Description And Operation: Engine: Description: Camshafts
| ITEM | DESCRIPTION |
|---|---|
| 1 | Intake camshaft |
| 2 | Needle roller bearings |
| 3 | Intake camshaft lobe (4 off) |
| 4 | Reluctor ring - Camshaft Position (CMP) sensor |
| 5 | Exhaust camshaft lobe (8 off) |
| 6 | Lobe - High Pressure (HP) fuel pump |
| 7 | Exhaust camshaft |
The engine is fitted with a Double Over Head Camshaft (DOHC) configuration which uses two camshafts:
- One intake camshaft
- One exhaust camshaft.
The lobes on the exhaust camshaft control the opening and closing of the exhaust valves via the roller finger cam followers. There is one lobe that drives the High Pressure (HP) fuel pump.
The lobes on the intake camshaft control the opening and closing of the intake valves via the Continuously Variable Valve Lift (CVVL) assembly.
The camshafts run on needle roller bearings to reduce friction and minimize the breakaway torque on engine startup. The needle roller bearings are housed in the camshaft carrier and the camshaft caps are marked with 'I' and 'E' to denote inlet and exhaust. The camshaft caps are also numbered to make sure assembly in the correct position in the camshaft carrier. For example 'I4' or 'E1'.
The camshafts are of a hollow steel tube construction, with pressed on forged lobes and needle roller bearings. The hollow tube design provides reduced weight for increased engine performance. Each camshaft has a pressed on drive adapter which locates a drive sprocket and the Variable Camshaft Timing (VCT) actuator. Each drive adapter is equipped with a timing pin to locate the drive sprocket and the VCT actuator on the camshaft relative to the lobe positions. Each camshaft has a pressed on reluctor ring for use with the Camshaft Position (CMP) sensors.
The VCT actuator contains a sprocket which drives the camshaft via a timing chain, driven from the crankshaft. The VCT actuator adjusts the timing of both camshafts, increasing engine efficiency and performance as required. The reluctor wheels are pressed on to the opposite end of the exhaust camshafts which are monitored by the CMP sensor. The CMP sensor signal is used by the Powertrain Control Module (PCM) and enables the PCM to determine the position of the camshafts. The camshafts can then be phased by the VCT actuators to provide increased performance and efficiency.