Kia Cadenza VG Owner's Manual Quiz
Engine Mechanical System

CVVT and Camshaft Description and Operation

In this manual: Engine Mechanical System
General Information — 15Engine Mechanical System — 95Engine Electrical System — 54Emission Control System — 24Engine Control System/Fuel System — 115Automatic Transmission — 91Drive Shaft and Axle — 13Suspension System — 35Steering — 19Restraints — 46Brake System — 43Body (Interior and Exterior) — 51Body Electrical System — 245Heating, Ventilation, and Air Conditioning — 56
~2min read

Description

The Continuous Variable Valve Timing (CVVT) system advances or retards the intake and exhaust valve timing according to the control signal from the ECM, which is calculated based on engine speed and load. Under CVVT control, valve overlap or underlap is adjusted, which improves fuel economy and reduces exhaust emissions (NOx, HC). CVVT improves engine performance by reducing pumping losses, providing an internal exhaust gas recirculation effect, improving combustion stability, increasing volumetric efficiency, and increasing expansion work. This system consists of
  • CVVT oil control valve (OCV), which supplies engine oil to the phaser or drains engine oil from the phaser according to the ECM PWM (Pulse Width Modulation) control signal,
  • CVVT oil temperature sensor (OTS), which measures the engine oil temperature.
  • and Cam Phaser, which changes the camshaft phase using hydraulic pressure from the engine oil.
Engine oil flowing through the CVVT oil control valve changes the camshaft phase in the advance direction (intake advance / exhaust retard) or the retard direction (intake retard / exhaust advance) by rotating the rotor connected to the camshaft inside the cam phaser.

Operating Principle

The CVVT has a mechanism that rotates the rotor vane with hydraulic force generated by engine oil supplied to the advance or retard chamber, controlled by the CVVT oil control valve.

[CVVT System Mode]

(1) Low Speed/Low Load (2) Partial Load


(3) Low Speed/High Load (4) High Speed/High Load



Driving
Condition		 Exhaust Valve Intake Valve
Valve
Timing		 Effect Valve
Timing		 Effect
(1) Low Speed
/Low Load		 Fully
Advance		 * Lower valve overlap
* Improved combustion stability		 Fully
Retard		 * Lower valve overlap
* Improved combustion stability
(2) Partial Load Retard * Increased expansion work
* Reduced pumping losses
* Reduced HC		 Retard * Reduced pumping losses
(3) Low Speed
/High Load		 Retard * Increased expansion work Advance * Prevents intake backflow (improves volumetric efficiency)
(4) High Speed
/High Load		 Advance * Reduced pumping losses Retard * Improved volumetric efficiency

Test yourself

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