Kia Forte BD Quiz
Engine Mechanical System

CVVT and Camshaft

In this manual: Engine Mechanical System
General Information — 8Maintenance — 32Engine Mechanical System — 47Engine Electrical System — 17Emission Control System — 10Engine Control System/Fuel System — 32Clutch System — 11Manual Transmission — 11DCT (Dual Clutch Transmission) System — 16Drive Shaft and Axle — 8Suspension System — 26Steering — 9Restraints — 11Brake System — 27Body (Interior and Exterior) — 119Body Electrical System — 98Heating, Ventilation, and Air Conditioning — 27
26steps
~156min
4/5difficulty
0102030405013.710N·mlb·ft
Tightening torque found on this page
Done 0 of 26

Components and Component 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

The Continuously Variable Valve Timing (CVVT) system advances or retards the intake and exhaust valve timing according to the control signal from the ECM, which is calculated based on engine speed and load.

CVVT control provides valve overlap or underlap, which improves fuel economy and reduces exhaust emissions (NOx, HC) and improves engine performance by reducing pumping losses, internal exhaust gas recirculation 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 to the cam phaser or drains engine oil from the cam phaser according to the ECM PWM (Pulse Width Modulation) control signal,

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

  • and Cam Phaser, which changes the cam phase by hydraulic force of engine oil.

Engine oil flowing from the CVVT oil control valve changes the camshaft phase in the advance direction (intake advance / exhaust retard) or in the opposite direction (intake retard / exhaust advance) relative to engine rotation, by rotating the rotor connected to the camshaft inside the cam phaser.

Operating Principle

CVVT has a mechanism that rotates the rotor vane with hydraulic pressure generated by engine oil supplied to the advance or retard chamber according to the CVVT oil control valve control.

[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		 Fully
Advance		 * Lower valve overlap
* Improved combustion stability		 Fully
Retard		 * Lower valve overlap
* Improved combustion stability
(2) Partial Load Retard * Increased expansion work
* Reduced pumping losses
* Reduced HC		 Retard * Reduced pumping losses
(3) Low Speed
/High Load		 Retard * Increased expansion work Advance * Prevents intake backflow (improves volumetric efficiency)
(4) High Speed
/High Load		 Advance * Reduced pumping losses Retard * Improved volumetric efficiency

Repair Procedures

Removal

  1. Remove the cylinder head cover.

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

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

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

    2. Make sure the TDC alignment marks on the intake and exhaust CVVT sprockets are in a straight line with the cylinder head surface, as shown in the illustration. If not, turn the crankshaft damper pulley one full revolution (360°).

    3. Mark the timing chain links with white paint marker to match the timing marks on the CVVT sprockets.

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

  4. Remove the camshaft bearing caps (A) in the order shown in the illustration below.

  5. Remove the engine mount support bracket.

    1. Place a jack under the oil pan.

    2. Disconnect the engine ground cable (A).

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

    4. Raise the engine slightly with a jack to create space to release the timing chain tensioner.

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

  7. Lock the timing chain tensioner in the fully retracted position.

    1. Insert a pick tool into the service hole in the timing chain cover and lift the left-side hole of the ratchet plate (A) on the tensioner so that the pawl (B, located inside the tensioner behind the ratchet plate) rises.

    2. With the pawl raised, ask an assistant to lift the exhaust CVVT and camshaft (A) to allow the tensioner plunger (B) to retract.

    3. When the tensioner plunger is fully retracted, lift the left-side hole of the ratchet plate (A) again through the service hole in the chain cover to align the plate hole with the hole in the tensioner housing behind the ratchet plate, then lock the tensioner by inserting a pick tool through the ratchet plate and housing 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 and camshaft (A).

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

Inspection

Camshaft

  1. Measure the cam lobe height with a micrometer and inspect the cam lobe surface for wear. Replace the camshaft if necessary.

    Cam lobe height Intake: 44.15 mm (1.738 in) Exhaust: 43.55 mm (1.715 in)

  2. Inspect the camshaft journal surface for wear. If the camshaft journal is excessively damaged, replace the camshaft.

  3. Inspect the camshaft journal oil clearance.

    1. Clean the camshaft journals and bearing caps.

    2. Place the camshafts on the cylinder head.

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

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

      Tightening Torque

      M6 bolts:

      11,8–13.7 N·m

      M8 bolts:

      18,6–23 N·m

    5. Remove the bearing caps.

    6. Measure the Plastigage at its widest point. If the clearance is greater than specified, replace the camshaft. If necessary, replace the bearing caps and 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)

  4. Inspect the camshaft end play.

    1. Inspect the camshaft end play.

    2. Measure the camshaft end play by moving the camshaft forward and backward using a dial indicator. If the end play is greater than specified, replace the camshaft. If necessary, replace the bearing caps and 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

  1. Inspect the CVVT for smooth rotation.

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

    2. Make sure the CVVT is locked by turning it clockwise or counterclockwise. It should 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 holes in the camshaft journal with tape.

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

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

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

      Exhaust CVVT: While applying compressed air, turn the CVVT in the retard direction (clockwise), and make sure the CVVT rotates smoothly.

      CVVT phase range

      Intake: 25° ± 1° (from most retarded position to most advanced position)

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

    6. Intake CVVT: Turn the CVVT to the most retarded position (clockwise), then make sure the CVVT is locked.

      Exhaust CVVT: Turn the CVVT to the most advanced position (counterclockwise), then make sure the CVVT is locked.

Installation

  1. Install the intake CVVT (A) onto the intake camshaft.

    Tightening torque: 63.7–74 N·m

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

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

  4. Install the exhaust camshaft (A) onto the exhaust CVVT.

    Tightening torque: 63.7–74 N·m

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

  6. Make sure that each alignment mark on the intake and exhaust CVVT sprockets is aligned, as shown in the illustration.

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

    Tightening torque: 27.5 - 30 N·m

  8. Install the engine mount bracket.

    1. Install the engine mount bracket (A).

      Tightening Torque

      Nut (B):

      88,3–108 N·m

      Bolt and nuts (C):

      58,8–74 N·m

    2. Install the engine ground cable (A).

      Tightening torque: 63.7–74 N·m

    3. Remove the jack from the oil pan.

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

    Tightening Torque

    M6 bolts:

    11,8–13.7 N·m

    M8 bolts:

    18,6–23 N·m

  10. Install the exhaust oil control valve (OCV) adapter (A).

    Tightening Torque: 9.8–11.8 N·m

  11. Install the cylinder head cover.

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

Test yourself

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