New Audi Quattro Technology Selectively Applies All-Wheel Drive

Audi AG’s new "quattro ultra" system allows vehicles to combine the efficiency of front-wheel-drive layouts with the added traction of all-wheel drive.

The current Quattro system is on at all times, even when power isn’t being directed to the rear wheels. The new system, which completely disengages the rear-wheel drive when it’s not needed, will debut later this year on the new A4 Allroad compact wagon. Audi says tests show that vehicles using the system consumed an average of 0.3 liters per 100 km (0.6 gallons/62 miles) less fuel than conventional awd cars and showed no loss of performance.

Traditional awd system uses Torsen sensing to measure existing traction levels and apply torque accordingly, but Audi’s the new system uses a variety of inputs. Every 10 milliseconds, sensors measure longitudinal acceleration, engine torque, steering angle, yaw rate and road traction. Based on this information, the new system can activate awd about a half second before it is needed to prevent wheel slip—or virtually instantaneously upon a sudden loss of traction, such as when driving over an ice patch.

Predictive algorithms activate awd based on driving style, pre-selected driving mode, the status of the vehicle’s electronic stability control, input from the trailer detection system and GPS information about the upcoming road. During aggressive driving on winding roads, the system keeps the rear wheels engaged at all times.

The ultra system uses an electro-mechanically operated multi-plate front clutch, rear gear and decoupling system in place of the central/rear differential hardware Audi has used since it launched its quattro awd system in 1980. Audi says the new system is about 9 lbs lighter than its current quattro unit.

Mounted on the end of a 7-speed dual-clutch transmission, the front clutch rotates as many as seven plates through an oil bath. AWD is activated when the plates are pressed together, varying torque distribution between the front and rear axles based on the contact pressure of the plates.

In fwd-only mode, the multi-plate clutch disconnects the propshaft. The decoupler within the rear differential also opens. This cuts torque to the rear axle and reduces friction and associated drag losses, Audi notes. The only rwd components engaged at this point are the bevel gears within the axle and gears within the differential, which compensate for differences in wheel rotation speed during cornering.

The new system also includes vectoring capability to vary torque levels between the left and right wheels based on input from a car’s antilock brake system and electronic stability control.

Following the A4, Audi plans to expand the quattro ultra system to other vehicles built on its Modular Longitudinal Architecture, such as the A5 coupe and Q5 crossover vehicle. Traditional Torsen-based quattro awd will continue to be used on larger vehicles and high-performance models.