Kia Stinger CK Quiz
Emission Control System

Continuously Variable Valve Timing (CVVT) System

In this manual: Emission Control System
General Information — 8Maintenance — 27Engine Mechanical System — 47Engine Electrical System — 19Emission Control System — 12Engine Control System/Fuel System — 51Automatic Transmission System — 34All-Wheel Drive (AWD) System — 7Drive Shaft and Axle — 15Suspension System — 25Steering — 8Restraints — 19Brake System — 22Body (Interior and Exterior) — 47Front Seat Belt — 63Body Electrical System — 99Windshield Wiper/Washer — 11Heating, Ventilation, and Air Conditioning — 32
~2min read

Description and Operation

Description

The Continuously 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. By controlling CVVT, valve overlap or underlap is achieved, which improves fuel economy, reduces exhaust emissions (NOx, HC), and improves engine performance by reducing pumping losses, improving internal EGR effect, improving combustion stability, improving volumetric efficiency, and increasing expansion work.

[Intake]

The E-CVVT system is an electric continuously variable valve timing system. It is located on the intake camshaft and uses engine rotation to control the camshaft angle relative to crankshaft rotation, independent of engine oil pressure. E-CVVT controls the DC motor current (duty signal) to control the system more precisely compared to the previous hydraulic type, increasing camshaft response speed, improving starting performance, and reducing exhaust emissions. The operating range of the intake valve (valve opening angle) is also expanded, so power and fuel economy are improved.

[Exhaust]

This system consists of the CVVT oil control valve (OCV), which 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, and the cam phaser, which changes the camshaft phase using the hydraulic force of the 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 cam phaser.

Operating Principle

[Intake]

[Exhaust]

CVVT has a rotor vane mechanism that is rotated by hydraulic force from 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 / light load Fully
Advance		 * Lower valve overlap Fully
Retard		 * Lower valve overlap
* Improved combustion stability * Improved combustion stability
(2) Partial Load Retard * Increased expansion work Retard * Reduced pumping losses
* Reduced pumping losses
* Reduced HC
(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

A quick Kia Stinger CK quiz: every answer comes with an explanation and a link to the manual page.