Variable Camshaft Timing Components
| ITEM | DESCRIPTION |
|---|---|
| 1 | Intake Variable Camshaft Timing (VCT) actuator assembly |
| 2 | Exhaust VCT actuator assembly |
| 3 | Exhaust VCT solenoid |
| 4 | Camshaft Position (CMP) sensors |
| 5 | Intake VCT solenoid |
The timing of the intake and exhaust camshafts can be adjusted independently by an electro-hydraulic controlled Variable Camshaft Timing (VCT) system. The Powertrain Control Module (PCM) controls the system using information from the Camshaft Position (CMP) sensors and the Crankshaft Position (CKP) sensor.
The VCT system varies the timing of the intake and exhaust camshafts to deliver optimum engine power, efficiency and emissions. The timing of the intake camshafts has a range of 62° of crankshaft angle. The timing of the exhaust camshafts has a range of 50° of crankshaft angle.
In the base timing position:
- The intake camshafts are fully retarded.
- The exhaust camshafts are fully advanced.
| CAMSHAFT | VALVE OPENS | VALVE CLOSES |
|---|---|---|
| Intake | 29° Before Top Dead Center (BTDC) to 33° After Top Dead Center (ATDC) | 207° to 269° ATDC |
| Exhaust | 244° to 194° BTDC | 6° to 56° ATDC |
The system consists of a VCT actuator and a VCT solenoid for each camshaft. The PCM controls the system using Pulse Width Modulation (PWM) signals to the VCT solenoids.
The torsional energy generated by the valve springs and the inertia of the valve train components are used to operate the system.
Variable Camshaft Timing Actuators
| ITEM | DESCRIPTION |
|---|---|
| 1 | Bolt (quantity 3) |
| 2 | Variable Camshaft Timing (VCT) actuator |
| 3 | Filter |
| 4 | Camshaft |
| 5 | Inner plate |
| 6 | Housing and sprocket |
| 7 | Rotor assembly |
| 8 | Reed plate |
| 9 | Spring and lock pin |
| 10 | Spring (quantity 3) |
| 11 | Tip seal (quantity 3) |
| 12 | Spring (quantity 2) |
| 13 | Tip seal (quantity 2) |
| 14 | Spring |
| 15 | Dowel pin |
| 16 | Bias spring |
| 17 | Snap ring |
| 18 | Sensor wheel |
| 19 | Center plate |
| 20 | Snap ring |
| 21 | Bolt (6) |
| 22 | Spool valve |
| 23 | Outer plate |
The VCT actuators change the position of the camshafts in relation to the timing chains.
Each VCT actuator is attached to the camshaft by 3 bolts. A rotor assembly and a reed plate are installed inside a sprocket housing. The sprocket housing consists of a sprocket, an outer plate and an inner plate held together by 6 bolts.
The sensor wheel for the CMP sensor, the center plate and the bias spring are installed at the front of the VCT actuator. The ends of the bias spring locate on the center plate assembly and the sprocket housing. This is to give a turning moment to the camshaft in the advance direction. A snap ring locates the sensor wheel onto a sleeve installed in the center of the rotor assembly. The opposite end of the sleeve locates in a bore in the front face of the camshaft, which contains a filter.
A spring and spool valve are installed in the rotor assembly sleeve and retained by a snap ring. The spring keeps the spool valve in contact with the armature of the related VCT solenoid.
Each VCT actuator is supplied with engine oil from an oil gallery in the cylinder head. The engine oil flows through the camshaft front bearing cap and a bore in the center of the camshaft.
Variable Camshaft Timing Solenoids
The VCT solenoids control the position of the spool valves in the VCT actuators.
The VCT solenoids are installed in the front upper timing covers, immediately in front of their related VCT actuators. Each VCT solenoid is secured with 2 bolts and sealed with an O-ring seal. The electrical connector provides the interface with the wiring harness.
Each VCT solenoid incorporates a spindle that acts on the spool valve in the related VCT actuator to advance and retard the camshaft timing. The VCT solenoids operate independently and are controlled by a PWM signal from the PCM.