Kia Stonic Quiz
Emission control system

CVVT (Continuously Variable Valve Timing) System

In this manual: Emission control system
General Information — 8Maintenance — 31Engine Mechanical — 49Engine Electrical — 15Emission control system — 11Engine Control System/Fuel System — 45Clutch System — 12Manual Transaxle System — 11DCT (Dual Clutch Transmission) System — 16Drive Shafts and Axles — 9Suspension — 16Steering — 10restraint system — 15Braking system — 22Body (Interior and Exterior) — 89Rear Seat — 16Electrical System — 25Electrochromic Interior Rear View Mirror — 64Heating, Ventilation, and Air Conditioning — 31
~2min read

Description and Operation

Description

The Continuously Variable Valve Timing (CVVT) system adjusts the valve timing of the intake and exhaust valves to advance or retard in accordance with the control signal from the ECM, which is calculated based on engine speed and load.

The CVVT system controls valve overlap, thereby improving fuel economy and reducing exhaust emissions (NOx, HC). The CVVT system improves engine output by reducing pumping losses, increasing internal EGR effect, improving combustion stability, improving volumetric efficiency and increasing expansion work.

This system consists of:

  • CVVT oil control valve (OCV), which supplies engine oil pressure to the cam phaser or regulates it by PWM (Pulse Width Modulation) in accordance with the control signal from the ECM, allowing the cam phaser to operate,

  • CVVT oil temperature sensor (OTS), which measures the engine oil temperature,

  • and cam phaser, which adjusts the camshaft phase in accordance with the oil pressure supplied. Hydraulic force varies.

Engine oil flowing through the CVVT oil control valve moves the camshaft in the advance direction (intake advance / exhaust retard) or in the reverse direction (intake retard / exhaust advance) relative to engine rotation by rotating the rotor connected to the camshaft in the cam phaser.

OPERATING PRINCIPLE

The CVVT uses a hydraulic mechanism in which the vane rotates by the pressure of engine oil. The oil supply to the chambers that advances or retards the phase is 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
Control		 Effect Valve
Control		 Effect
(1) Low Speed
/Low Load		 Full
EARLY		 * Reduced valve overlap
* Improved combustion efficiency		 Full
LATE		 * Reduced valve overlap
* Improved combustion efficiency
(2) Partial load LATE * Greater expansion
* Minimized pumping losses
* Reduced HC emissions		 LATE * Minimized pumping losses
(3) Low Speed
/High Load		 LATE * Greater expansion EARLY * Prevention of intake air backflow (improved efficiency)
(4) High Speed
/High Load		 EARLY * Minimized pumping losses LATE * Improved efficiency

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