All-New Jaguar XJ

CAMSHAFT TIMING

The AJ-V8 Gen III engines have an advanced new variable camshaft timing (VCT) system that offers increased engine response and performance. The four VCT units are activated by the positive and negative torques generated by opening and closing the intake and exhaust valves, instead of by oil pressure. This has allowed the engine oil pump to be reduced in size, saving energy and improving fuel consumption.

The naturally aspirated engine is also equipped with camshaft profile switching (CPS) on the inlet camshaft. Depending on the engine’s running conditions and the demands of the driver, the CPS will switch between a profile that is ideal for low-speed driving and another which gives increased valve lift for high performance.

Hydraulically-actuated two-piece tappets switch between profiles on the tri-lobe camshaft altering both the lift and duration (see animation right). The cam lobe profile selected for lower engine speeds has a duration of 214° and lifts the valves 5.5mm.

This optimises gas velocity for improved low-speed torque and reduces valvetrain friction for improved fuel economy.

For high-speed driving, CPS switches to a cam lobe with a duration of 250° and valve-lift of 10.5mm, allowing greater air flow for high power (click 'NEXT' on animation to illustrate). Switching is activated at 2800rpm at high load, ranging to 4500rpm at light load conditions.

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