Kia Rio: Cylinder Head Assembly / CVVT & Camshaft

Kia Rio 2017-2024 YB Service Manual / Engine Mechanical System / 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
Driving Condition	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

Repair procedures

Removal

1.	Remove the timing chain. (Refer to Timing System - "Timing Chain")

Remove the intake CVVT (A) and exhaust CVVT (B).

•	To prevent impurities from entering intake OCV & center bolt, wear rubber gloves.

•	When removing the intake OVC & center bolt and exhaust CVVT bolt, place a wrench at position (A) to prevent the camshaft from rotating.

[Intake camshaft]

[Exhaust camshaft]

3.	Remove the front camshaft bearing cap (A) and camshaft bearing cap (B).

4.	Remove the intake camshaft (A) and exhaust camshaft (B).

Inspection

Camshaft

Inspect cam lobes.

Using a micrometer, measure the cam lobe height.

Cam height

Intake : 36.4183mm (1.4337in)

Exhaust : 36.1543mm (1.4233in)

If the cam lobe height is less than standard, replace the camshaft.

2.	Check the surface of the camshaft journal for wear. If the journal is worn excessively, replace the camshaft.

Inspect the camshaft journal clearance.

(1)	Clean the bearing caps and camshaft journals.

(2)	Place the camshafts on the cylinder head.

(3)	Lay a strip of plastigage across each of the camshaft journals.

(4)

Install the front camshaft bearing cap (A) and the camshaft bearing cap (B) as following method with specified torque.

Tightening torque

Front camshaft bearing cap : 9.8 N·m (1.0 kgf·m, 7.2 lb·ft)

Camshaft bearing cap : 5.9 N·m (0.6 kgf·m, 4.3 lb·ft)

Front camshaft bearing cap : 18.6 - 22.6 N·m (1.9 - 2.3 kgf·m, 13.7 - 16.6 lb·ft)

Camshaft bearing cap : 11.8 - 13.7 N·m (1.2 - 1.4 kgf·m, 8.7 - 10.1 lb·ft)

Do not turn the camshaft.

(5)	Remove the bearing caps.

(6)

Measure the plastigage at its widest point.

Camshaft bearing oil clearance

Intake : 0.027 - 0.057mm (0.0010 - 0.0022in)

Exhaust : 0.027 - 0.057mm (0.0010 - 0.0022in)

If the oil clearance is greater than maximum, replace the camshaft. If necessary, replace cylinder head.

(7)	Completely remove the plastigage.

(8)	Remove the camshafts.

Inspect the camshaft end play.

(1)	Install the camshaft bearing cap.

(2)

Using a dial indicator, measure the end play while moving the camshaft back and forth.

If the end play is greater than specification, replace the camshaft.

If necessary, replace the bearing caps and cylinder head as a set

Camshaft end play

Intake : 0.1 - 0.2 mm (0.0039 - 0.0078 in)

Exhaust : 0.1 - 0.2 mm (0.0039 - 0.0078 in)

(3)	Remove the camshafts.

Exhaust CVVT Assembly

Inspect CVVT assembly.

(1)	Clamp the exhaust camshaft using a vise. Be careful not to damage the cam lobes and journals in the vise.

(2)	Check that the exhaust CVVT is locked by turning it clockwise or counterclockwise. It must not rotate.

(3)	Exhaust CVVT : Seal one of the two retard holes in the camshaft journal with tape.

(4)

Exhaust CVVT : Apply approx. 150 kPa (1.5 kgf/cm², 21 psi) of compressed air into the unsealed retard hole to release the lock.

Cover the oil paths with a piece of cloth when applying compressed air to prevent oil from spraying.

(5)

Exhaust CVVT : With compressed air applied, rotate the CVVT into the retard direction (clockwise) and check that the CVVT turns smoothly.

CVVT phasing range

Exhaust : 20° ± 1° (from the most advanced position to the most retarded position)

(6)	Exhaust CVVT : Rotate the CVVT into the most advanced position (counterclockwise) and then check that the CVVT is locked.

Installation

1.	Install the intake camshaft (A) and exhaust camshaft (B).

Install the front camshaft bearing cap (A) and the camshaft bearing cap (B) as following method with specified torque.

Tightening torque

A : 18.6 - 22.6 N·m (1.9 - 2.3 kgf·m, 13.7 - 16.6 lb·ft)

B : 11.8 - 13.7 N·m (1.2 - 1.4 kgf·m, 8.7 - 10.1 lb·ft)

Do not turn camshaft

Install the intake CVVT (A) and exhaust CVVT (B).

Tightening torque

Intake :

85.3 - 95.1 N·m (8.7 - 9.7 kgf·m, 62.9 - 70.2 lb·ft)

Exhaust :

63.7 - 73.5 N·m (6.5 - 7.5 kgf·m, 47.0 - 54.2 lb·ft)

•	Do not use any dropped intake OCV & center bolt.

•	When installing intake CVVT, apply engine oil on cross section (A) of OCV.

4.	Install in the reverse order of removal.

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