Audi has just revealed a new variation of its quattro all-wheel drive system with ‘ultra’ technology. Key features of the system include the ability to go from all-wheel to front-wheel drive and back again, depending on the conditions. The ultra tag also signifies better fuel efficiency – it consumes 0.3 litres per km less than conventional all-wheel drive.
As to how it works, there are two clutches in the drivetrain. A switch to front-wheel drive will see the front clutch (multi-plate clutch behind the transmission) disconnecting the propshaft. At the same time, an integrated decoupler in the rear-axle differential also opens, to shut down the main cause of drag loss in the rear
To go back into all-wheel drive mode, only requires 250 milliseconds or 0.25 seconds. Here, the decoupled stationary components are accelerated in fractions of a second through the multi-plate clutch, which will mechanically close the decoupler on the axle differential, hence bringing the rear back into action.
Audi says that all-wheel drive will be deactivated when it is not in need, but it is always available. Furthermore, when it is eventually required, the system is activated even before the driver needs it. As the quattro electronics are networked, the system retrieves and analyses data such as steering angle, lateral and longitudinal acceleration, engine torque and more every ten milliseconds.
Activation of the all-wheel drive follows a three-stage strategy: a proactive activation, based on data delivered via the network; predictive activation, based on the driver’s style, status of the ESC, the drive select mode, and the trailer detection system; and reactive activation, which takes place when there’s a sudden change in friction, like when on ice or suddenly going pedal-to-the-metal round corners.
Currently, models that wear the ultra badge have all been front-wheel drive variants. This will soon change with the new quattro ultra system, starting with the B9 Audi A4 Allroad, which will debut in the second quarter of 2016. It will subsequently make its way into other models with longitudinally mounted front engines, Audi says.
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