The primary model of Audi’s quattro featured three mechanical differentials — entrance, middle, and rear — with the choice to lock the middle differential with a vacuum system. This resulted in a 50-50 torque cut up between the entrance and rear. Within the Nineteen Eighties, Audi changed the middle differential with a Torsen (or torque-sensing) differential, permitting torque to be directed to the wheel with traction as an alternative of spinning the wheel with out.
An everyday open differential permits the wheels in an axle to spin at completely different charges, which is nice if you have to make tight turns, however for conditions the place you do not have traction, it ends in the wheel spinning aimlessly. To enhance grip, Audi saved a rear locking differential when it added the Torsen to its quattro system. The change to a Torsen and rear locking differential meant that as much as two thirds of torque might be despatched to both axle when wanted.
Audi actually started to modernize its AWD system with the introduction of the transverse-engine Audi TT within the 12 months 2000. The corporate switched out the Torsen middle differential with a hydraulically-controlled, clutch-operated Haldex coupling, splitting energy between the entrance and the rear.
This meant that the Audi TT was front-wheel-biased till it misplaced traction, distributing extra of the torque to the rear axle to compensate. As well as, the TT additionally launched EDL (digital differential lock) that used the ABS system to distribute torque on a per-wheel foundation.