in the related VCT unit to advance and retard the camshaft timing. The VCT solenoids operate independently and are controlled by a PWM signal from the ECM. www.JagDocs.com

Variable Camshaft Timing Operation

When the engine is running, the compression and expansion of the valve springs causes momentary increases and decreases
in the torque acting on the camshafts. These momentary changes of torque are sensed in the VCT units and used to change the camshaft timing.


ItC
em Description A Camshaft torque B Camshaft rotation (degrees) Valve opening D Peak lift E Valve closing 1 1000 rev/min 2 4000 rev/min 3 7000 rev/min 4 Inertia effects from valve train rotating components 5 Force caused by valve spring 6 Bias torque from friction
NOTE: Intake camshaft VCT unit shown. For exhaust camshaft VCT unit, read advance for retard and retard for advance.

Variable Camshaft Timing Unit Schematic - Advance


To advance the camshaft timing, the ECM adjusts the signal to the VCT solenoid to move the spool valve so that the advance chamber oil passage is closed and the retard chamber oil passage is connected to inlet oil.

Each momentary increase of the torque acting on the camshaft generates a pressure pulse in the retard chamber. Oil moves
from the retard chamber, through the spool valve and the advance check valve to the advance chamber, to equalize the
pressures in the two chambers. The displacement of oil from the retard chamber causes the rotor assembly to advance in
relation to the sprocket housing. Each momentary decrease of torque acting on the camshaft also generates a pressure pulse
in the advance chamber, but, with the advance chamber oil passage closed, no movement of oil between the advance and
retard chambers occurs and the rotor assembly cannot move in the retard direction.

valve in the null position. In the null position, the advance and retard chamber oil passages are both closed by the spool valve
and the rotor assembly is hydraulically locked to the sprocket housing. Variable Camshaft Timing Unit Schematic - Null

chamber oil passage and connect the advance chamber oil passage to the inlet oil.

Each momentary decrease of the torque acting on the camshaft causes oil to transfer from the advance chamber, through the
spool valve and the retard check valve to the retard chamber, and so retard the camshaft timing. www.JagDocs.com

1 Oil pump outlet tube 2 Anti-drain valve 3 Oil cooler 4 Oil filter 5 Piston cooling jets 6 Timing chain lubrication jets 7 Oil evacuation tube 8 Oil pump 9 Oil temperature and level sensor 10 Oil pick-up The oil pump is attached to the underside of the windage tray. The input shaft of the oil pump is driven from the front of the
crankshaft, by the auxiliary chain, at 0.87 engine speed.

The oil pump draws oil from the sump pan through a centrally mounted pick-up pipe. The oil is pressurized and pumped
through an output tube to the cylinder block. After passing through an anti-drain valve and a plate type oil cooler, the oil is
filtered by a replaceable cartridge installed on the front of the RH cylinder head. LUBRICATION SYSTEM