Since 30 years, Audi has been famous for its all-wheel drive technology better known as “quattro”. Quattro is a permanent all-wheel drive system that detects slip when driving (particularly in slippery conditions) and provides additional road grip and safety as required. Over the years, innovation has led to multiple forms and variants of the quattro system.
|Quattro with centre differential||Quattro with multi-plate clutch||Quattro with ultra technology|
Quattro with centre differential
If the wheels of one axle lose grip and threaten to spin, the drive torque is redirected to the other axle – automatically and continuously distributed through the self-locking centre differential with wheel-selective torque control. The basic distribution is 40:60 – with 40% of the power going to the front axle and 60% to the rear. If necessary, however, up to 70% can be directed to the front and up to 85% to the rear to counteract wheel slip.
Quattro with multi-plate clutch
If the wheels on one axle of the vehicle lose grip on the road and threaten to spin, wheel-selective torque control distributes the drive force through the transfer case and hydraulic multi-plate clutch to the axle or individual wheel with the better grip.
The electronically controlled multi-plate clutch is mounted on the end of the prop shaft and is supplied with oil from an electric pump.
Quattro with ultra technology
Quattro with ultra technology combines driving dynamics with efficiency and helps to cut consumption by up to 0.3 l/100 km. By switching between four-wheel drive and the more efficient front-wheel drive, four-wheel drive is used whenever the driving situation calls for it. The predictive operating strategy activates quattro within a matter of milliseconds.
How does it work?
The gain in efficiency is enabled by two clutches in the drivetrain. These are arranged so that the rear portion of the drivetrain can be completely decoupled. Thanks to the interaction of these clutches with an intelligent operating strategy, quattro with ultra technology offers all the advantages of front-wheel drive when the driving conditions do not require all-wheel drive. To this end, a clutch on the gearbox decouples the propshaft from the rear wheels. An integrated decoupler opens on the rear-axle differential. This cuts out the main cause of drag losses on the rear drivetrain. So, for example, fuel can be saved when driving at a constant speed on the motorway in good weather conditions. To switch on the all-wheel drive, the stationary propshaft can be accelerated to the necessary speed within fractions of a second, and both clutches can be closed again. Consequently, the quattro drive is always ready: before it is needed and without the switch being perceived by the driver.
The intelligent control of the all-wheel drive works predictively, i.e. using extensive sensors and continual analysis of the ascertained data on driving dynamics, road conditions and driver behaviour, it looks into the future, about half a second ahead. However, it only takes a few fractions of a second to switch on the all-wheel drive. If a driving situation cannot be predicted, for example if the wheels move from dry tarmac to a sheet of ice, the system will react imperceptibly to the sudden change in the coefficient of friction.