Variable Camshaft Timing Operation
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When the engine is running, the compression and expansion of the valve springs causes momentary increases and decreases in the torque acting on the camshafts. These momentary changes of torque are sensed in the VCT units and used to change the camshaft timing.
| ITEM | DESCRIPTION |
|---|---|
| A | Camshaft torque |
| B | Camshaft rotation (degrees) |
| C | Valve opening |
| D | Peak lift |
| E | Valve closing |
| 1 | 1000 rev/min |
| 2 | 4000 rev/min |
| 3 | 7000 rev/min |
| 4 | Inertia effects from valve train rotating components |
| 5 | Force caused by valve spring |
| 6 | Bias torque from friction |
NOTE:
Intake camshaft VCT unit shown. For exhaust camshaft VCT unit, read advance for retard and retard for advance.