CVVT (Continuously Variable Valve Timing) System Description

The Continuously Variable Valve Timing (CVVT) system advances or retards the intake and exhaust valve timing according to the ECM control signal, which is calculated from engine speed and load. Under CVVT control, valve overlap or underlap is produced, which provides better fuel economy and reduced exhaust emissions (NOx, HC). CVVT improves engine performance by reducing pumping losses, internal exhaust gas recirculation effect, improving combustion stability, improving volumetric efficiency and increasing expansion work. This system consists of

• CVVT oil control valve (OCV), which supplies engine oil to the camshaft phaser or drains engine oil from the camshaft phaser according to the ECM PWM (Pulse Width Modulation) control signal,
• CVVT oil temperature sensor (OTS), which measures engine oil temperature,
• and Cam Phaser, which changes the cam phase by hydraulic force of engine oil.

Engine oil flowing from the CVVT oil control valve changes the camshaft phase in the advance direction (Intake Advance/Exhaust Retard) or the opposite direction (Intake Retard/Exhaust Advance) relative to engine rotation, by rotating the rotor connected to the camshaft inside the camshaft phaser.