Kia Picanto JA Quiz
Emission Control System

Continuously Variable Valve Timing (CVVT) System

In this manual: Emission Control System
General Information — 8Maintenance — 30Engine Mechanical System — 46Engine Electrical System — 14Emission Control System — 11Engine Control System/Fuel System — 46Clutch System — 12Manual Transmission — 10Drive Shaft and Axle — 8Suspension System — 15Steering — 9Restraints — 17Brake System — 22Body (Interior and Exterior) — 104Body Electrical System — 80Heating, Ventilation, and Air Conditioning — 17
~2min read

Description and Operation

Description

The Continuously Variable Valve Timing (CVVT) system advances or retards the timing of the intake and exhaust valves according to the control signal from the ECM, which is calculated based on engine speed and load. By controlling the CVVT, valve overlap or underlap is adjusted, providing better fuel economy and reduced exhaust emissions (NOx, HC). The CVVT improves engine performance by reducing pumping losses and internal exhaust gas recirculation effect, improving combustion stability and volumetric efficiency, and increasing expansion work. This system consists of:
  • The CVVT oil control valve (OCV) supplies engine oil to the cam phaser or drains engine oil from the cam 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 from the CVVT oil control valve changes the position of the cam phaser in the advance direction (intake advance/exhaust retard) or in the retard direction, opposite to engine rotation (intake retard/exhaust advance), by rotating the rotor connected to the camshaft inside the cam phaser.

Operating Principle

The CVVT has a rotor vane mechanism that rotates by hydraulic force. It is generated by engine oil supplied to the advance or retard chamber according to the control of 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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