Press Release
Light and unshakable
As the top model, the A8 utilises the entire expertise that Audi has acquired in the body manufacturing sector. Since the debut of the previous generation in 1994, the brand with the four-ring badge has made consistent progress in the field of aluminium construction.
It all started with a revolutionary new approach – the Audi Space Frame ASF. This is a high-strength aluminium frame structure into which the large aluminium panels are integrated, thus assuming a supporting function. The space frame consists of a combination of aluminium extruded sections and castings that are positively connected to each other. Its central elements are the roof frame, side sills, seat cross members, roof posts and floor panels.
Innovative casting techniques and alloys are employed for the A8 model series. Large multifunctional castings, long continuous profiles and a high proportion of straight extruded sections reduce the number of components: a mere 29 castings account for 34 per cent of the structural weight. This significantly enhances comfort, since a low number of connections between components increases body rigidity. At the same time, the fact that there are fewer components has a positive effect on production processes and, consequently, on quality. The side panel, for example, consists of a single section which extends from the A-post to the rear end of the body.
Outstanding rigidity for dynamics and comfort
Apart from rivets, the connections are executed using various welding techniques i.e. MIG and laser welding and the laser-hybrid welding process. Laser welding allows large-area panels to be connected to the body structure particularly efficiently thanks to the fact that the resulting linear joins achieve superior strength and rigidity values to punctual ones. In all, around 20 metres of laser connecting seams will be found in the body of the Audi A8.
One of the two great strengths of the Audi Space Frame ASF is its outstanding rigidity. Its static torsional rigidity, a decisive factor for handling potential, is just as excellent as the so-called torsional eigen frequency which largely determines vibrational comfort. The ASF meets all current passive safety standards as well as plenty that have not yet come into force.
Low weight for low fuel consumption
Despite all these excellent qualities, the body structure weight of the Audi A8 is only about half as much as that of a conventional sheet-steel body. It amounts to around 215 kilograms – a figure that is customary for the mid-size class.
This weight-saving has two advantages: it improves handling characteristics and reduces fuel consumption. The new Audi A8 2.8 FSI is perfect proof of this: with a total weight of only 1690 kilograms its six-cylinder powerplant delivers superlative performance figures, while at the same time its fuel consumption of only 8.3 litres sets a new benchmark in the luxury class.
The high-strength structure of the A8 exhibits excellent safety characteristics. In a side-on collision, for example, the high-strength A-post braces itself against the other vehicle – this large casting is clear evidence of Audi’s superior expertise in the field of aluminium technology. In the interior, finely-tuned restraint systems work in conjunction with each other.
These include belt tensioners with belt force limiters and two-stage full-size airbags for driver and front passenger as well as side airbags integrated in the front and rear backrests and the sideguard large-area head airbag system for front and rear passengers.
Audi backguard active head restraints reduce the risk of whiplash. In the event of a rear-end collision the special shape of the seat restrains the upper body, the spring-loaded head restraints swing forward and support the head at an early stage. Belt tensioners, airbags and active head restraints are triggered by two impact sensors on the front, side and rear of the vehicle. Furthermore, in a crash of sufficient severity the hazard warning lights are activated and the engine switched off.
The lowest noise level in its class
Aerodynamics is a technical area in which Audi has played a leading role for many years. The drag coefficient of the A8 is only 0.27, for instance. Solutions such as underbody panelling facilitate high downforce on the axles for further enhanced directional stability. Intensive fine-tuning reduces turbulence, which also benefits aeroacoustics. Even at high speeds, the A8 is exceptionally quiet.
This is precisely where the fine-tuning of the new-generation Audi A8 delivers distinct improvements. The entire acoustics, for instance, have been revised and optimised with innovative materials – after all, noise insulation at Audi is always tackled from the point of view of intelligent light-weight construction. The result: without adding weight the Audi A8 exhibits the lowest rolling, road and ambient noise in its class – an important element for relaxed comfort in the saloon on long journeys.
The acoustics package also includes the underfloor panel for the body and engine encapsulation: this now has a three-layer structure. This new trilaminate consists of a cover fleece incorporating strategically placed absorption fleeces, a polypropylene film and a surface film. In addition, the wheel arches are fitted with a new lining: here too, new fibre fleece materials and textile surfaces ensure efficient sound insulation.
Optimised "acoustic" glass for the windscreen and side windows likewise offers improved insulation: here a special 0.8-millimetre-thick film made of polyvinyl butyral lies between two layers of safety glass, each of which is 2.1 millimetres thick.
Driving enjoyment in the luxury class
The character of the Audi A8 is a result of the synthesis of dynamic, light-footed driveability and exceptional ride and acoustic comfort. With its agility and steering precision the A8 has set new standards; in terms of handling it has the qualities of a sports car. Even long journeys provide enjoyment and relaxation at the same time.
To emphasise this unique character of the A8 even further, both strengths of the saloon have been enhanced. The rack-and-pinion steering with variable ratios and servotronic speed-dependent power assistance has been optimised and is more direct, similarly to the S8. Shock absorbers, bearings and air suspension settings have been updated. As a result, the new A8 responds more spontaneously to steering inputs, tackles winding country roads with precision and – as if on its own – maintains calm and supreme straight-line stability at high speeds.
Air suspension with an even more sensitive response
Similarly to the handling characteristics, ride comfort has also been improved: the standard adaptive air suspension is now more responsive to minor irregularities in the road surface. The continuously variable shock absorbers feature new seals to reduce friction, new valves optimise the characteristics, the entire hydraulics system has been retuned. The A8 even moves smoothly over transverse joints, with no vibration whatsoever. Together with the package designed to insulate the vehicle from rolling and road noise, the luxury saloon from Audi offers outstanding comfort.
The foundation for these excellent driving characteristics is provided by the Audi A8’s aluminium running gear, with five-link front suspension and self-tracking trapezoidal link rear suspension. The standard adaptive air suspension – featuring active continuously variable shock absorbers – solves the classic conflict between sporty handling and luxurious ride comfort. It offers four levels of ground clearance. On the motorway it lowers the body, thus improving stability and aerodynamic drag.
Suspension characteristics according to personal preferences
Furthermore, adaptive air suspension allows the driver to adjust the characteristics according to his/her own personal taste – with only one action in the "Car" menu of the MMI operating system. The following modes can be selected: automatic – with the emphasis on a balanced setup, dynamic – a particularly agile setting, comfort – with the focus on gentle cruising and finally lift for driving on very uneven terrain. In addition to the standard programme, adaptive air suspension sport is optionally available. It works with the same control modes as the standard suspension but has firmer characteristics overall.
All V6 and V8 models are fitted with 17-inch wheels; cast aluminium wheels with a 10-hole design are standard. The vast range of optional wheel designs and wheel sizes up to 20 inches has been further extended for the 2008 model year. In each case, high-performance disc brakes are located behind the wheels, held in place by aluminium floating callipers. A tyre pressure monitoring system is available on request; the electromechanical parking brake with starting assist and emergency braking function is standard.
Optionally available for the top Audi A8 W12 and Audi S8 models is the ceramic brake system. This combines utmost stability with a brake disc service life of up to 300,000 km.
