Ready at all times: quattro all-wheel drive in two versions

Ready at all times: quattro all-wheel drive in two versions

An ultimate plus in dynamics, traction, driving safety and straight-line tracking – the quattro all-wheel drive from Audi has been guaranteeing this for over three decades. Now Audi is taking the next big step as quattro with ultra technology makes its debut in the new A4 allroad quattro* 2.0 TFSI.

For the future: quattro with ultra technology
quattro with ultra technology is an all-wheel drive system optimized for efficiency with no discernible differences compared with permanent systems in terms of traction and handling. These requirements, which may at first glance appear irreconcilable, are fulfilled by the interplay of the newly developed all-wheel drive components and an ingenious operating strategy. The all-wheel drive system’s intelligent control works predictively, always looking ahead with its comprehensive array of sensors and continually analyzing data on vehicle dynamics, road condition and driver behavior. In standard operation at low loads, when there is no risk of wheel slip, the new quattro taps into all the advantages of front-wheel drive, but is always ready to engage all-wheel drive when it is needed. This system significantly reduces the potential difference in fuel consumption between front-wheel drive and permanent all-wheel drive systems.

Operating strategy
The quattro electronics are networked with a number of other control units. Every ten milliseconds, the system acquires and analyzes a wide variety of data, such as steering angle, lateral and longitudinal acceleration and engine torque to name just a few. Activation of the all-wheel drive system follows a two-stage strategy: predictive, i.e. anticipatory, and reactive.

On the predictive level, the focus is on data supplied by the networked systems in the car. The control unit uses these data to, for example, compute the point when the inside front tire will reach the limit of grip during fast cornering. The calculation is completed roughly 0.5 seconds prior. If the wheel approaches the limit of grip within a defined threshold, the all-wheel drive system is activated. With predictive activation, the quattro control unit is primarily oriented towards the driver’s style of driving, the status of the ESC and the mode selected in the Audi drive select system and trailer detection. In the seldomly occurring reactive activation, the system is reacting to sudden changes in road friction. These might occur, for example, when the wheels go from dry asphalt to a sheet of ice.

By networking quattro drive with Audi drive select, drivers can adjust all-wheel-drive properties to suit their individual preferences. The auto mode in drive select provides the best possible traction and balanced handling. In dynamic mode, power is redistributed to the rear axle sooner and to a larger degree, improving handling, particularly at low coefficients of friction. In the offroad setting, the all-wheel drive system is always engaged.

Technology: two clutches
The special layout of two clutches in the drivetrain enables a crucial gain in efficiency. When the system switches over to front-wheel drive, the front clutch – a multi-plate clutch at the transmission takeoff – decouples the propshaft. An integrated decoupling clutch also opens in the rear differential. This eliminates the main sources of drag-torque losses in the rear part of the drivetrain – such as the differential drive gear turning in the oil bath. The quattro drivetrain is also nearly four kilograms (8.8 lb) lighter than the previous system despite the new technical components. That, too, saves fuel and benefits handling.

Heart of the matter: limited-slip center differential
The permanent quattro all-wheel drive system will continue to be used with all TDI engines of the new Audi A4 allroad quattro*. It operates purely mechanically. During normal driving, its limited-slip center differential, designed as a planetary gear wheel, distributes 60 percent of engine torque to the rear wheels and 40 percent to the front. When it redistributes these forces, as much as 85 percent can be directed to the rear and up to 70 percent to the front. These high locking figures enable a clearly defined torque distribution and extremely precise interplay with control systems.

quattro drive is partnered with the updated wheel-selective torque vectoring system, which is active on all types of driving surfaces. In dynamic cornering, this software function brakes the two wheels on the inside of the curve slightly before they can begin to spin. These interventions are made even if the driver is not pressing the accelerator pedal at that time. The difference in propulsive forces causes the car to turn slightly into the curve – this self-steering response keeps the vehicle neutral longer, and its handling is therefore more precise, agile and stable.

The equipment, data and prices specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.