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The valve timing mechanism of engine is in charge of providing fresh air required by gasoline combustion to air cylinder and discharge exhaust gas.

For common engines, the switching time of intake and exhaust valves is fixed and decided by camshaft curve; it cannot automatically adjust based on different engine speed and working conditions and cannot reach ideal intake and exhaust efficiency.

VVT can make engine reach satisfactory valve lift both under high or low speed of revolution, and improve high speed power and low speed torque of engine.