Kia Picanto: Cylinder Head Assembly / CVVT & Camshaft

Kia Picanto JA 2017-2024 Service & Repair 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 overlap or underlap 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 and volumetric efficiency, and increase of 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 forward 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 by hydraulic force generated by the engine oil supplied to the advance or retard chamber in accordance with the CVVT oil control valve control.

[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
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 cylinder head cover. (Refer to Cylinder Head Assembly - “Cylinder Head Cover”)

2.	Remove the vacuum pump. (Refer to Cylinder Head Assembly - "Vacuum Pump")

3.	Remove the timing chain. (Refer to Timing System - “Timing Chain”)

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

When removing the CVVT assembly hold the camshaft with a wrench to prevent the camshaft from rotating.

5.	Remove the camshaft front bearing cap (A), camshaft middle bearing cap (B), and camshaft rear bearing cap (C) in the sequence shown.

6.	Remove the camshafts (A).

Inspection

Camshaft

Inspect cam lobes.

Using a micrometer, measure the cam lobe height.

Cam height

Intake : 41.79824 mm (1.6456 in)

Exhaust : 41.57000 mm (1.6366 in)

If the cam lobe height is less than standard, 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 camshaft front bearing cap (A), camshaft middle bearing cap (B), and camshaft rear bearing cap (C) in following method by tightening to the specified torque.

Tightening torque :

Step 1

A : 9.8 N·m (1.0 kgf·m, 7.2 lb·ft)

B : 5.9 N·m (0.6 kgf·m, 4.3 lb·ft)

Step 2

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)

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

Do not turn the camshaft.

When cam caps are installed, the arrows on top of caps must point outward from the engine.

(5)	Remove the bearing caps.

(6)

Measure the plastigage at its widest point.

Camshaft bearing oil clearance

Intake :

0.027 - 0.057 mm (0.0010 - 0.0022 in)

Exhaust :

0.027 - 0.057 mm (0.0010 - 0.0022 in)

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

(7)	Completely remove the plastigage.

(8)	Remove the camshaft.

Inspect the camshaft end play.

(1)	Install the camshaft (A).

(2)

Install the camshaft front bearing cap (A), camshaft middle bearing cap (B), and camshaft rear bearing cap (C) in following method by tightening to the specified torque.

Tightening torque :

Step 1

A : 9.8 N·m (1.0 kgf·m, 7.2 lb·ft)

B : 5.9 N·m (0.6 kgf·m, 4.3 lb·ft)

Step 2

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)

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

Do not turn the camshaft.

When cam caps are installed, arrows on the top of caps must point to out side of engine.

(3)

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

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)

If the end play is greater than maximum, replace the camshaft. If necessary, replace cylinder head.

(4)	Remove the camshafts.

CVVT (Continuous Variable Valve Timing) Assembly

Inspect the CVVT assembly.

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

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

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

(4)

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

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)

Intake CVVT : With compressed air applied, rotate the CVVT into the advance direction (counterclockwise) within its phasing range and check that the CVVT turns smoothly.

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

CVVT phasing range

Intake :

25° (from the most retarded position to the most advanced position)

Exhaust :

20° (from the most advanced position to the most retarded position)

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

Installation

1.	Install the camshafts (A).

Install the camshaft front bearing cap (A), camshaft middle bearing cap (B), and camshaft rear bearing cap (C) in the sequence shown.

Tightening torque :

Step 1

A : 9.8 N·m (1.0 kgf·m, 7.2 lb·ft)

B : 5.9 N·m (0.6 kgf·m, 4.3 lb·ft)

Step 2

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)

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

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

Tightening torque :

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

When installing the CVVT assembly hold the camshaft with a wrench to prevent the camshaft from rotating.

4.	Install the remaining parts in the reverse order of removal.

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