CVVT (Continuously Variable Valve Timing) System: Description

Fig 1: CVVT (Continuously Variable Valve Timing) System Diagram

Courtesy of HYUNDAI MOTOR CO.

The CVVT (Continuously Variable Valve Timing) is installed on the intake/exhaust camshaft which monitors intake/exhaust valve open and close timing in order to improve engine performance.

The intake/ exhaust valve timing is optimized by CVVT system depending on engine rpm.

This CVVT system improves fuel efficiency and reduces NOx emissions at all levels of engine speed, vehicle speed, and engine load through the effects of the EGR by valve overlap optimization.

The CVVT changes the phase of the intake camshaft via oil pressure. It changes the intake valve timing continuously.

[2.4 DOHC]

Fig 2: CCVT Graph - 2.4 DOHC

Courtesy of HYUNDAI MOTOR CO.

DRIVING CONDITION CHART

Driving condition	Exhaust valve		Intake valve
Driving condition	Valve timing	Effect	Valve timing	Effect
Low speed/ Low load (1)	Maximum advance	Valve under-lap, Stable combustion	Maximum advance	Valve under-lap, Stable combustion
Part load (2)	Retard	Pumping loss reduction, Enhanced power, HC reduction	Retard	Pumping loss reduction
Low speed/ High load (3)	Retard	Enhanced power	Advance	Prevention of intake flowing backward
High speed/ High load (4)	Advance	Pumping loss reduction	Retard	Improvement of volume efficiency

[3.3V6]

Fig 3: CCVT Graph - 3.3 V6

Courtesy of HYUNDAI MOTOR CO.

Fig 4: CCVT Overlap Graph

Courtesy of HYUNDAI MOTOR CO.