Audi Drops V10 into Flagship Limousine

Motoring Channel Staff - 21/10/2005

At the time of its market launch three years ago, the A8 large saloon shot straight to the top of the luxury segment thanks to its dynamic qualities.

And now the brand with the four-ring emblem is unveiling a sporty top model of the highest calibre in the luxury segment: the new Audi S8. It will be appearing on the market in the middle of 2006.

Engine: In outfitting the S8 with the V10, Audi is introducing an engine technology that has long been demonstrating its performance potential in the world of Formula 1 racing. The Italian super sports car brand Lamborghini, a subsidiary of Audi, likewise regards the 10-cylinder engine as synonymous with dynamic power.

According to Audi, this engine concept has a much more sporty emphasis than a comparable 12-cylinder power unit. It insists that 10-cylinder engines are more compact and lighter; thanks to the smaller number of components, they have lower moving masses and less internal friction.

The 331kW (450hp) V10 is the second generation of Audi V-engines, all with a 90° included angle and a spacing of 90 millimetres between cylinder centres. Key areas of the Audi version have been reengineered compared with the engine in the Lamborghini Gallardo. The bore has been increased from 82.5 to 84.5mm; the stroke is 92.8mm and the displacement 5204cc.

A so-called bedplate structure – an intermediate frame – reinforces the extremely compact crankcase, which is made from cast aluminium.

With its crankpin offset of 18°, the V10 fires at the ideal spacing of 72° crankshaft angle. A balancing shaft located within the "vee" eliminates the so-called free inertial forces of the first degree and also contributes towards the engine's notable refinement.

All four camshafts can be adjusted continuously by 42 degrees crankshaft angle, depending on load and engine speed, to optimise filling of the combustion chambers and thus enhance the power output. They are driven by no-maintenance chains and actuate the 40-valves via roller cam followers.

The V10 in the new Audi S8 uses FSI petrol direct injection and this permits a high compression ratio of 12.5:1 and a correspondingly more effective combustion process based on a lambda value of 1. The common rail injection system delivers the fuel directly to the combustion chambers in precisely metered amounts, at a pressure of up to 100 bar.

The two-stage magnesium variable intake manifold incorporates electronically controlled tumble flaps that induce a swirling movement in the air drawn in. Four close-coupled main catalytic converters take charge of exhaust emission control for the V10 of the Audi S8.

The powerful 10-cylinder engine is designed for impressive torque as well as engine power. It generates 331kW @ 7000rpm, but musters up 540Nm of torque @ just 3500rpm.

Ninety percent of the torque is available from as low as 2300rpm, and the V10 exhibits spontaneous throttle response and very refined running, and under load it also produces sonorous acoustics, as befits a dynamic car.

The V10 imparts the luxury saloon with the road performance of a high-calibre sports car, as the Audi S8 races from 0 to 100km/h in 5.1 seconds. The speed is not governed electronically until the needle reaches 250km/h.

The engine shows a distinctly modest thirst, needing only 13.9 litres of fuel per 100 kilometres – a figure achieved partly thanks to the consistent use of lightweight design, which clearly sets the A8 range apart from its competitors.

With its innovative aluminium body, the Audi Space Frame (ASF), the S8 weighs just 1940 kilograms, including the dynamic, sure-footed quattro drive. On the new Audi S8, every horsepower has to propel just 4.31 kilograms – the power-to-weight ratio of a sports car.

Drivetrain: Typically for an Audi, the new S8 likewise focuses on quattro permanent four-wheel drive. As a result it produces superior traction in all surface conditions. 25 years of expertise acquired in this domain by the brand with the four-ring emblem have led to the development of a new quattro generation with asymmetric/dynamic torque distribution – further evidence of Audi's philosophy of "Vorsprung durch Technik".

A centre differential, installed longitudinally in the driveline, distributes power between the front and rear wheels according to the prevailing situation. Normally, 40 percent is routed to the front wheels and 60 percent to the rear, this slight emphasis on the rear underlining the dynamic character of the Audi S8. If the surface conditions change, the purely mechanical differential responds without any delay; it can divert up to 85 percent of power to the rear wheels, and as much as 65 percent to the front wheels. If a wheel on one axle spins, it moreover overrides the Electronic Differential Lock (EDL) by applying the brakes.

The new S8 is equipped with 6-speed tiptronic as standard. In keeping with the character of this saloon model, the final ratio of the automatic transmission is lower than on the A8 – the saloon is still capable of forceful acceleration even in 6th gear. The electronic transmission control is optimised to change gear more dynamically, plus the driver can call up the transmission's Sport mode via the selector lever – it still performs upshifts even at relatively high engine speeds. It is in addition possible to change gear manually with the shift paddles located behind the steering wheel.

For Audi, lightweight design is a philosophy that has implications for every area of a vehicle. The V10 in the Audi S8 weighs in at a mere 220 kilograms, in other words 20kg less than an equivalent competitor engine. Good axle load distribution and impressive road behaviour are the result. For the same reason, the batteries and the energy management are housed in the luggage compartment.

Chassis: The basic version of the Audi A8, adaptive air suspension, already possesses distinctly sporty attributes thanks to its elaborate layout. The control arms are made from aluminium; the front suspension consists of a four-link structure, and there is self-tracking trapezoidal-link rear suspension. Various details of this layout were revised on the S8.

The basis is "adaptive air suspension sport", the sports suspension layout that is available for the A8 as an option. On the S8, the characteristics of the air springs and the shock absorbers integrated into the air-spring bellows have been made somewhat firmer. With a further reduction in rolling and pitching movements, the sporty top model behaves with even greater agility and manoeuvrability, but is as stable and safe as ever. The elastokinematics of the rubber mounts in the axles have likewise been modified in keeping with the character of the S8. The variable steering ratio is roughly ten percent more direct, for even more spontaneous handling.

Drawing information from seven special sensors and a number of other parameters, the damping responds adaptively to the prevailing requirements in a fraction of a second. Its control system features four driving modes – automatic, comfort, dynamic and lift – which the driver can call up via the terminal of the MMI operating system.

The body's ride height is as envisaged in conjunction with adaptive air suspension sport, which is already 20mm lower than standard. On the S8, ground clearance is varied in three stages between 125mm in the comfort mode and 95mm at constant high motorway speeds.

The Audi S8 is equipped ex works with S-design cast alloy wheels. Their dimension is 9J x 20, and the wide tyres are size 265/35. An 18-inch brake system assures a superlative braking performance. It features four large-size ventilated brake discs. The brake calipers are painted black, and adorned with a titanium grey S8 badge at the front. The discs on the front wheels measure 385 millimetres in diameter, and 335mm at the rear.

The optional ceramic brakes that also became available for the twelve-cylinder A8 in summer 2005 are a further special feature of the S8. They are made from a composite material comprising high-strength carbon fibres embedded in hard, frictionally resistant silicon carbide.

The ceramic discs offer significant advantages compared with conventional steel discs. They are about half the weight, are largely insusceptible to heat fading and corrosion, and achieve an operating distance of up to 300,000 kilometres – four times that of steel discs. Optically, the high-tech brake system can be identified by the special perforation on the large-size discs and the anthracite-coloured calipers with the "Audi ceramic" lettering.

Design: The models in Audi's S range have always epitomised refined sports appeal. The same applies to the S8 – it lends the design of the A8 a dynamic edge. This representative saloon is already inherently light and elegant in character – its aesthetic appeal reflects its exceptional position as a sports model in the luxury class.

The most striking differences are to be found at its front end. The eye-catching single-frame grille displaying the S8 emblem is in platinum grey, and its vertical struts have a chrome finish. Beneath the grille, there are three low air inlets cut into the front apron. The two large air inlets beneath the headlights are filled with honeycomb grilles.

Down the sides, in addition to the 20-inch wheels and the special brakes, three details hint at the potential of the V10 engine: emblems on the wheel arches, door handles with aluminium strips and the aluminium-look exterior mirror housings.

At the rear, the S8 emblem, a spoiler integrated into the luggage compartment lid, a subtle light edge in the apron and an exhaust system with four ellipsoidal tailpipes complete the range of optical modifications. The S8 is the only model in the A8 range to be available in the exclusive colour Daytona Grey, pearl effect.

Interior: In common with the exterior, the interior design of the Audi A8 reflects a character of dynamic elegance and high quality – from the supple flow of the driving area to the MMI user interface (Multi Media Interface), which remains unequalled by any competitor thanks to its logical, intuitive operating principle.

The S8 adds various specific accents to this luxurious interior. This is the first time that bi-colour seats with seams in a contrasting colour have been used as standard; their four colour combinations emphasise the air of luxurious sports appeal. The colours for the seat centre sections differ from those for the side sections and head restraints. The headlining is additionally available in the S models' signature colour silver.

Further details of the interior distinguish the sporty top model from the A8. The door sill trims are adorned with S8 emblems, and the inlays are in brushed aluminium or alternatively carbon fibre. The three-spoke leather multifunction sports steering wheel with the S emblem features colour-contrasting seams and aluminium-look shift paddles. Leather and aluminium are used on the selector lever knob. The needles on the instrument dials are in white, their scales in light grey and their values in the characteristic S italic script.

Safety: quattro drive is one of the core areas of expertise of the brand with the four-ring emblem. It gives Audi drivers decisively more safety by always assuring optimum traction. The asymmetric/dynamic torque split that is possible on the new Audi S8 builds on this already significant advantage. The high-performance brake system, too, makes a substantial contribution towards active safety. The S8 is equipped with a dynamic stability system that can be deactivated if required. Its control strategy is tailored specifically to the dynamics of the S8.

In common with all other Audi A8 models, the S8 sporty top model comes complete with a package of restraint systems that are perfectly matched to the highly rigid aluminium body. The package includes two front airbags, four side airbags and large-area sideguard head airbags. All five three-point belts in the Audi S8 are fitted with belt tensioners. Active head restraints for the front seats reduce the risk of whiplash injuries in the event of a rear-end collision.

The innovative lighting technology adaptive light with LED daytime running lights is standard equipment on every Audi S8. Here, the xenon plus headlights are equipped with static turning lights and dynamic cornering lights. The separate LED daytime running lights, each of which consists of five white light-emitting diodes and consumes only a minimal amount of energy, can be considered a pioneering invention.

Equipment: The Audi A8 is already a luxuriously equipped saloon. It features for instance deluxe automatic air conditioning, the MMI operating system, the Driver Information System, the electromechanical parking brake complete with starting assist function, air suspension, the exclusive audio system and the electrically adjustable front seats.

The Audi S8 extends this package with a whole array of other standard features. In addition to adaptive light technology, the special 20-inch wheels and the 18 inch brake system, it incorporates further luxury features in the version for the German market: advanced key, the keyless access and authorisation system including starter button for the V10, sound-insulating double glazing for the windows, heated front and rear seats, a navigation system with DVD drive and a surround audio system with CD changer. The door armrest and the centre console in the S8 are upholstered in leather, together with the seats. The sports seats are equipped with lumbar supports and a memory function.

One particular highlight that is available as an option is the Advanced Sound System from Bang & Olufsen. The fully digital system from the Danish high-end manufacturer integrates 14 speakers, each energised by its own output stage. The output stages are grouped together in two amplifiers, which supply an output of 1100 Watts if required. The front tweeters use what is known as Acoustic Lens Technology, and act as perfect punctiform sound sources. This sound system represents the state of the art in audio reproduction adding special allure to the deluxe equipment of the Audi S8.