VTEC full name is variable valve timing and lift electronic control system It can change with the engine speed, load, water temperature and other operating parameters, and adjust the timing and valve lift properly, so that the engine at high and low speed can achieve the highest efficiency. In the VTEC system, its intake camshaft has three cam faces, respectively, the top of the axis to shake the three rocker arm, when the engine at low speed or low load, three rocker arm without any connection between the left and right of the rocker arm respectively top two air intake door, so that the two have different timing and lift, to form the effect of air squeeze. At this time the middle of the high-speed rocker arm does not top the valve, just on the rocker shaft to do invalid motion. When the speed of the continuous improvement, the engine of the sensors will be monitored load, speed, speed and temperature parameters sent to the computer, computer analysis and processing of these information. When the need to change to high-speed mode, the computer issued a signal to open the VTEC solenoid valve, so that the pressure oil into the rocker shaft of the top piston, so that three rocker arm connected into one, so that two valves are operating at high speed mode.
When the engine speed is reduced to the valve is needed to change again, the computer again issued a signal, open the VTEC solenoid valve pressure opening, so that the pressure oil vent, the valve back to the low-speed operation mode.