Variable Camshaft Timing
| ITEM | DESCRIPTION |
|---|---|
| 1 | Variable Camshaft Timing (VCT) solenoid - Intake |
| 2 | VCT actuator - Intake |
| 3 | Secondary timing chain |
| 4 | VCT actuator - Exhaust |
| 5 | VCT solenoid - Exhaust |
The Powertrain Control Module (PCM) controls the system using information from the Camshaft Position (CMP) sensors and the Crankshaft Position (CKP) sensor.
The timing of the intake and exhaust camshafts can be adjusted independently by an oil pressure controlled torsional assist Variable Camshaft Timing (VCT) system. The VCT solenoid that is controlled electrically determines the position of the VCT actuator which has a direct interface with the camshafts.
Each VCT actuator is located on the camshaft at the front of the engine and is secured with a center bolt. Each center bolt contains an oil control valve.
Variable Camshaft Timing Actuator
| ITEM | DESCRIPTION |
|---|---|
| 1 | Solenoid coil |
| 2 | Solenoid core |
| 3 | Variable Camshaft Timing (VCT) solenoid assembly |
| 4 | Solenoid pintle pin |
| 5 | Center bolt |
| 6 | Pressurized engine oil |
| 7 | Filter |
| 8 | Rotor |
| 9 | Variable Camshaft Timing (VCT) actuator assembly |
| 10 | Spool valve |
The Variable Camshaft Timing (VCT) actuators are operated by the VCT solenoids that are controlled by the Powertrain Control Module (PCM). The PCM can operate the VCT solenoids to move the pintle pin to a pre-determined position to control the flow of pressurized engine oil into the VCT actuators.
When advance or retard of the camshaft timing is required
- The VCT solenoid operates,
- Extending the pintle pin,
- And moving the spool valve to direct pressurized engine oil into one side or the other of the central rotor chambers in the VCT actuator.
The solenoid pintle moves towards the spool valve located in the center bolt and makes contact.
Further movement of the solenoid pintle pin will push the spool valve into a known (controlled) position and oil will pass through channels within the center bolt into the VCT actuator chambers. The pressurized engine oil rotates the internal rotor in the VCT actuator which is secured to the camshafts.
This in turn changes the engine timing. The total available camshaft advance adjustment is 50° crankshaft angle towards advance.
Each camshaft VCT actuator has three hydraulic chambers. Residual camshaft torque is used to make sure the VCT actuator is returned to the 'base' position as quickly as possible. The pressurized engine oil is supplied from the variable flow oil pump and must be mapped to deliver a controlled oil pressure to the VCT actuator.