Differential Electronic Module (DEM) (2008): Function: PRETENSIONING

The function of the four wheel drive system is based on there being a speed (RPM) difference between the front wheels and the rear wheels. This speed (RPM) difference can affect torque performance in certain driving situations. The task of the pre-tensioning function is to improve torque performance, in particular when pulling off from being stationary, without affecting other properties in the system.

The pre-tensioning function is achieved by the electric feed pump starting as soon as the engine has started. During acceleration, when pulling off, or during other situations that means that the oil pressure's desired value is not achieved by the clutch's flow, the feed pump, together with the check and by-pass valve, builds up a pressure (1.0 MPa). This pressure affects the clutch driven plates and can therefore transfer greater torque to the rear axle. The pre-tensioning function is controlled by the software so that activation only occurs when necessary.