Ceramic brakes for the 12-cylinder Audi A8

Audi is presenting a new braking technology destined for its series production debut. The brand's flagship model, the 12-cylinder A8, will in future be available with ceramic brakes as an option. As well as quadrupling brake service life compared to conventional steel discs, the new brakes also offer outstanding braking power, even when the car is being driven to its limit, as well as supreme resistance to fading. The far lower weight also heralds benefits in terms of ride comfort and handling characteristics by reducing the unsprung masses.

The brake discs are made from reinforced ceramic, a material which has already proven itself many times over in the field of aeronautical and aerospace engineering. The ceramic material's composite structure is made up firstly of silicon carbide, an extremely hard and abrasion-resistant base material with a crystal structure similar to that of diamond. The high-strength carbon fibres which are then embedded in this base material are able to absorb the stresses that occur in it.

The high-tech material offers a whole spectrum of benefits. The most visually apparent of these is its insusceptibility to corrosion; no signs of rust formation will be found on a ceramic brake disc. The sporty looks, featuring distinctive perforation patterns and red brake callipers, also add eye-catching styling touches.

The technical benefits have an even greater impact: first, there is the weight-saving of some five kilograms, or around 50 percent, per wheel. The result is a clear reduction in the unsprung masses at the wheels, which in turn makes the ride even more comfortable. The vehicle's handling characteristics are also enhanced by the brake unit's lower weight.

The high abrasion resistance of the ceramic discs means a service life of up to 300,000 kilometres under standard day-to-day operating conditions, four times greater than that expected of a steel disc. Plus, the degree of wear over the brake's service life is a mere 0.5 millimetres.

The ceramic braking system also represents a significant step forwards in terms of brake performance. The discs are able to offer tremendous braking power, even when the vehicle is being driven to its handling limits. Resistance to fading, which refers to the marked loss of braking power following repeated application of the brakes as can occur on long mountain descents, is far superior than with conventional brakes. For high-performance vehicles such as the W12-powered A8 this translates into far greater safety reserves out on the road.

Motorists are also able to appreciate the virtues of the ceramic brake on a more subjective level, thanks to the clearly defined pedal feel under all operating conditions. Neither is there any risk of the state-of-the-art brake discs being afflicted by brake judder, irrespective of the operating conditions.

Ceramic discs with a diameter of 380 millimetres are fitted at the front to partner 19-inch wheels. The discs at the rear measure 356 millimetres across. The ceramic brake disc ring is bolted by means of ten flexible connector elements to a stainless-steel bowl which in turn links it to the wheel hub. The elaborate cooling duct geometry used for the internally ventilated brake disc ensures optimum brake disc cooling. 6-piston monoblock aluminium callipers from Brembo at the front brakes and sliding-calliper brakes at the rear guarantee a vice-like grip on the discs. Electromechanical operation of the parking brake continues to make up part of standard specification as it does on all the other A8 models.

The new ceramic brake will be available to order as an option for the A8 W12 and A8 L W12 quattro 12-cylinder models from July2005.

MUNICH, Germany -- Audi AG will offer carbon ceramic brakes on the A8 sedan starting this month. That makes Audi the fourth automaker after Porsche AG, Ferrari and Mercedes to offer the high-performance option.

Ceramic braking discs are much lighter than regular brakes - about 11 pounds a wheel in the Audi A8, compared with 22 pounds for regular metal discs. They do not rust and typically last about four times as long as conventional steel brakes. Audi claims they can last about 186,000 miles under standard braking conditions.

The technology was inspired by the carbon brakes used in Formula One racing. Composite ceramic brakes debuted on a production car in 2001 when Porsche offered them as an option on the 911 car. Since 2004 the option also is available on the Boxster. Porsche charges $9,443 for the technology, which is standard on the $545,944 Carrera GT supercar.

SGL Carbon of Wiesbaden, Germany, supplies the brakes to Audi and Porsche.

Italy's Brembo S.p.A. supplies ceramic brakes to Ferrari and Mercedes.

Ferrari introduced ceramic brakes as standard equipment on the 2002 Enzo limited edition. The technology is a $16,643 option on the F430 and is part of the $28,220 handling package available for the 575M Maranello and 612 Scaglietti.

Durability issue

Brembo pioneered the technology in 1980 for the Formula One racetrack. It took more than 20 years to get the brakes into production models because durability and responsiveness at low temperatures had to be improved.

The result is a better brake feel, no fade even under extremely adverse conditions, and a real-life stopping distance reduced by as much as 5 feet when going from 62 mph to zero because of the ceramic brake's quicker response.

Audi has not set pricing, but a company spokesman said it aims to undercut Porsche's prices significantly.

The brakes will be available as an option worldwide on the top-of-the-line A8 with the 450-hp, 12-cylinder gasoline engine. Audi sold 1,850 units globally last year. An Audi source said the company is expecting an initial take rate of about 20 percent, or close to 400 units annually.

Audi expects that the percentage of its models with ceramic brakes will rise sharply as soon as it brings the technology into volume production. The cost of the ceramic discs, which is now about 30 times as high as steel discs, then could drop to a cost three to four times as high.

Possible models

Likely candidates for the technology would be Audi's high-performance RS models, the upcoming mid-engine sports car based on the Le Mans concept, as well as lower-powered A8 models. While the current ceramic brake is designed for 19-inch wheels, Audi is developing a version for 18-inch wheels.

The technology will help Audi gain an edge over its chief competitors. BMW doesn't offer the brakes, and Mercedes uses them only on the limited-edition, 626-hp SLR McLaren.

BMW spokesman Thomas Gubitz said the company has reservations about the performance of ceramic brakes at low temperatures. He also cited the good performance of BMW's current conventional brakes.

"It's very easy. If it's possible to reach the same performance numbers with a normal brake, it makes no sense to use ceramics."

Distinct sports appeal and supreme comfort – these are the two defining characteristics of the Audi A8. At the time of its market launch three years ago, this large saloon shot straight to the top of the luxury segment thanks to its dynamic qualities. The brand with the four-ring emblem is now unveiling a sporty top model of the very highest calibre in the luxury segment: the new Audi S8.

It will be appearing on the market in the mid of 2006, with a price tag of EUR 97,600.

The Audi S8 is equipped with a new V10 engine that capitalises on the expertise of the super sports car Lamborghini Gallardo. The 10-cylinder power unit develops 450 bhp of power and 540 Nm of torque from a swept volume of 5.2 litres. The torque value is achieved at as low an engine speed as 3,500 rpm. 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 250 km/h.

Distinct sports appeal and supreme comfort – these are the two defining characteristics of the Audi A8. At the time of its market launch three years ago, this large saloon shot straight to the top of the luxury segment thanks to its dynamic qualities. The brand with the four-ring emblem is now unveiling a sporty top model of the very highest calibre in the luxury segment: the new Audi S8.
It will be appearing on the market in the mid of 2006, with a price tag of EUR 97,600.

The Audi S8 is equipped with a new V10 engine that capitalises on the expertise of the super sports car Lamborghini Gallardo. The 10-cylinder power unit develops 450 bhp of power and 540 Nm of torque from a swept volume of 5.2 litres. The torque value is achieved at as low an engine speed as 3,500 rpm. 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 250 km/h.



The driveline and chassis of the S8 have been modified to reflect the engine's power. A quattro drivetrain of the latest generation with asymmetric/dynamic torque distribution diverts the engine's power to all four wheels. The firmer settings of the adaptive air suspension sport and modifications to the steering ensure that the power and dynamism of the drivetrain are translated with precision into locomotion.

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 lavish equipment lends the Audi S8 a pre-eminent status within the competitive field.



Engine

New V10 with FSI technology adopted from the world of motor racing

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 ten-cylinder engine as synonymous with dynamic power. This engine concept has a much more sporty emphasis than a comparable twelve-cylinder power unit. Ten-cylinder engines are more compact and lighter; thanks to the smaller number of components, they have lower moving masses and less internal friction.

The 450 bhp V10 is the second generation of Audi V-engines, all with a 90-degree 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 84.5 mm; the stroke is 92.8 mm and the displacement 5204 cm3. 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 degrees, the V10 fires at the ideal spacing of 72 degrees 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. 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. FSI technology has impressively demonstrated its potential in motor sport – the R8 racing car equipped with it participated in the Le Mans 24 Hours on five occasions for Audi, winning the race on four of those occasions.



The powerful ten-cylinder engine is designed for impressive torque as well as engine power. It generates 450 bhp at 7,000 rpm, but musters up 540 Nm of torque at just 3,500 rpm. 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 sonorous acoustics, as befits a dynamic car.

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

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Drivetrain

Even more dynamism

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 six-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 sixth gear. The electronic transmission control is optimised to change gear more dynamically. 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 20 kg 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

Built for serene speed

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 20 mm lower than standard. On the S8, ground clearance is varied in three stages between 125 mm in the comfort mode and 95 mm 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 335 mm 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

Discreet sports style

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 S8, too, is supremely athletic yet never aggressive in outlook. 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

Attention to detail

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

No compromises

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

Luxury with new accents

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 sporty, deluxe equipment of the Audi S8.