CVVT and Camshaft

Description and Operation

Description

Continuously Variable Valve Timing (CVVT) controls the intake and exhaust valve timing toward "advance" or "retard" according to the control signal from the ECM, which is calculated based on engine speed and load.

With Continuously Variable Valve Timing (CVVT), changing the valve overlap reduces fuel consumption and harmful emissions (NOx, HC). In addition, engine performance is improved by reducing pumping loss, providing an internal EGR effect, improving combustion stability, improving volumetric efficiency and increasing expansion work.

This system consists of the following:

• CVVT oil control valve (OCV), which supplies engine oil pressure to the cam phaser or regulates it by PWM (Pulse Width Modulation) in accordance with the control signal from the ECM, allowing the cam phaser to operate,

• CVVT oil temperature sensor (OTS), which measures the engine oil temperature,

• and cam phaser, which adjusts the camshaft phase in accordance with the oil pressure supplied. Hydraulic force varies.

Engine oil flowing through the CVVT oil control valve moves the camshaft in the advance direction (intake advance / exhaust retard) or in the reverse direction (intake retard / exhaust advance) relative to engine rotation by rotating the rotor connected to the camshaft in the cam phaser.

OPERATING PRINCIPLE

The CVVT uses a hydraulic mechanism in which the vane rotates by the pressure of engine oil. The oil supply to the chambers that advances or retards the phase is controlled by the CVVT oil control valve.

[CVVT System Mode]

(1) Low speed / low load	(2) Partial load
(3) Low speed / high load	(4) High speed / high load

repair procedures

expansion

1. 1

   Remove the cylinder head cover.

   (Refer to Cylinder Head - "Cylinder Head Cover")

2. 2

   Remove the vacuum pump.

   (Refer to Cylinder Head - "Vacuum Pump")

3. 3

   Remove timing chain.

   (Refer to Ignition System - "Timing Chain")

4. 4

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

   

5. 5

   Remove the front camshaft bearing cap (A) and center camshaft bearing cap (B). Remove the camshaft in the order shown.

   

   

6. 6

   Remove the camshafts (A).

   

TEST

Camshaft

1. 1

   Inspect the camshaft lobes.

   Measure the cam height with a micrometer.

   CAM HEIGHT Intake: 41.79824 mm Exhaust: 41.57000 mm

   

   Replace the camshaft if the cam height is less than standard.

2. 2

   Inspect the camshaft bearing clearance.

   1. Clean the camshaft bearing caps and journals.

   2. Install the camshafts on the cylinder head.

   3. Place a strip of Plastigage on each camshaft journal.

      

   4. Install the front camshaft bearing cap (A), center camshaft bearing cap (B) and rear camshaft bearing cap (C) as follows, and tighten to the specified torque.

      Tightening torque:

      STEP 1

      A: 9.8 N·m

      B: 5.9 N·m

      STEP 2

      A: 18.6~23 N·m

      B: 11.8~13.7 N·m

      C: 11,8~13.7 N·m

      

      

   5. Remove the bearing cap.

   6. Measure the Plastigage at its widest point.

      Camshaft bearing clearance

      Intake:

      0.027~0.057 mm

      Exhaust:

      0.027~0.057 mm

      

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

   7. Completely remove the Plastigage.

   (8th)

   Remove the camshaft.

3. 3

   Inspect the camshaft end play.

   1. Install the camshaft (A).

      

   2. Install the front camshaft bearing cap (A), center camshaft bearing cap (B) and rear camshaft bearing cap (C) as follows, and tighten to the specified torque.

      Tightening torque:

      STEP 1

      A: 9.8 N·m

      B: 5.9 N·m

      STEP 2

      A: 18.6~23 N·m

      B: 11.8~13.7 N·m

      C: 11,8~13.7 N·m

      

      

   3. Move the camshaft back and forth in the longitudinal direction. Measure the axial play with a dial indicator.

      Camshaft axial play: Intake: 0.1~0.2 mm Exhaust: 0.1~0.2 mm

      

      Replace the camshaft if the axial play is greater than the maximum. If necessary, replace the cylinder head.

   4. Remove the camshafts.

CVVT (Continuously Variable Valve Timing)

1. Inspect CVVT.

   1. Clamp the camshaft in a vise. Make sure the cams and pins in the vise are not damaged.

   2. Make sure the CVVT is locked. It should not rotate.

   3. Intake CVVT: Seal one of the first two holes in the camshaft journal with tape.

      Exhaust CVVT: Seal one of the last two holes in the camshaft journal with tape.

      [Intake]

      

      [Exhaust]

      

   4. Intake CVVT: Apply compressed air of approximately 150 kPa (1.5 kgf/cm²) to the unsealed advance hole to release the lock.

      Exhaust CVVT: Apply compressed air of approximately 150 kPa (1.5 kgf/cm²) to the unsealed retard hole to release the lock.

   5. Intake CVVT: While applying compressed air, rotate the CVVT within its phase range in the advance direction (counterclockwise), and make sure the CVVT rotates smoothly.

      Exhaust CVVT: When applying compressed air, the CVVT is in the retard direction (clockwise), and check that the CVVT moves smoothly. Rotate.

      

      CVVT phase range

      Intake:

      25° (from maximum retard to maximum advance position)

      Exhaust:

      20° (from maximum advance position to maximum retard position)

   6. Intake CVVT: Rotate the CVVT to the maximum retard position (clockwise) and check whether the CVVT is locked.

      Exhaust CVVT: Rotate the CVVT to the maximum advance position (counterclockwise) and check whether the CVVT is locked.

Installation

1. 1

   Install the camshafts (A).

   

2. 2

   Front camshaft bearing cap (A) and center camshaft bearing cap (B). Install the camshaft bearing caps in the sequence shown.

   Tightening torque:

   STEP 1

   A: 9.8 N·m

   B: 5.9 N·m

   STEP 2

   A: 18.6~23 N·m

   B: 11.8~13.7 N·m

   C: 11,8~13.7 N·m

   

   

3. 3

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

   Tightening torque: 63.7~74 N·m

   

4. 4

   Install the remaining parts in the reverse order of removal.