VariableValveTiming system (VVT) adjusts the phase of the engine cam through the equipped control and execution system, so that the valve opening and closing time changes with the change of the engine speed, thus improving the charging efficiency and increasing the engine power.
VVT technology has a history of more than 30 years. Its principle is to adjust the intake (exhaust) amount, valve opening and closing time and angle according to the engine operation, so that the intake amount can reach the optimal value and the combustion efficiency can be improved. Its advantages are fuel saving and high power ratio; The disadvantage is the lack of speed and torque in the middle section.
Extended data:
Working principle:
Piston engines usually intake and exhaust air by lifting the throttle valve, which is directly or indirectly driven by the cam on the camshaft. In each intake and exhaust cycle, the cam drives the valve to open (lift) for a certain time (overlap time).
At high speed, the engine needs more air, but the intake valve may close before the required air completely enters, which will reduce the performance, so the opening and closing timing of the valve is very important. The continuously opened valve will cause the fuel to be discharged from the engine without burning, which will reduce the performance of the engine and increase the exhaust pollution, so the idle speed of the engine for competition should not be too low.
The crankshaft drives the camshaft through a timing belt, gear or chain. The profile and position of the cam on the camshaft are usually optimized for a specific engine speed, which usually reduces the torque of the engine at low speed and the power at high speed. VVT technology can make it change according to the working conditions of the engine and improve the efficiency and power of the engine.
Baidu encyclopedia -VVT
Baidu encyclopedia -vvt engine