Those who know Audi know quattro. And once you have driven with the permanent four-wheel drive system from Audi you don’t want to drive any other way. Why? Because practically no other drive system transfers engine power so directly to the road.
The latest generation of quattro permanent four-wheel drive is employed on the RS models in the A4 and A5 model lines. Its key component is the self-locking crown-gear centre differential, which uses plate packages to achieve high locking values for further enhanced traction. Furthermore, compared with the construction method used previously, this centre differential is lighter and requires less installation space. The basic asymmetric torque distribution of 40:60 (front axle : rear axle) is maintained for the benefit of the driving dynamics; however, if required, a higher proportion of torque can now be directed to the front or rear axle.
In conjunction with torque vectoring, this allows the drive force to be distributed individually to each wheel as the driving situation dictates. What makes this special is that torque distribution takes effect before any undesirable wheel slip occurs. In this way, a yawing moment can be generated which assists cornering.
The crown-gear differential surpasses its predecessors due to the wide range of torque distribution.
All this results in precise control and sporty handling as well as enhanced agility along with outstanding traction.
As an option, the quattro driveline with torque vectoring can be supplemented by the sport differential on the rear axle.
This tendency is largely counteracted with the sport differential on the rear axle. This is because a superposition unit with two gear stages has been added to the quattro rear-axle differential on the left and right. These ensure that the individual wheels on the rear axle receive different levels of drive torque. The clutches are activated by an electrohydraulic actuator. Depending on factors such as steering angle, lateral acceleration, yaw angle and road speed, the control unit calculates the most suitable distribution of torque to the wheels for every driving situation. When the steering wheel is turned, for example, or the car accelerated in a bend, power is redirected specifically to the outer rear wheel.
This has the effect of pushing the car into the bend so that it follows the angle of the front wheels. The difference in tractive force between the left and right wheels exerts an additional steering effect, so that the corrections the driver has previously had to make to the steering wheel become virtually unnecessary. This allows precise control and sporty handling as well as greater agility along with outstanding traction.