Distinct sports appeal, elegant style and supreme comfort – these are the characteristic features of the Audi A8. At the time of its market launch three years ago, this large sedan shot straight to the top of the luxury segment thanks to its dynamic qualities. The Ingolstadt brand is now unveiling a sporty top model of the very highest caliber: the Audi S8 stands for exceptional dynamism, as expressed by its engine, transmission, suspension and design, as well as for exclusiveness and luxury.
Its predecessor was already a sporty luxury saloon with an exceptionally individual character. The new Audi S8, launched in mid-2006, is set to continue this legacy and develop it further, with the objective of setting new standards in its class.
Sportiness is to be found in the genes of all Audi models. In the case of the S models, however, it is a declared principle, combined with comfort, aesthetics, elegance and uncompromising quality. The Audi S8, born from a fascination for technology, combines all these characteristics to produce a high degree of passion and superiority.
The Audi S8 is equipped with a new V10 engine that capitalises on the expertise of the Lamborghini Gallardo super sports car. This ten-cylinder engine delivers 450 bhp at 7,000 rpm and 540 Nm of torque – the latter available from just 3,500 rpm – from a capacity of 5.2 litres. As on the Le Mans winning R8, the most successful racing car in the world, FSI petrol direct injection assures superior power output in the Audi S8. This luxury saloon sprints from 0 to 100 km/h in 5.1 seconds, and is electronically governed at 155 mph.
The advantages are clear to see:
very spontaneous response, short reaction time
shorter shift points, quick gear changes
sporty, throaty sound when accelerating
beefy torque curve even at low engine speeds
sporty behaviour thanks to engine speeds up to 7,000 rpm
perfect synthesis of sporty driving pleasure and comfort on long journeys
The driveline and aluminium chassis of the S8 have been modified to suit the engine’s power. The latest generation of quattro permanent four-wheel drive with asymmetric/dynamic torque split transmits this power to all four wheels. The firmer settings of the adaptive air suspension - sport and a more direct steering ratio ensure that the power and dynamism of the drivetrain are put to the road with precision.
The design of the new S8 completes the picture – the sporty top model also has the looks of the most athletic luxury saloon car. There is an atmosphere of luxurious elegance inside the car. Its generous equipment including the headlight technology known as adaptive light and optional ceramic brakes advance the Audi S8 to the status of technology leader and ensure that it enjoys an exceptional position compared with the competition.
The driveline and aluminum chassis of the S8 have been modified to suit the engine’s power. The latest generation of quattro® permanent four-wheel drive with asymmetric/dynamic torque split transmits this power to all four wheels. The firmer settings of the sport-tuned adaptive air suspension and a more direct steering ratio ensure that the power and dynamism of the drivetrain are put to the road with precision.
As the sporty top model in the A8 line, the new S8 makes use of the entire expertise that Audi has acquired in the body manufacturing sector. Since the debut of the previous generation in 1994, the Ingolstadt brand has made consistent progress in the field of aluminium construction. It all stated 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 used for the current A8 series.
Multifunctional large castings, long continuous profiles and a high proportion of straight extruded sections reduce the number of parts used. Just 29 elements are used now instead of 50 castings, while the proportion of large castings has increased from 22 to 34 percent of structural weight compared with the predecessor. This progress improves comfort decisively because a lower number of connections between components makes it possible to increase 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.
The connections are formed by riveting as well as various welding techniques including MIG and laser welding and, for the first time, 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.
The body of the new Audi S8 includes a total of 20 metres of laser connecting seams. One of the two great strengths of the Audi Space Frame ASF is its outstanding rigidity. Its static torsional rigidity, a critical measure of dynamic potential, is around 60 percent higher than on the previous model. On the current A8, the natural frequency of torsion – the primary determining factor behind vibrational comfort – has increased by 38 percent.
The ASF meets all current passive safety standards as well as plenty that have not yet come into force. And thanks to its supreme engine power and highly rigid body, the S8 is permitted to tow a braked trailer weight of 2,300 kilograms. Despite all these excellent qualities, the body structure weight of the Audi S8 is only about half as much as that of a conventional sheet-steel body. It weighs in at 215 kilograms – a figure otherwise usually to be found in the upper midsize class. This weight-saving has two advantages: it improves handling characteristics and reduces fuel consumption.
The Audi S models have always epitomised high performance and refined sports appeal. The same applies to the S8 – it lends the design of the A8 a dynamic edge. This prestigious saloon is already inherently light and elegant in character – its aesthetic appeal reflects its exceptional position as a sports model in the luxury class. And because good design is always functional, the styling of Audi models always enhances drivability – there is extremely little lift at the rear axle, for example.
The S8 cuts a supremely athletic figure, but never looks aggressive. The most striking changes are to be found at its front end. The eye-catching single-frame grille bearing the S8 badge is in platinum grey, and its vertical struts have a chrome-look 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, four details hint at the potential of the V10 engine: emblems on the wings and the front brake callipers, door handles with aluminium trim strips and the aluminium-look exterior mirror housings. At the rear, the S8 badge, an integrated rear spoiler, a subtle light-refracting edge in the apron and an exhaust system with four oval 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.
In common with the exterior, the interior design of the Audi A8 reflects a character of dynamic elegance and high quality. This also applies to the lavish amount of space resulting from the saloon’s 2,944 mm wheelbase, to the smoothly flowing line of the cockpit and to the MMI (Multi Media Interface) control interface. With its clear ergonomics and intuitive, logical operating principle, this Audi system is still unequalled by the competition.
The S8 adds various specific accents to this luxurious interior. The standard specification includes sports seats with Valcona leather upholstery, with electrical adjustment and memory function, heating and lumbar support. The seat surfaces can be extended via a rail that slides forwards, without producing the usual gap in the cushion. The S8 sports seats, which have a wide range of adjustment features, have two-colour upholstery with stitching in a contrasting colour.
The four possible colour combinations – silver/black, paranut brown/black, silver/light grey and light grey/paranut brown – underscore the ambience of luxurious sportiness; the colours for the seat centre sections are different from those of the side sections and head restraints. The headlining is black together with a range of interior colour combinations, but the characteristic “S” interior colour silver is also available. Almost all interior colour combinations offered for the Audi A8 can be ordered. Further details of the interior distinguish the sporty top model from the A8.
The highly polished door sill trims are adorned with S8 logos, and the inlays are in brushed aluminium and carbon. The three-spoke leather multifunction sports steering wheel with the S logo features colour-contrasting stitching and aluminium-look shift paddles. Leather and aluminium-look trim are used for the selector lever knob; the parking brake and air vent surrounds also have an aluminium-look finish. The needles on the instrument dials are in white, their scales in light grey and their digits in the characteristic S italic script.
New V10 with FSI technology from the world of motor racing
For the first time in its history, the Audi brand is presenting a ten-cylinder engine for the S8 – the V10. A ten-cylinder engine is also synonymous with dynamic power in the Gallardo model built by the Italian super sports car brand Lamborghini, a subsidiary of Audi. The S8 also features FSI petrol direct injection. This combination of ten cylinders and FSI technology gives Audi a unique position on the market.
A ten-cylinder engine is the ideal power plant for realising sporting aspirations. It has the edge on a comparable twelve-cylinder unit thanks to the smaller number of components, resulting in lower moving masses and less internal friction; the fuel is consequently put to very efficient use. A V10 is moreover considerably lighter and more compact than a conventional 12-cylinder engine – including all its add-on components, the engine of the Audi S8 is just 685 millimetres long, 801 mm wide and 713 mm high. The bare engine measures 560 mm in length.
Although an eight-cylinder engine would be even more compact, to make it into the five-litre class it would need large, heavy pistons and connecting rods, so its ability to rev freely would be impaired as a result. It is no coincidence that many competitors have generally concentrated simply on high torque with their large-capacity V8 engines, rather than attempting to squeeze sporty performance out of them too. The 450 bhp V10 in the Audi S8 belongs to the next generation of Audi V-engines, all of which have a 90-degree included angle and a spacing of 90 millimetres between cylinder centres.
Its two banks of cylinders are offset by 18.5 mm. 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 84.5 mm. Its stroke is 92.8 mm, and its displacement 5,204 cc. The crankcase of the Audi ten-cylinder engine is produced by low-pressure die-casting, from a hypereutectic aluminium alloy. This technology renders separate cylinder liners superfluous; the liners are instead honed directly from the material by exposing the hard silicon crystals.
A so-called bedplate design – an intermediate frame – gives the crankcase extremely high torsional rigidity and improves its vibrational behaviour. The cast-in grey cast iron bearing bridges reduce the thermal expansion of the aluminium casing; they simultaneously keep the amount of play at the main crankshaft bearings within tight tolerances. The connecting rods are made from forged steel, and the pistons from an aluminium alloy. At the rated engine speed, each of them covers an average distance of 21.7 metres per second; oil-jet cooling prevents temperature peaks from occurring. With its crankpin offset of 18 degrees, the V10 fires at the ideal spacing of 72 degrees crankshaft angle.
A balancing shaft located within the “vee” eliminates the free inertial forces of the first degree and also contributes towards the engine’s notable refinement. All four camshafts of the ten-cylinder engine can be adjusted continuously by 42 degrees crankshaft angle via hydraulic camshaft adjusters, depending on the load and engine speed, to modify the valve opening overlap. They thus optimise filling of the combustion chambers and improve engine response.
The camshafts – complete with the balancing shaft, the oil and water pump and the auxiliaries – are driven by maintenance-free chains running on the reverse side of the engine. They actuate the 40 valves via roller cam followers with hydraulic valve-play compensation. The diameter of the valves on the intake side is 32.5 mm, and 28.0 mm on the exhaust valves. The exhaust valves are sodium-filled, for a cooling effect.
The V10 in the new Audi S8 uses the petrol direct injection principle known as FSI; this permits a high compression ratio of 12.5:1 and a correspondingly effective combustion process based on a homogeneous lambda value of 1. FSI technology has impressively demonstrated its dynamic potential in motor sport – the R8 racing car equipped with it participated in the Le Mans 24 Hours five times for Audi, emerging as winner on four of those occasions.
In the Audi S8, the FSI system is managed by a highly advanced Bosch Motronic bearing the designation MED 9.1, operating with ten individual pencil coils and two control units according to the master/slave principle. 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 variable intake manifold incorporates electronically controlled tumble flaps that induce a swirling movement in the air drawn in at low engine speeds and load, making the internal combustion process more efficient as a result.
The two-stage layout of the magnesium intake manifold serves the same purpose. Depending on load and engine speed, at around 4,000 rpm an electronically controlled valve switches from the long intake paths – measuring 675 mm – to the short paths 307 mm long. From that point on, the emphasis is on output rather than torque. The design of the single-pipe manifolds likewise contributes to the dynamically optimised charge cycle; it is matched precisely to the firing order of the V10.
On each cylinder bank, the manifolds for the first and second cylinder, and also for the fourth and fifth cylinder, are combined; they only converge with the manifold for the third cylinder relatively far down. Four close-coupled main catalytic converters take charge of exhaust emission control. The powerful ten-cylinder engine has been optimised for high torque as well as high engine power. It achieves 450 bhp at 7,000 rpm, and musters up 540 Nm of torque at between just 3,000 and 4,000 rpm.
More than 90 percent of the torque is available from as low as 2,300 rpm. The V10 exhibits spontaneous throttle response and very refined running, and under load it also produces a sonorous, musical acoustic backdrop, as befits a dynamic vehicle. It is a far cry from a rough-diamond sports engine: for all its sporty character, this ten-cylinder engine is very low-vibration and has plenty of refinement.
The V10 imparts the luxury saloon with the road performance of a high-calibre sports car. The Audi S8 races from 0 to 60 mph in 5.1 seconds. It effortlessly reaches its electronically governed top speed of 155 mph, thanks also to its low drag coefficient of Cd 0.29. The engine shows a distinctly modest thirst, needing only 13.4 litres of Super Plus fuel per 100 kilometres (provisional figure) – 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 1,940 kilograms, complete with the dynamic, sure-footed quattro drive. On the new Audi S8, every horsepower has to propel just 4.3 kilograms – giving it the power-to-weight ratio of a sports car.
Typically for an Audi, the new Audi S8 also relies on quattro permanent four-wheel drive and the superior traction that it offers in all conditions. 25 years of expertise acquired in this domain by the brand with the four-ring logo have led to the development of a new quattro generation with asymmetric/dynamic torque split – 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 end underlines the dynamic character of the Audi S8. If the road 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 should happen to spin, the electronic differential lock EDL controls it by applying the brakes.
As far as the driver is concerned, this newly compiled package of technologies means greater agility, a more spontaneous response to steering movements and even more stable handling. The new S8 is equipped with a six-speed tiptronic transmission as standard. In keeping with the character of this sporty top-of-the-line model, the final ratio of the automatic transmission is lower than on the A8 – the saloon is still capable of forceful acceleration even in sixth gear.
The electronic transmission control is optimised to change gear more dynamically. The driver can call up the transmission’s Sport mode at the selector lever. In this mode, upshifts are performed at even higher engine speeds, as high as 7,000 rpm which is both the V10’s nominal and maximum engine speed. It is in addition possible to change gear manually with the aluminium-look shift paddles located behind the steering wheel.
For Audi, lightweight design is a philosophy that has implications for every area of a vehicle. As in motorsport, the engineers developing the S8 fought to save every gram of weight possible. Thanks to its compact design and thinner walls, the V10 weighs just 220 kilograms – 20 kilograms less than a well-known competitor’s engine. Good axle load distribution and impressive road behaviour are the result. For the same reason, the battery and the power management are housed in the luggage compartment.
The basic version of the Audi A8’s air suspension, known as adaptive air suspension, already possesses distinctly sporty attributes thanks to its elaborate design. The axle links are made of aluminium. The front suspension consists of a four-link structure with two upper and two lower wishbones, and there is self-tracking trapezoidal-link suspension at the rear of the car. Various details of the setup have been revised on the S8.
The basis is adaptive air suspension - sport, the sports suspension 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 are 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 rack-and-pinion power steering with its variable ratio is roughly ten percent more direct in the straight-ahead position, 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 the same as with adaptive air suspension - sport, which is up to 20 mm lower depending on mode. On the S8, ground clearance is varied in three stages between 125 mm in the comfort mode and 95 mm at consistently high motorway speeds; this low level optimises the air flow and reduces fuel consumption as a result.
The Audi S8 is factory fitted with newly developed S-design cast aluminium wheels. Their dimension is 9 J x 20, the wide tyres are size 265/35. Tyres with run-flat characteristics based on the PAX system and 19-inch winter wheels are available as an option. An 18-inch brake system featuring four large-size ventilated discs assures a superlative braking performance. The brake callipers are painted black, and adorned with a titanium grey S8 badge at the front.
The optional ceramic brakes that were also recently made available for the twelve-cylinder A8 are a special feature of the S8. This makes Audi the only manufacturer worldwide to offer this technology in two production saloons. The impressive diameters of the ceramic brake discs – 380 mm at the front and 356 mm at the rear – are an immediate indication of their tremendous potential.
The discs, which are 38 mm thick at the front and 28 mm at the rear, are made from a composite material comprising high-strength carbon fibres embedded in hard, frictionally resistant silicon carbide, a material that has already proved its worth in the field of aviation and space travel. The discs are bolted to a stainless steel chamber via resilient connecting elements. The ceramic discs offer significant advantages compared with conventional steel discs.
They offer a high braking performance, especially at the limit, and are largely unsusceptible to heat fading – a major safety bonus for a sporty high-performance car such as the Audi S8. The high-tech material is completely resistant to corrosion. Ceramic discs will last for up to 300,000 kilometres, four times as long as steel discs. And not only that, at around five kilograms per unit, they weigh half as much as their steel counterparts – this reduction in unsprung masses improves both handling and ride comfort.
Optically, the high-tech brake system can be identified by the special cooling ducts and the perforation of the discs as well as by anthracite-coloured callipers with the “Audi ceramic” logo. A six-piston aluminium monobloc calliper is used at the front wheels, a nodular cast iron floating calliper at the rear. The dynamic stability system ESP is specially tuned for interaction with the ceramic brake system.
quattro drive is one of Audi’s core areas of expertise. It gives Audi drivers decisively more safety by assuring optimum traction in critical situations. 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.
The control strategy of the Bosch 5.7 is tailored specifically to the dynamics of the S8; it intervenes slightly later and more briefly. The system keeps the brake discs dry in wet conditions by lightly applying the pads to the discs at regular intervals – a process that goes unnoticed by the driver. In common with all Audi A8 models, the sporty top model comes complete with a package of restraint systems that are perfectly matched to its highly rigid aluminium body.
The package includes two front airbags that are activated in two stages, four side airbags integrated into the seat backs and 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 known as adaptive light, including LED daytime running lights, is standard equipment on every Audi S8.
In this case, the xenon plus headlights are equipped with static turning lights and dynamic cornering lights and coupled with separate LED daytime running lights. Located in a cloverleaf-shaped reflector and each consisting of five white light-emitting diodes, the daytime running lights on the Audi S8 consume a minimum, barely perceptible amount of energy.
Each diode has an output of just one watt – conventional dipped headlights have an output of up to 300 watts. This white colour of this light, which is similar to daylight, not only illuminates the road ahead, it also makes the driver’s own car immediately visible to all other road users. At the same time, it emphasises the striking design of the Audi front end.
Alongside its sporty, dynamic performance, the new Audi S8 has an additional strength to offer – an excellent price/performance ratio. Starting at a basic price of €97,600 in Germany, it comes with a wealth of standard features which set new standards, even in the sophisticated luxury segment. As well as adaptive light technology, 20-inch wheels and an 18-inch brake system, the standard specification incorporates other comfort and convenience equipment items.
These include sound-insulating double glazing for the windows, automatically dipping and electrically folding exterior mirrors, seat heating with six settings for all seats, a navigation system with high-performance DVD drive and a Bose surround audio system with CD changer. The door armrests and the centre console in the S8 are upholstered in leather, together with the seats.
The standard access and authorisation system known as advanced key permits the driver to open the S8 without having to take hold of the key. A transmitter in the key releases the central locking when the vehicle is approached. If the key is inside the car, the driver can start the ten-cylinder engine simply by pressing the start button. One particular highlight available to customers for the S8 is the Bang & Olufsen Advanced Sound System.
The fully digital system from the Danish high-end manufacturer redefines the standard yet again for demanding music lovers. This system incorporates 14 speakers, each energised by its own output stage. The output stages are grouped together in two amplifiers, which supply an output of more than 1,000 watts if required. The general rule is: the higher the output, the better the freedom from distortion in poor acoustic conditions – inside the car, there is already a basic background noise level of around 60 dB.
The dynamics of the frequency response is calculated such that the music has the perfect tone. When programming the digital sound processor and selecting and positioning the speakers, consideration was given not only to driving noise, but also to spatial conditions and the properties of materials in the S8 interior. The speakers are housed in enclosed capsules so that their vibration behaviour can be precisely controlled. Their anodised aluminium grilles underscore Audi’s expertise with this material.
The front tweeters use what is known as Acoustic Lens Technology: with their coated silk diaphragm domes, they act as perfect point sound sources. When the system is switched on, they extend out of the dashboard automatically. With all its qualities put together, the S8 – along with the rest of the A8 model line – is positioned as a luxurious and sporty saloon in the top car class. Its aluminium body based on the ASF principle, aluminium chassis, adaptive air suspension and quattro permanent four-wheel drive combine to produce its dynamic character.
A six-speed tiptronic transmission, three-spoke leather multifunction steering wheel and deluxe automatic air conditioning with moisture sensor and sun sensor provide maximum comfort and convenience. The luxury impression is also enhanced by the luggage compartment lid with power-assisted closing, the light and rain sensor and cruise control. The front seats can be adjusted electrically. Innovative technologies such as the Multi Media Interface MMI, battery power management, the electromechanical parking brake including auto release function and the light-emitting diodes in the rear lights underpin Audi’s proverbial “Vorsprung durch Technik”.
Sporty components and high-tech systems also play the leading role in the list of optional extras. The radar-controlled adaptive cruise control, for example, represents a major advance on conventional cruise control systems. This intelligent system permanently calculates the distance to the vehicle ahead and adjusts the car’s own speed accordingly by actively controlling the accelerator and brakes.
The interior lighting package with ambient lighting illuminates the interior in accordance with the situation at hand, and produces a new level of harmony with the interior design as a whole. The four-zone deluxe automatic air conditioning allows the individual precision adjustment of temperature and air distribution for all four seats. A hands-free car phone with cordless handset is available as an option to go with the Multi Media Interface MMI.
Bluetooth technology permits wireless communication with the in-car control unit. The speech control system for a great many infotainment functions enhances the operating system’s ergonomic convenience still further. With two additional modules, MMI is able to receive digital radio stations (Digital Audio Broadcasting, DAB) and digital TV stations. The personalisation system one-touch memory enables up to four drivers to use the S8 without them having to enter their preferred settings all over again each time.
The system identifies the driver by his or her fingerprint, which is scanned by a sensor on the advanced key start button, and compares it with the memorised prints. Once the driver has been successfully identified, an array of processes are activated: the seats, mirrors and steering column are adjusted in accordance with the pre-selected configuration, as are the air conditioning’s temperature and air distribution, and a series of infotainment settings.
Aluminum ten cylinder V90 degrees spark-ignition FSI gasoline direct injection, magnesium two stage variable intake manifold with integrated charge movement flaps, regulated high pressure and low pressure fuel system
Front mounted, longitudinal
3.33 in.; 84.5 mm
3.65 in.; 92.8 mm
12.5 : 1
6-speed Tiptronic transmission with DSP and additional sport program
Permanent four-wheel drive with self-locking center differential with asymmetric/dynamic torque and electronic stabilization program ESP