As the 1970s drew to a close, two efforts were taking place on parallel but independent courses in then-West Germany that would fundamentally transform how drivers approached their craft, especially in bad weather. On one such track, Daimler-Benz was working closely in conjunction with Robert Bosch AG to develop equipment that would maintain steering control during conditions of limited traction, a process that led to the first workable antilock braking systems for road vehicles. Elsewhere, Audi was planning a new technology that would allow it conquer the frantic world of European performance rallying, while transforming its entire lineup into something it had never been, a range of performance cars with all-weather capability. That was the origin of Audi’s quattro all-wheel-drive system. It was first proven by demonstrations of driving up, not down, ski jumps and mogul runs under full throttle. When it became part of the original Sport Quattro coupe, especially in the hands of rally icon Walter Rohrl, the quattro (lower-case “q” when referring to the system) tech instantly transformed Audi into an unstoppable force in the World Rally Championship, a journey that also say it lock up a slew of Le Mans overall wins with the unbeatable combination of quattro grip and turbocharged diesel power.
The quattro system, a landmark leap forward in the world of vehicle dynamics, turns 40 this year. Audi is one of two global automakers, the other being Subaru, whose products are now defined by superior traction under the worst weather conditions imaginable. The quattro system’s evolution has been the story of its adaptation to advancing vehicle platforms as they’ve progressed from longtitudinal to transverse powertrain orientation. The original ur-Quattro, as the car is known today, had a longitudinally mounted, turbocharged inline-five for power, backed by a conventionally located transmission. This first quattro generation used a trio of differentials to distribute power: One for the front wheels, one for the wheels in the back, and a manually operated center differential that distributed power between both ends of the car as traction conditions dictated. The system’s first major upgrade came in the late 1980s, when Audi adopted the Gleason Torsen center differential, which operated automatically and instantly delivered a 50-50 torque split between the front and rear wheels. When Audi introduced its bite-sized TT sport coupe in 2000, which had a transverse engine between the front wheels, there was no longer any room to mounted the Torsen. Audi reached out to Haldex Traction AB of Sweden, now an operating unit of BorgWarner, which provided its hydraulic-mechanical Haldex coupling for installation just ahead of the TT’s quattro rear differential. The Haldex coupling received power from a propshaft running aft from the TT’s front transaxle. Electronic sensors detecting engine speed, torque and throttle position allowed the coupling to distribute power front to rear. Today’s Audi lineup utilizes no less than five variations of that quattro system, adapted to match the varying platforms on which its vehicles are built, including the e-tron electrics with traction motors on each axle. Current quattro setups are both mechanically and electronically controlled, with additional sensors being employed that now monitor steering angle, stability control, yaw and wheel movements. Default power distribution is now 40-60 front to rear, although the system can make adjustments ranging from 70 percent of power to the front to 85 percent at the rear as conditions necessitate. It’s fair to say that a lot of Audi owners were able to drive their way out of serious trouble since the quattro system was introduced. That adds up to a lot of saved lives. Audi deserves congratulations for that.
Jim Donnelly On Wheels 