Continuously Variable Valve Lift Assembly

The Continuously Variable Valve Lift (CVVL) assembly is a non-serviceable assembly for control of the intake valve lift. The CVVL assembly temperature sensor can be removed from the CVVL assembly if required. The CVVL assembly is fixed to the top of the camshaft carrier by 10 bolts.

The CVVL assembly converts the camshaft motion into the valve lift through the use of a hydraulic circuit. The valve lift can be adjusted through the use of the oil flow.

The intermediate hydraulic chambers open the valves by means of oil pressure. The oil is allowed to flow to the chambers that actuate the valves dependent on whether a solenoid is actuated or not. Opening and closing of the solenoid allows the operation of the CVVL assembly in the four different lift modes outlined below. The solenoid is controlled by the Powertrain Control Module (PCM) based on calculated engine load values.

The CVVL assembly ultimately allows the control of air in to the cylinder by delaying the valve opening, or closing the valve early.

There are four operating modes:

• Full lift mode - The valves are fully opened and closed as normal. The valves are controlled by the camshaft profile. This mode is used at high engine speeds to obtain maximum engine power.
• The late intake valve opening mode - The opening of the intake valves is delayed. The intake valves open for a shorter period at lower lift - giving benefits to the fuel economy at some speed and load sites.
• The early intake valve closing mode - The intake valves are closed hydraulically before the camshaft profile would normally allow. This reduces pumping losses, increases the engine output per liter and prevents an undesirable backflow of the fuel mixture into the intake ports.
• Composite mode - A combination of the late intake valve opening mode and the early intake valve closing mode.