Over seven million models with quattro® technology have been built to date, making Audi the world’s most successful manufacturer of premium cars with permanent all-wheel drive. From compact cars to saloons to supercars, quattro is synonymous with legendary traction, sure handling and a unique and exclusive brand of driving pleasure.
It doesn’t matter how mighty the engine is: its power first has to be channelled via the wheels before reaching the road. The quattro permanent all-wheel-drive system splits drive power between the front and rear wheels to optimum effect. This enables an Audi fitted with quattro to keep making safe progress with ease in situations where two-wheel-drive vehicles no longer have any forward traction, such as on slippery surfaces or loose terrain.
Throughout its 30 years of existence, Audi has never ceased to explore new territory with quattro permanent all-wheel drive, whether it has been for compact models with transverse engines or for the Audi R8 high-performance sports car. This has resulted in a long range of innovations right up to today, spanning from the classic manually locking centre differential on the original “Ur-quattro” to the latest version to evolve in the form of the crown-gear centre differential fitted in certain Audi RS models from quattro GmbH.
The quattro drive system employed in most Audi models is based on a self-locking centre differential. The principle is as simple as it is ingenious: if the wheels on one axle lose grip and threaten to spin, it automatically redirects the drive power to the other axle. With a basic distribution of 40:60, 40 percent of the power reaches the road via the front wheels and 60 percent via the rear. To counter any wheel slip that occurs, the system can direct up to 70 percent of the drive power to the front or up to 85 percent to the rear. The benefits of this are more grip when accelerating and greater safety thanks to the exceptional roadholding.
The optional quattro sport differential intensifies the inimitable quattro sensation by countering the general tendency of vehicles to understeer when turning into and moving through corners. The addition of superposed two-stage gearing units ensures that the wheels on the rear axle receive different levels of drive torque. The redistribution of drive forces virtually pushes the car into the corner. The reduction in load at the front axle is less, allowing it to transfer more lateral force at the tyres. As a result, the vehicle follows the turning angle of the front wheels as if it were on rails.
The brand with the four rings devised a completely new quattro drive system for compact models with transverse engines, such as the Audi TT and Audi A3. An electronically controlled and hydraulically operated multi-plate clutch directs the vast majority of the engine’s power to the front wheels in the basic configuration. A control unit draws on a multitude of data readings to constantly analyse the prevailing driving conditions. If necessary, it can divert an infinitely adjustable proportion of the drive torque to the rear axle – depending on the handling characteristics, driving situation and current Audi drive select mode. In extreme cases, nearly all of the drive power flows to the rear wheels.
The latest generation of quattro permanent all-wheel drive is showcased by the Audi RS models from the A4 and A5 ranges. The new centrepiece – a self-locking crown-gear centre differential – brings about a further increase in traction, helped by sets of plates with high locking values. The centre differential’s more compact design furthermore has a beneficial effect on weight. The asymmetric basic power split of 40:60 is retained to the benefit of handling dynamics. However, a higher percentage of the drive torque can now be directed to the front or rear wheels when required.
More equal cornering forces for greater safety: in conjunction with torque vectoring, quattro also distributes the drive forces individually to each wheel to suit the driving situation. By applying carefully measured amounts of braking force at both wheels on the inside of the bend, the torque distribution takes effect before any wheel slip actually occurs. The resultant yawing moment helps with cornering and allows for sporty handling characteristics that can be controlled with great precision along with even more agility and traction.