The Audi A8: Engines

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August 28, 2007

Source: Audi AG

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Power, refinement and efficiency

Supreme power for superior road performance, spontaneous handling characteristics with exemplary efficiency – the engine range, too, lives up to the standards of the sportiest saloon in the luxury class. Three six-cylinder and two V8 powerplants, three FSI petrol units and two TDI diesel versions provide a variety of options – according to personal requirements and preferences. The high-end models are equipped with two top-class powerpacks – the Audi A8 W12 features the twelve-cylinder as the epitome of luxury driving and the Audi S8 the fascinating, high-revving V10.

At the other end of the engine range, the new 2.8 FSI demonstrates how well the Audi A8 combines travelling comfort with excellent efficiency and low fuel consumption. Thanks to this ultra-modern engine and the exemplarily low vehicle weight of only 1690 kilograms the standardised fuel consumption of the A8 2.8 FSI is a mere 8.3 litres per 100 kilometres. This corresponds to CO2 emissions of 199 grams per kilometre – the lowest figure in the luxury segment.

This level of efficiency does not entail any form of compromise. The V6 engine develops 154 kW / 210 bhp and produces its maximum torque of 280 Newton-metres across a wide engine speed range from 3,000 to 5,000 rpm. The favourable weight of the vehicle, made possible by the ASF aluminium construction, and low aerodynamic drag also affect the dynamics: with an acceleration time of only 8.0 seconds and a top speed of 238 km/h the A8 2.8 FSI undoubtedly delivers a supreme driving experience.

Advancement through efficient technology

The new six-cylinder engine demonstrates its Vorsprung durch Technik with FSI petrol direct injection and the innovative Audi valvelift system. The new technology has the purpose of controlling valve lift variably in two stages. The Audi valvelift system implements so-called cam pieces, located on the intake camshafts, which can be moved and controlled electronically.

They carry two cam contours, side by side, for small and large valve travel. The valves are opened according to load requirements and depending on the position of these cam pieces.

The advantage: the fresh mixture required can be controlled much more accurately via the valve opening; the throttle valve remains open longer and so-called throttle losses decrease. In conjunction with a number of additional measures to promote reduced friction at numerous components, the Audi valvelift system cuts fuel consumption by ten per cent.

FSI for optimum utilisation of energy

FSI technology is also featured on the two other petrol engines in the Audi A8: the powerful six-cylinder 3.2 FSI and the potent 4.2 FSI V8 use petrol direct injection and the optimum combustion this affords for remarkably impressive pulling power from all engine speeds along with maximum utilisation of the energy in the fuel.

In terms of design, like all six and eight-cylinder units in the A8, they belong to the current family of V engines with a 90-degree angle, which – with a cylinder spacing of 90 millimetres – is remarkable for its compact dimensions and low weight. The 3.2-litre V6, for instance, is a mere 360 millimetres in length and weighs 169.5 kilograms.

The 3.2 FSI develops 191 kW / 260 bhp, its maximum torque of 330 Nm being available at 3,250 rpm. However, more than 90 per cent of this maximum torque is provided over a wide range between 2,400 and 5,500 rpm – a unique feature for naturally-aspirated V6 engines. Acceleration time is 7.7 seconds, top speed is 250 km/h and standardised fuel consumption is 9.9 litres.

V8 with superior performance

Even at the dawn of the automotive industry, eight-cylinder engines were highlights in the Audi range. The Audi Type R of 1928, for example, housed a 4.9-litre eight-cylinder inline engine under its long bonnet. The inline layout has not been maintained for some time, of course. Today, the modern V engines from Audi, even those with eight cylinders, are extremely compact and feature cutting-edge technology: the cylinder housing is cast from an aluminium-silicon alloy; the pistons and rings glide in the liners on hard silicon crystals. The V8 draws its intake air through a two-stage variable intake manifold made of magnesium.

Delivering 257 kW / 350 bhp at 6,800 rpm, the 4.2 FSI has impressive perfor-mance potential; its maximum torque of 440 Nm guarantees superlative pulling power – especially since 85 per cent of it is available from as low as 2,000 rpm. For the sprint to 100 km/h the Audi A8 4.2 FSI requires a mere 6.1 seconds; the governed top speed of 250 km/h is quickly reached. Standardised consumption of the V8 is 10.9 litres.

TDI units with muscular pulling power

The two TDI engines in the A8 range are fascinating in their own particular way – with mighty pulling power and impressive performance together with fuel economy. Six and eight-cylinder versions operate with common rail injection systems and particularly fast-acting piezo injectors. These are able to precisely distribute minimum amounts of fuel to the combustion chambers within milliseconds. This means that the number of injection processes per cycle can be varied and optimised virtually at will, resulting in optimum combustion control.

This strategy efficiently reduces emissions and ensures smoother engine operation. In this area the 3.0 TDI and 4.2 TDI are undoubtedly among the best diesel engines in the world. Audi, the inventor of the TDI, is continuously extending its Vorsprung durch Technik.

Even the A8 3.0 TDI achieves powerful performance figures with its six-cylinder engine. Thanks to an output of 171 kW / 233 bhp, it reaches the 100 km/h mark from a standstill in only 7.8 seconds, its top speed being 243 km/h. Its maximum torque of 450 Newton-metres, which this engine delivers from 1,750 rpm, is naturally even more impressive. The standardised consumption of the 3.0 TDI is 8.5 litres per 100 kilometres.

4.2 TDI with the dynamics of a top athlete

The current king of the TDI range from Audi is the V8. With a mighty output of 240 kW / 326 bhp and enormous torque of 650 Newton-metres from as low as 1,600 rpm, the Audi A8 4.2 TDI offers the dynamic performance of a professional athlete. The saloon sprints in just 5.9 seconds to a speed of 100 km/h; its top speed is governed at 250 km/h. When compared with the performance potential it offers, its standardised consumption of just 9.4 litres is extremely modest.

In line with the lightweight construction concept of the Audi A8, the 4.2 TDI is one of the lightest diesel V8s ever: the entire engine weighs only 255 kilograms. In addition, its very short overall length of only 520 millimetres improves weight distribution in the vehicle. Both qualities are of prime importance for the handling characteristics of the Audi A8.

The V8 TDI owes its spontaneous response and excellent torque development to the two turbochargers with variable turbine geometry – the maximum speed of the turbine wheels is over 210,000 rpm, incidentally. Both intercoolers are positioned below the front headlights for optimum air flow. Mixture preparation is performed by a latest-generation common rail system: here, too, piezo inline injectors are employed.

quattro drive offers reserves for every situation

The quattro permanent four-wheel drive on the Audi A8 provides the assurance that this enormous power will be transmitted to the road without any losses. Particularly with respect to the torque delivered by the TDI engines or the V8 FSI, the drive system provides the necessary reserves of traction and safety across all four wheels, in all driving situations and on all road surface conditions. It ensures excellent grip and directional stability and guarantees maximum driving enjoyment with a high level of active safety. The centre differential automatically undertakes dynamic torque distribution, adapting it to the prevailing situation within milliseconds. If a high level of wheel spin is detected, the quattro drive is assisted by the electronic differential lock (EDL). If necessary, propulsive power can be concentrated on one wheel.

Superior driving comfort and almost imperceptible gear shifts are provided on quattro models by the six-speed tiptronic with the dynamic shift programme. In addition, the gears can also be changed manually via the gearshift lever or by means of optionally available paddles behind the steering wheel.

In combination with front-wheel drive, the continuously variable automatic transmission multitronic is used on the 2.8 FSI and 3.2 FSI models. With its completely jolt-free acceleration it not only offers unprecedented driving comfort – with its wide overall ratio it permits a very economical driving style, while still retaining its athletic qualities with the seven fixed transmission stages in manual mode. The 3.2 FSI is optionally available with front-wheel drive or quattro drive; the 2.8 FSI features front-wheel drive.

The equipment, data and prices stated here refer to the model range offered for sale in Germany. We reserve the right to make changes. Errors and omissions excepted.

Article Index:

At-a-GlanceDesign and InteriorBodyEnginesChassisAssistance SystemsMultimedia SystemsEquipment and TrimCustomisationAudi A8 W12Audi S8Audi A8 W12 Security

D3 Audi A8 Photo GalleryD3 Audi S8 Photo GalleryAudi A8/S8 Discussion Forum

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