Kia Niro: Cylinder Head Assembly / CVVT & Camshaft 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, 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 increased expansion work.

This system consists 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 released from 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 of 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.

1.

Intake CVVT

2.

Exhaust CVVT

[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
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

Cylinder Head Cover Repair procedures
Removal Engine removal is not required for this procedure.    • Use fender covers to avoid da ...

CVVT & Camshaft Repair procedures
Removal    • Use fender covers to avoid damaging painted surfaces. ...

Other information:

Kia Niro 2017 (DE HEV) Service Manual: General safety information and caution
Safety Precaution Precautions to take before servicing high voltage system    Hybrid vehicles have high voltage batteries. Incorrect handling of high voltage sy ...

Kia Niro (DE HEV) Owners Manual: On inclines
During uphill or downhill driving, the smart cruise control system may not detect a moving vehicle in your lane, and cause your vehicle to accelerate to the set speed. Also, the vehicle speed will rapidly down when the vehicle ahead is recognized suddenly. Select the appropriate set ...

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