New generation of quattro drive
Getting all this power on to the road was of course a significant challenge. And to successfully meet this challenge, Audi - naturally - focuses on quattro permanent four-wheel drive, where 25 years of experience and superior market leadership in the four-wheel-drive passenger car segment give the customer significant benefits. Now, the RS 4 features a new generation of quattro drive with asymmetric/dynamic distribution of engine power and torque.
The Torsen power divider delivers the output and torque of the engine individually to the front and rear axle as required, thus ensuring optimum traction at all times: reflecting even minor changes in road conditions, the flow of power is re-directed immediately as a function of torque, with up to 100 per cent of engine power and torque going to just one axle whenever appropriate. This new distribution of drive power makes the Audi RS 4 an even more dynamic performer on the road. Apart from traction, ease of control, stability, load change and transient behaviour, the car's agility and steering behaviour in particular have been significantly improved once again, clearly underlining the very sporty performance and character of the RS 4.
The term "Torsen" comes from "torque" and "sense", which, taken together, quite literally means "sensing the development and build-up of torque". The Torsen differential is a self-locking worm gear system building up its locking action only under power, while allowing differences in speed both when applying the brakes and in bends.
Ensuring very short gearshift travel, the six-speed gearbox combines compact dimensions with low weight and a high standard of shift comfort. Adapted to the power unit of the RS 4, the individual gear increments provide excellent power yield in practice, conveying the output of the engine to the drive wheels of the car with maximum efficiency.
Chassis and Suspension
Superior at all times
Even the best drivetrain is nothing without the right chassis and suspension. Which is precisely why quattro GmbH consistently uses the benefits of quattro drive and a supreme engine on the Audi RS 4: The sports suspension featured as standard serves to reliably convey the superior power of the engine on to the road appropriately at all times.
This superiority is ensured on Audi's new sports saloon by high-performance aluminium suspension with a four-arm front axle and trapezoid-arm rear axle. Precise steering behaviour, sensitive feedback from the steering, sporting agility, and excellent directional stability make the RS 4 the perfect car both for the race track and for the motorway and country road.
Each wheel on the front axle runs on four aluminium track control arms. The trapezoid-arm rear axle, in turn, offers an equally outstanding, first-class potential in driving dynamics, the torsionally and flexurally stiff trapezoid arm taking up most of the forces acting on the wheels. Together with the track arm further to the rear, this special configuration defines the elastokinematic behaviour of the rear axle with ultimate precision.
Dynamic Ride Control
The Audi RS 4 comes with Audi's DRC Dynamic Ride Control featured for the first time in the Audi RS 6. DRC serves to reduce both body roll and dive along the car's longitudinally and lateral axes.
This dynamic body control is ensured by the specific flow of oil between the damp¬ers in diagonal arrangement, largely eliminating any movement of the body when setting off (squat effect) and preventing both body dive when applying the brakes and body roll in fast bends. The result, clearly, is an even higher standard of driving dynamics in the RS 4.
DRC has already won over many enthusiasts in the RS 6. And now, introducing the system in the RS 4, quattro GmbH has succeeded in making DRC Dynamic Ride Control even more compact and lighter, the system now not even requiring an electronic control unit. Instead, the individual suspension dampers are connected hydraulically to one another by a central valve, adjusting instantaneously to every driving situation on the road.
The combination of quattro drive, DRC, and the suspension specifically geared to the RS 4 allows this outstanding high-performance Audi to quite literally "run on rails" even at the highest speeds in bends, thus maintaining its superior performance when other drive concepts have long reached their limits. And it almost goes without saying that the Audi RS 4 features the latest generation of ESP stability control designed and configured especially for this car.
18-inch wheels featured as standard
The new Audi RS 4 comes as standard on 18-inch wheels boasting 255/40 tyres. 19-inch wheels are available as an option. Focusing carefully on the RS 4, Audi's designers have created both light and at¬tractive cast aluminium wheels in five-arm design, a special production process ensuring enhanced stiffness and lower weight on even thinner walls. The 19-inch wheels come on 255/35 19 tyres, and are also available as an option with special Pirelli P Zero Corsa sports tyres made specifically for racing but also suitable for road use. Compared with the "normal" A4, the RS 4 is lowered throughout by 30 millimetres. A further important change is the wider track, up by 37 millimetres at the front and 47 millimetres at the rear. Both the springs and dampers have of course also been adapted to the superior potential of the RS 4 in their dimensions.
The servotronic power steering has likewise been modified to meet the particular requirements of Audi's new sports saloon, responding directly to the driver's commands and ensuring short, crisp steering travel most appropriate for the RS 4.
Brakes for the race track
The RS 4 also offers truly outstanding deceleration and stopping power ensured by the 18-inch brake system. Cross-drilled and inner-vented, the brake discs measure 365 millimetres in diameter up front and 324 millimetres or 12.8" in diameter at the rear. They come in floating arrangement, meaning that the cast-iron friction ring on the brake system is bolted on to the aluminium brake disc cover. The result is a significant improvement of the brakes' resistance to fading, particularly under extreme loads, that is at high operating temperatures. This serves to prevent the so-called "bulging" effect, with the brake discs bulging out and the brake pads no longer coming to rest perfectly on the discs. A further positive side-effect of this technology is the reduction of unsprung masses in the interest of enhanced driving dynamics, which almost completely eliminates any distortion or adverse tension in the materials used.
A further advantage is the optimisation of brake venting geometry by means of Naca jets keeping the brake discs appropriately cool at all times.
Featuring custom-made RS eight-piston fixed callipers on the front wheels (four pis¬tons and two brake pads on the inside and outside of each brake disc) as well as single-piston swing callipers on the rear wheels, the Audi RS 4 offers supreme stop¬ping power and directional stability. The ESP 8.0 stabilisation program, electronic brake-force distribution EBD, and the ABS anti-lock brakes have all been tailored to the specific dimensions of the brake system.
An additional safety feature offered by ESP is the dry braking function: In bad and wet weather the system regularly applies the brake pads to the discs in a pro¬cess virtually unnoticeable to the driver, thus removing water from the brake discs in the interest of enhanced stopping power. Further features included in the ESP stability program are the electronic differential lock, anti-spin control, and the ABS anti-lock brakes.