911 Carrera 4S Coupe AWD F6-3600cc 3.6L SOHC (1997)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
PURPOSE
A twin coil positioner is used to adjust the correct engine idle speed of 800 +/- 40 rpm in conjunction with the Digital Motor Electronics (DME)
control unit. The cold engine idle speed is approx. 1,100 rpm.
OPERATION
The positioner is supplied with two clocked electrical input signals from the DME control unit, one for the opening coil and the other for the closing
coil. This creates opposed torsional forces on the armature. Due to the inertia of the armature, the positioner adjusts itself to a particular angle that
corresponds to the pulse/duty factor of the signal received.
By modifying the input signals, e.g. when the engine speed changes, the pulse/duty factor of the signal supplied to the positioner changes as well. The
programmed nominal rpm is compared with the actual revolution speed in the control unit. The air flow is then modified by the positioner until the
nominal rpm and the actual rpm are identical.
