Continuous Variable Valve Timing (CVVT) system advances or retards the valve timing of the intake and exhaust valve in accordance with the ECM control signal calculated by the engine speed and load.

By controlling CVVT, the valve overlap or underlap occurs, which makes better fuel economy, reduces exhaust gases (NOx, HC) and improves engine performance by reducing pumping loss and internal EGR effect, improving combustion stability and volumetric efficiency, and increasing expansion work.

This system cousists of

- the CVVT Oil Control Valve (OCV) which supplies the engine oil to the cam phaser or cuts the engine oil from the cam phaser in accordance with the PWM (Pulse With Modulation) control signal of ECM.

- the Cam Phaser which varies the cam phase by using the hydraulic force of the engine oil.

The engine oil transferred from the CVVT oil control valve changes the cam phase in the forward (Intake Aduance / Exhaust Retard) or the reverse (Intake Retard / Exhaust Advance) direction of the engine rotation by rotating the rotor connected to the camshaft inside the cam phaser.