Motec SDC1 Diff Controller Impreza 2003 WRX & STi

Functionality

The SDC units are used to adjust the torque split between the front and rear differentials to achieve greater control over handling characteristics such as traction, braking on loose surfaces, turn in response, and understeer on both corner entry and exit.

The centre differential is essentially a limited slip differential with adjustable preload. The SDCs work by regulating solenoid current, which is proportional to the preload. When no current is applied (0% lock) the centre differential operates as an 'open diff' with a mechanical torque distribution of 65% rear and 35% front (60% and 40% in some vehicles). With increasing current (increasing percentage lock) the preload increases, requiring more torque difference between front and rear wheels before the centre differential will slip.

There are six selectable control modes: 0% lock, 100% lock and four user-configurable modes. These modes can be selected using the DCCD thumb wheel.