Technical data

S_56_A4_Fas09_allr_S_Mod_B 56 27.02.12 11:35
quattro®
quattro is a permanent all-wheel drive system.
If the wheels on one axle of the vehicle lose grip
on the road and threaten to spin, then the drive
force is transferred to the other axle –
automatically and permanently distributed
through the self-locking centre differential with
wheel-selective torque distribution. The basic
distribution is 40 : 60 – 40 % of the drive force
comes from to the front axle, 60 % from the rear.
The benefit is better traction during acceleration
and improved safety due to exceptional grip.
So much for the technology. But what makes
quattro unique is really the driving feel.
“As if you are stuck to the road,” some customers
say. We put it like this: quattro gives you more
feel for the road and thus increased safety.
The quattro with sports differential further
reinforces the unmistakeable quattro feeling.
Vehicles tend to experience understeer when
steering or driving into corners. This is a normal
physical process: A moving object opposes a
change in direction. The elastic tyres and the
suspension mounts tense up until the new
direction has been adopted. When accelerating
into a corner, the load on the front axle is reduced
and it therefore transfers less lateral force to the
tyres – the vehicle understeers. With the sports
differential on the rear axle, the tendency to
understeer is largely counteracted. This is because
the quattro rear axle differential has been
extended left and right by a clutch system with
two gear levels. They ensure that the individual
wheels on the rear axle receive different levels of
torque. The clutches are activated by an electro-
hydraulic actuator. Depending, for example, on
the steering angle, lateral acceleration, yaw angle
and driving speed, the system calculates the right
distribution of wheel torque for any driving
situation. In this way the power is specifically
channelled to the outer rear wheel, when steering
or accelerating into a corner. The effect: the
vehicle is effectively pressed into the corner and
follows the angle of the front wheels.
The fuel consumption and CO₂ emission figures can be found from page 110 onwards.
56
Why only use two wheels
when a car has four?
The quattro® permanent all-wheel drive.
A4_A4_Avant_Fas18_S_2012_03.indd 56 27.03.12 10:14