Camshaft Position Actuator System Operation
A CMP actuator dynamically changes valve timing events relative to piston timing by controlling camshaft position. This is sometimes referred to as variable valve timing or camshaft phasing. Variable valve timing or camshaft phasing does not change duration or lift.
- By advancing camshaft timing, an improvement in low end torque can be achieved.
- By retarding camshaft timing slightly, an improvement in high end power can be achieved.
- By retarding camshaft timing significantly, an improvement in light load fuel economy can be achieved.
There are 5 cavities divided by vanes within the CMP actuator.
- When oil is directed to the advance cavities (1), the camshaft timing is advanced.
- When oil is directed to the retard cavities (2), the camshaft timing is retarded.
- When oil is directed to both cavities, the camshaft is held stationary.
The CMP actuator (1) has a 62 degree (a) range of authority at the crankshaft (31 degrees (d) at the camshaft). With the engine not running and no engine oil pressure to the CMP actuator (1), the high tension spring positions camshaft timing at the 7 degree (c) advanced park position at the crankshaft (3.5 degrees (f) at the camshaft). During normal engine operation, and based on performance requirements, the ECM may adjust camshaft timing, as required, within a range from 7 degrees (c) advanced at the crankshaft (3.5 degrees (f) at the camshaft) to 55 degrees (b) retard at the crankshaft (27.5 degrees (e) at the camshaft).