variable valve timing and lift (part two)

This type of VVt can change both valve timing and valve lift. It gives the engine a smoother engine speed and better high speed performance.
The multi valve DOHC engine uses shaft mounted rocker arms to transmit cam lobe movement to the valve stem.
The camshaft has three lobes for each pair of intake valves and exhaust valves. The third rocker arm is the mid rocker arm. It is betweem each pair of valves. each rocker arm has a built in hydraulic piston. Operation of the piston engages or disengages the rocker arm. The difference in performance occurs because each cam lobe is different. The centre cam lobe is for high Rpm. The primary and secondary cam lobes is for lower Rpm.
Sensors on the engine sends information on engine speed, engine load, vehicle speed and coolant temperature to the ECU. At pre-determined switchover point, the ECU sends a signal to solenoid. As the solenoid opens and closes, the engine oil pressure is sent to the piston in the selected rocker arms. the rocker arm then engages or disengages . This changes the cam lobe operating the valves. The change from the low lift of the outboard lobes to the higher lift and longer duration of the centre lobes take about 0.1 second. The system does not engage at low speed or when the engine is under no load.