Engine Speed Sensor: Description and Operation

SPEED AND REFERENCE MARK SENDER, DIGITAL MOTOR ELECTRONICS (DME)
The DME UNIT of the engine is combined with an inductive sender for engine speed and reference mark detection. For this purpose, a toothed ring gear is machined onto the flywheel. This ring has a total of 60 teeth. Two of these teeth are replaced by cutouts to generate the reference mark signal. The reference signal is set at 84° BTDC.

The air gap between the sender and the flywheel ring gear is adjustable and must be 1.0 +/- 0.2 mm (0.040 +/- 0.008 in).