System Description: Description
ECM controls camshaft adjustment according to the following sensors and signals.
- Intake camshaft position sensor
- Exhaust camshaft position sensor
- Engine coolant temperature sensor
- Pressure sensor downstream of throttle valve (Engine load)
- Crankshaft position sensor (Engine speeds)
ECM adjusts camshaft position by controlling intake camshaft actuator and exhaust camshaft actuator according to a PWM signal. ECM continuously adjusts the duty ratio of signal according to the characteristics map consistent with engine load. The control piston of camshaft actuator moves as the magnetic force increases. This allows engine oil to flow into the control plunger. Accordingly, the control plunger moves rearward (axial direction) and rotates each camshaft in the camshaft rotation direction via helical gear. The camshaft position is detected by the intake camshaft position sensor and the exhaust camshaft position sensor and transmitted to ECM as a voltage signal.
ENGINE OIL PRESSURE REGULATION
The engine oil pressure is regulated via the engine oil pump valve in order to ensure an adequate oil supply and to lower the oil pressure if necessary (a saving on fuel)
CAMTRONIC SYSTEM
With the intake camshaft valve lift switchover
, two-stage switchover of the cams occurs on the intake camshaft depending on the characteristics map. The intake valves close earlier due to the switchover of the camshaft to a shorter stroke. This leads to optimization of the throttle lift-off in partial load range. The valve lift switchover to the smaller cam stroke is performed in an rpm range of 1, 000 to 4, 000 rpm. The intake camshaft valve lift switchover actuator is actuated by the ECM by means of a pulse width modulated signal. A coil in the actuator is energized here and a tappet moves in a corresponding curved track on the camshaft. With the turning of the camshaft and the forming of the curved track, the camshaft is moved axially and the smaller cam affects the intake valves. A bump in the curved track has the effect of bringing the tappet back to the default position. To reset the camshaft to the long stroke, a second tappet moves in a corresponding curved track and the reset occurs in the same manner. The position finding of the tappets is over the intake camshaft valve lift switchover position sensor that sends a signal to the ECM for valve lift switchover. For structure and operation, refer to CAMTRONIC System .
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: Tappet |
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: Curved tracks |