Kia Rio: Exhaust Emission Control System / CVVT (Continuously Variable Valve Timing) System

Description and operation

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 which is 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, giving internal EGR effect, improving combustion stability and volumetric efficiency, and increasing expansion work.

This system consists of

The engine oil which is supplied from the CVVT oil control valve changes the cam phase in the direction (Intake Advance/Exhaust Retard) or opposite direction (Intake Retard/Exhaust Advance) of the engine rotation by rotating the rotor connected with the camshaft inside the cam phaser.

It increases the retarded amount compared to the default state to expand the operating range of the variable valve timing system.

The cam phase is fixed mechanically so that it is locked at the middle position.

The CVVT has the mechanism of rotating the rotor vane with hydraulic force generated by the engine oil supplied to the advance or retard chamber in accordance with the CVVT oil control valve control.

• The variable force solenoid (VFS) changes its force depending on the PWM duty to control the stroke of the OCV. • It also controls the lock, unlock, advanced, retarded, and holding functions.

[CVVT System Mode]