Pic. 3.54. Location of oil control valve (OCV) at the rear of the cylinder head
The system includes a power train control unit (PCM — Powertrain Control Module), oil control valve (OCV) (pic. 3.54) and the intake camshaft pulley/drive assembly.
Power train control unit (PCM) controls the operation of the oil control valve (OCV) based on information from the following sensors:
- vehicle speed sensor (VSS);
- throttle position sensor (TPS);
- air flow meter sensor (MAP);
- coolant temperature sensor (ECT).
Oil control valve (OCV), driven by the control unit (PCM), increases or decreases the oil pressure supplied to the intake camshaft pulley/actuator.
The intake camshaft sprocket is equipped with an inner sleeve that is attached to the camshaft. The inner sleeve consists of a series of fixed vanes in such a way that pressure is used as a wedge to turn them and thus turn the camshaft. As oil pressure increases, the angle of rotation of the camshaft increases.
When supplying oil to the vanes from the advanced side, the drive can turn the camshaft up to 21°clockwise. When oil is supplied from the retard side, the actuator will rotate the shaft counterclockwise to the 0°advance position, which is the normal position when the engine is running at idle speed. The PCM can also send a signal to the oil control valve to stop the flow of oil and hold the camshaft in its current position.
When the engine is running at light loads, the VVT system will reduce the camshaft advance angle, resulting in a decrease in the period of valve overlap and stabilization of engine power.
When the engine is running at moderate loads, the VVT system will increase the camshaft advance angle to increase the valve overlap period, resulting in increased engine power and reduced emissions of harmful substances in the exhaust gases.
When the engine is under heavy load at low engine speeds, the VVT system will increase the camshaft advance angle to close the intake valves faster, resulting in increased engine power at low and medium speeds.
When the engine is under heavy load at high engine speeds, the VVT system will decrease the camshaft advance to delay the closing of the intake valves, resulting in increased engine power.