Audi RS4 Cabriolet (2008)

Audi has deployed the high-revving engine principle for the first time in the Audi RS4, which has a maximum engine speed of 8,250 rpm. The significant advantages of this principle are superior power output at high engine speeds and a smooth, eager responsiveness across the entire rev range. Further amplifying the high-performance experience is the high-revving V8 engine sound that enthusiast drivers live to hear.

For further enjoyment of the V8 sound system, pressing the "Sport" button on the dashboard produces a more aggressive engine exhaust note. Moreover, the electronic throttle control heightens its response to throttle inputs for a more sporty driving experience.

The ultra-compact V8

The V8 power unit is ultra-compact, fitting snugly into the engine compartment of the Audi RS4 without any body modifications. The camshaft and ancillaries, with the exception of the alternator, are all driven by a chain for easy maintenance.

Unique features of the V8 that powers the Audi RS4 versus the Audi S4 include modified pistons and con-rods, a new crankshaft together with its bearings, and new cylinder heads. A twin exhaust system with enlarged pipes provides even higher power output. These extensive measures enable the 4,163 cc engine to break through the magical 100 hp per liter barrier.

Drivetrain

Getting all this power on to the road obviously was a significant challenge, one that was solved by incorporating the quattro permanent all-wheel drive system. Over a quarter century's experience and market leadership in the all-wheel drive car segment represent genuine benefits for Audi's customers. The Audi RS4 features quattro all-wheel drive with asymmetric/dynamic torque distribution.

A center differential distributes the power to the front and rear wheels as required, thereby ensuring optimum traction. In variable road conditions, power can be diverted immediately in full to the front or rear, depending on the need. The distribution system, which under normal road conditions transmits 40 percent of the power to the front wheels and 60 percent to the rear, makes the Audi RS4 an even more impressively dynamic drive. Alongside traction, controllability, stability, load reversal and transitioning, aspects of agility and steering also have been substantially enhanced, underscoring the car's highly sporty character.

The center differential is a self-locking worm gear, which means that the locking action is prompted only under the influence of the drivetrain. When braking and cornering, however, the gearbox permits differences in engine speed. The rear axle differential is fitted with additional cooling fins.

The six-speed gearbox with very short gearshift travel combines compact dimensions with low weight and a high standard of shift comfort. Adapted to the power band of the Audi RS4, the gearing provides excellent power yield in practice, conveying the output of the engine to the car's driven wheels with maximum efficiency.

Suspension

Even the best drivetrain needs the proper chassis and suspension. A standard sports suspension ensures that the engine's output is transferred just as needed to the road. But Audi's new sports sedan boasts a high-performance aluminum suspension with a four-link front axle and a trapezoidal-link rear axle that ensures a superior ride. Precise steering, with sensitive feedback, sporty agility and excellent directional stability make the Audi RS4 the perfect car for the highway, country roads, and the race track.

Each wheel on the front axle is guided by four aluminum transverse links. The trapezoidal-link rear axle offers top-class driving dynamics. This torsion-proof and non-flexing trapezoidal link absorbs a large portion of the forces acting on the wheel. Together with the track link located further to the rear, this special configuration defines the elastokinematic behavior of the rear axle with ultimate precision.

Dynamic Ride Control

The Audi RS4 comes with Audi's Dynamic Ride Control (DRC), an entirely mechanical system that reduces both body roll and pitch along the car's longitudinal and lateral axes. This is accomplished by interconnecting the dampers diagonally by way of a central valve. Body movements during initial acceleration are largely eliminated in this way, as are pitching movements when braking or rolling movements when cornering rapidly. In the Audi RS4, quattro GmbH has succeeded in making the system more compact and lighter than in the Audi RS6.

The combination of quattro drive, DRC, and a suspension specifically tuned to the Audi RS4 allows this outstanding high-performance Audi to hold the road safely even in the absolute limit at top cornering speeds. The Audi RS4 features the latest generation electronic stability program designed and configured especially for this car. Its interventions now are later and shorter, and it also is possible to delay intervention further, or to disable the program altogether.

For the RS4, Audi designers produced a range of light and attractive cast aluminum wheels with a seven double-spoke design. A special manufacturing method yields wheels that are stronger, thinner and lighter.

Compared with the standard Audi A4, the Audi RS4 is lower by 1.2 inches (30 mm). Another important change is the wider track, increased by 1.5 inches at the front and 1.9 inches at the rear. The spring and damper tuning also have been adapted to the sporty dynamics of the Audi RS4.

Servotronic steering has been specially tuned to the requirements of the sports sedan. With its direct response and short travel, it is well suited to the overall character of the Audi RS4.

Brakes for the race track

The Audi RS4's impressive braking is based on a system that fits at least 18-inch wheels. The perforated and ventilated brake discs measure 14.4 inches in diameter at the front and 12.8 inches at the rear. They are designed in a floating arrangement, with the castiron friction ring of the brake system bolted onto the aluminum brake disc cover. The result is a significant improvement in brake resistance to fading, particularly under extreme loads. Another side effect of this technology is a reduction in unsprung mass.

Brake air flow is optimized by means of NACA ducts that keep the brake discs appropriately cool at all times. Featuring eight-piston fixed calipers originally developed for motorsports on the front wheels (four pistons and two brake pads on the inside and outside of each brake disc), as well as single-piston swing calipers on the rear wheels, the Audi RS4 offers supreme stopping power and directional stability.

Other features included in the electronic stability program are the electronic differential lock (EDL), traction control (ASR), electronic brake force distribution, and anti-lock brakes (ABS).

It also is possible to disable the stability program in two stages: in the first stage only the traction control (ASR) function is disabled; in the second stage the program is completely deactivated, including the traction control. As a result, there is no control intervention in any driving situation.

Design

The design of the Audi RS4 combines functionality with aesthetics. The car's appearance embodies the ultimate in uncompromising sportiness. In particular, the RS 4 demonstrates its enormous performance potential where such qualities really count, boasting features such as:

• Flared wheel arches, as a result of the 1.5-inch front and 1.9-inch rear track that is wider than the S4
• RS design bumpers with the trim grille in diamond look
• Flared side sills as well as door cut-out trim strips matched to the sills
• A rear spoiler integrated in the trunk lid and side panels
• A twin-chamber exhaust system with oval tailpipes
• Aerodynamically optimized twin-arm design RS exterior mirrors in aluminum appearance
• Standard 19-inch wheels of seven-double-spoke design
• RS4 badging at front and rear and on the side rubbing strips
• Grille and side window trim strips in matte aluminum appearance

The sporty look of the Audi RS4 is combined with an equally high level of functionality. The large inlets on the front end of the Audi RS4 guarantee optimum cooling of the V8 FSI engine. Flared wheel arches offer substantial space for standard 19-inch wheels. With enlarged tailpipe cross-sections, the twin-chamber exhaust system provides significantly reduced exhaust gas back pressure. The 1.2-inch lowering not only provides a sporty look but also is a major factor in delivering outstanding levels of driving dynamics.

Despite uncompromising sportiness, the car's close family relationship with the Audi A4 is unmistakable. The distinctive single-frame grille and the sweeping headlights, borrowed from the Nuvolari concept car, underscore the family heritage of the Audi RS4.

Interior

Premium quality typical of Audi and genuine sportiness typical of an RS model are combined in harmony in the interior of the Audi RS4. The Recaro sport bucket seats provide excellent lateral support. The RS bucket seats are covered in full silk nappa leather throughout.

Attention to detail is demonstrated in the choice of materials and the workmanship applied in processing them. Leather, aluminum and carbon fiber are the predominant materials in the interior. The RS steering wheel is covered in perforated leather. Carbon fiber trim inside the car serves to accentuate the sporting qualities of the Audi RS4, while milled aluminum door openers are echoed on the gear knob and the steering wheel. The gear knob, handbrake lever and steering wheel are covered in perforated leather.

The standard color LCD driver information system incorporated into the typical RSdesign cockpit features an oil temperature gauge as well as a stopwatch with lap timer function, a useful extra for those special track days so beloved by Audi RS4 drivers. The driver information system welcomes the driver with the exclusive RS welcome logo. The aluminum pedals are further evidence of the motorsports connection, and they also help to reduce weight.

The Audi RS4 Cabriolet has an acoustic roof that also insulates passengers from the cold. The use of fabrics with greater material density reduces the noise level inside the cabin, virtually matching that of the RS4 sedan, even at highway speeds. Thanks to its good thermal insulation and glass rear window, the Audi RS4 Cabriolet can be used without restriction in the winter.

Because of its limited production, the Audi RS4 Cabriolet will be offered with only standard equipment, including navigation system plus, preparation for mobile phone (Bluetooth®), SIRIUS® Satellite Radio, BOSE® sound system, heated front and rear seats, memory function for the driver seat and exterior mirrors, Bi-Xenon adaptive headlamps, rear parking system, acoustic convertible top, HomeLink® garage/gate opener, auto dimming exterior mirrors, auto dimming interior rear-view mirror with integrated compass, rain and light sensor with "coming home" feature, color driver information system, iPod® glovebox interface (no-cost option in place of standard 6-CD changer), brushed aluminum decorative inlays (no-cost option in place of RS4 carbon fiber decorative inlays).

An optional Premium package on the Audi RS4 consists of navigation system plus, Bluetooth, SIRIUS Satellite Radio, BOSE sound system, HomeLink garage/gate opener, auto dimming exterior mirrors, auto dimming interior rear-view mirror with integrated compass, rain and light sensor with "coming home" feature, and power rear and manual rear-side sunshades.

An iPod interface and aluminum interior inlays are no-cost options.

Safety

The Audi RS4 safety package is both comprehensive and highly sophisticated. Particular attention has been paid to the need for active driving safety. The quattro permanent allwheel drive system already offers more traction than conventional drive systems in critical driving situations. Its variable distribution of power across the two axles now also provides even greater benefit.

An additional boost to safety is provided by the electronic stability program, with its integrated dry braking function. When the road is wet, the system lightly applies the brake pads to the discs at regular intervals, unnoticed by the driver, to sweep water from them and so improve braking response.

The Audi RS4 features a tire pressure monitoring system as standard. The sensors located in the wheels continually measure the tire pressure at three-second intervals. In the event of an acute loss of pressure, the driver information system gives the driver both a visual warning sign and an acoustic alarm.

Passive safety of the highest standard

Great attention also was paid to the issue of passive safety. A rigid body, consistent and coordinated deformation properties, state-of-the-art restraint systems - including the two-stage front airbags - and the Sideguard head airbag system provide exemplary levels of occupant protection. This head-level side airbag system covers virtually the entire side window area, from the A-post to the C-post. The airbags themselves are inflated by a hybrid gas generator, which maintains the airbag pressure for several seconds to provide ongoing protection. This means Sideguard provides full protection even in a secondary collision such as when the car rolls over following initial impact. Audi RS4 Cabriolet models have side airbags that protect the head and thorax of front passengers.

The Audi RS4 Cabriolet's A-pillars are reinforced very effectively by means of highstrength tubes and their optimized structure - an indispensable source of extra safety if the car should roll over. Sills with an optimized thickness and cross-section boost the occupant cell's strength and occupant protection. High-strength tubes also are used in the seat, as a means of protecting occupants in the event of a lateral collision.

If the car should roll over, a roll-over protection system in the double rear bulkhead adds to occupant safety. In this case, two protective bars, controlled by sensors, are triggered behind the rear passengers within milliseconds. Together with the extremely rigid windshield frame, they help to preserve survival space for all occupants.