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Engine Mechanical System

CVVT and Camshaft Description and Operation

In this manual: Engine Mechanical System
General Information — 15Maintenance — 7Engine Mechanical System — 84Engine Electrical System — 49Emission Control System — 22Fuel System — 95Clutch System — 28Manual Transmission — 21Dual Clutch Transmission (DCT) System — 47Drive Shaft and Axle — 20Suspension System — 36Steering — 23Restraints — 39Brake System — 54Body (Interior and Exterior) — 209Body Electrical System — 254Heating, Ventilation, and Air Conditioning — 56
~2min read

Description

The Continuously Variable Valve Timing (CVVT) system advances or retards the valve timing of the intake and exhaust valves in accordance with the control signal from the ECM, which is calculated based on engine speed and load. Under CVVT control, valve overlap or underlap is achieved, which improves fuel economy, reduces exhaust emissions (NOx, HC), and improves engine performance by reducing pumping losses, the internal exhaust gas recirculation effect, improving combustion stability, improving volumetric efficiency, and increasing expansion work. This system consists of
  • 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,
  • CVVT Oil Temperature Sensor (OTS), which measures engine oil temperature,
  • and Cam Phaser, which changes the cam phase by hydraulic force of engine oil.
Engine oil flowing from the CVVT oil control valve changes the camshaft phase in the advance direction (intake advance/exhaust retard) or in 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

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

[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

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