Hyundai Santa Fe (TM): Exhaust Emission Control System / CVVT (Continuously Variable Valve Timing) System. Description and operation

Hyundai Santa Fe (TM) 2019-2023 Service and Repair Manual / Emission Control System / Exhaust Emission Control System / CVVT (Continuously Variable Valve Timing) System. Description and operation

Description
Continuous Variable Valve Timing (CVVT) system advances or retards the valve timing of the intake and exhaust valve in accordance with the ECM control signal which is calculated by the engine speed and load.
By controlling CVVT, the valve over-lap or under-lap occurs, which makes better fuel economy and reduces exhaust gases (NOx, HC) and improves engine performance through reduction of pumping loss, internal EGR effect, improvement of combustion stability, improvement of volumetric efficiency, and increase of expansion work.
This system consist of
–
the CVVT Oil Control Valve (OCV) which supplies the engine oil to the cam phaser or runs out the engine oil from the cam phaser in accordance with the ECM PWM (Pulse With Modulation) control signal,
–
the CVVT Oil Temperature Sensor (OTS) which measures the engine oil temperature,
–
and the Cam Phaser which varies the cam phase by using the hydraulic force of the engine oil.
The engine oil getting out of the CVVT oil control valve varies the cam phase in the direction (Intake Advance/Exhaust Retard) or opposite direction (Intake Retard/Exhaust Advance) of the engine rotation by rotating the rotor connected with the camshaft inside the cam phaser.

Operation Principle
The CVVT has the mechanism rotating the rotor vane with hydraulic force generated by the engine oil supplied to the advance or retard chamber in accordance with the CVVT oil control valve control.
  
•
The variable force solenoid (VFS) changes its force depending on the PWM duty to control the stroke of the OCV.
•
It also controls the lock, unlock, advanced, retarded, and holding functions.
[CVVT System Mode]

(1) Low Speed / Low Load
 (2) Part 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
 Completely Advance
 * Valve Under-lap
* Improvement of combustion stability
 Completely Retard
 * Valve Under-lap
* Improvement of combustion stability
(2) Part Load
 Retard
 * Increase of expansion work
* Reduction of pumping loss
* Reduction of HC
 Retard
 * Reduction of pumping loss
(3) Low Speed
/High Load
 Retard
 * Increase of expansion work
 Advance
 * Prevention of intake back flow (Improvement of volumetric efficiency)
(4) High Speed
/High Load
 Advance
 * Reduction of pumping loss
 Retard
 * Improvement of volumetric efficiency

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