Kia Forte: Cylinder Head Assembly / CVVT & Camshaft

Kia Forte 2019-2024 (BD) Service Manual / Engine Mechanical System / Cylinder Head Assembly / CVVT & Camshaft

Components and components location

Components

1. Exhaust camshaft
2. Intake camshaft
3. Exhaust CVVT
4. Intake CVVT

5. Camshaft bearing cap
6. Camshaft front bearing cap
7. O-ring
8. Oil control valve (OCV) adapter

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.

[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")

Turn the crankshaft damper pulley so that No. 1 piston is at top dead center.

(1)	Turn the crankshaft damper pulley and align its groove with the timing mark on the timing chain cover (0° mark on the timing scale).

(2)

Check that the TDC timing marks on the intake and exhaust CVVT sprockets are in a straight line on the cylinder head surface as shown in the picture. If not, turn the crankshaft damper pulley by one revolution (360°).

Do not turn the crankshaft damper pulley counterclockwise.

(3)	Mark the timing chain links corresponding to the timing marks on the CVVT sprockets with a white marker.

3.	Remove the exhaust oil control valve (OCV) adaptor (A).

4.	Remove the camshaft bearing caps (A) in the order of image below.

Remove the engine mounting support bracket.

(1)

Put a jack under the oil pan.

Place a wooden block between the jack and the oil pan to prevent damage to the oil pan.

(2)	Disconnect the enigne ground cable (A).

(3)	Remove the engine mounting support bracket (A).

(4)	Lift the engine slightly using the jack to obtain space for releasing the timing chain tensioner.

6.	Remove the bolt (A) from the service hole in the timing chain cover.

Lock the timing chain tensioner in the fully retracted position.

(1)	Insert a pick into the service hole in the timing chain cover and lower the hole in the left side of the ratchet plate (A) on the tensioner to allow the pawl (B : located inside the tensioner behind the ratchet plate) to be lifted.

(2)	With the pawl lifted, have a helper pull up the exhaust CVVT & camshaft (A) to allow the tensioner plunger (B) to retract.

(3)

With the tensioner plunger in the fully retracted position, raise the hole in the left side of the ratchet plate (A) again through the service hole in the chain cover to align the ratchet plate hole with the hole in the tensioner body behind the ratchet plate, then lock the tensioner by inserting the pick through the ratchet plate and tensioner body holes.

8.	Separate the exhaust camshaft (A) from the exhaust CVVT by removing the bolt.

9.	Remove the exhaust CVVT (A) from the timing chain.

10.

Remove the intake CVVT & camshaft (A).

Fasten the timing chain to the engine hanger with a cable tie or strap not to allow the timing chain to fall down when removing the intake CVVT & camshaft.

11.

Remove the intake CVVT (A) from the intake camshaft (B).

When removing the CVVT bolt, hold the hexagonal portion (B) on the camshaft with a wrench to prevent the camshaft from rotating.

Inspection

Camshaft

Measure the height of the cam lobe using a micrometer and check the surface of the cam lob for wear and tear. If necessary, replace the camshaft.

Cam height

Intake : 44.15 mm (1.738 in.)

Exhaust : 43.55 mm (1.715 in.)

2.	Check the surface of the camshaft journal for wear and tear. If the camshaft journal is excessively damaged, replace the camshaft.

Inspect the camshaft journal clearance.

(1)	Clean the camshaft journals and bearing caps.

(2)	Place the camshafts in the cylinder head.

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

(4)

Install the bearing caps and tighten the bolts to the specified torque.

Tightening torque

M6 bolts :

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

M8 bolts :

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

Do not turn the camshaft.

(5)	Remove the bearing caps.

(6)

Measure the plastigauge at the widest point. If the clearance is greater than the specification, replace the camshaft. If necessary, replace the bearing caps and the cylinder head as a set.

Camshaft bearing cap oil clearance

Standard :

0.027 - 0.058 mm (0.0011 - 0.0023 in.)

Limit : 0.1 mm (0.0039 in.)

Inspect the camshaft end play.

(1)	Inspect the camshaft end play.

(2)

Measure the end play while moving the camshaft back and forth using a dial gauge. If the end play is greater than the specification, replace the camshaft. If necessary, replace the bearing caps and the cylinder head as a set.

Camshaft end play

Standard : 0.1 - 0.2 mm (0.0039 - 0.0079 in.)

(3)	Remove the camshafts.

CVVT (Continuously Variable Valve Timing) Assembly

Inspect the CVVT for smooth rotation.

(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.

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

Exhaust : 20° ± 1° (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

Install the intake CVVT (A) to the intake camshaft.

Tightening torque :

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

When installing the CVVT bolt, hold the hexagonal portion (B) on the camshaft with a wrench to prevent the camshaft from rotating.

2.	Install the intake CVVT & camshaft (A), with the timing mark on the intake CVVT sprocket aligned with the mark (painted link) on the timing chain.

3.	Install the exhaust CVVT (A), with the timing mark on the exhaust CVVT sprocket aligned with the mark (painted link) on the timing chain.

Install the exhaust camshaft (A) to the exhaust CVVT.

Tightening torque :

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

5.	Remove the pick from the service hole in the timing chain cover.

6.	Check that each timing mark of the intake and exhaust CVVT sprockets is aligned as shown in the picture.

Tighten the bolt (A) to the service hole in the timing chain cover.

Tightening torque :

27.5 - 30.4 N·m (2.8 - 3.1 kgf·m, 20.3 - 22.4 lb·ft)

Install the engine mounting support bracket.

(1)

Install the engine mounting support bracket (A).

Tightening torque

Nut (B) :

88.3 - 107.8 N·m (9.0 - 11.0 kgf·m, 65.1 - 79.5 lb·ft)

Bolt and nuts (C) :

58.8 - 73.5 N·m (6.0 - 7.5 kgf·m, 43.4 - 54.2 lb·ft)

(2)

Install the engine ground cable (A).

Tightening torque :

63.7 - 73.5 N·m (6.5 - 7.5 kgf·m, 47.0 - 54.3 lg - ft)

(3)	Remove the jack from the oil pan.

Install the camshaft bearing caps (A) in the order shown in the picture and tighten the bolts to the specified torque.

Tightening torque

M6 bolts :

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

M8 bolts :

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

10.

Install the exhaust oil control valve (OCV) adaptor (A).

Tightening torque :

9.8 - 11.8 N·m (1.0 - 1.2 kgf·m, 7.2 - 8.7 lb·ft)

Check that the front camshaft bearing cap O - ring is properly seated in place when installing the OCV adaptor.

11.	Install the cylinder head cover. (Refer to Cylinder Head Assembly - "Cylinder Head Cover")

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