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Audi A8 4.0 TDI Quattro



THE new 4.0-litre V8 diesel in Audi's flagship A8 is a masterpiece of engineering.

Audi's new A8 4.0 V8 TDI quattro, a car that will make even the most hardened petrol-head look at diesels in an entirely new light. The look of the new A8 isn't anything that will take the art world by storm with its subtle, muscular stance and slightly bland front end.

Its aim is to provide subtle good taste, rather than offer a show of wealth that might be achieved with some rival models.

Under the bonnet, the V8 3,936cc engine is just as understated – a gleaming silver mound resting in an otherwise uninterrupted sea of black.

Buyers of this car who decide to lift the bonnet themselves will see a small piece of history, because this is the first V8 diesel to be offered for sale in the UK. Audi has produced V8 diesel units before, namely a 3.3-litre unit also used in the A8, but this never came to Britain.

The decision to bring the V8 engine in with the latest model is clearly a vote of confidence in demand for diesel among luxury car buyers, most of whom will be buying with company money to afford the price tag that is likely to be around £50,000.

For your money you get more than a piece of history. The engine offers 275bhp at 3,750rpm (compared to the 4.2 petrol model's 330bhp) and delivers 478lb-ft of torque between 1,800 and 2,500 rpm (the 4.2 petrol achieves 317lb-ft).

The common rail system pressurises fuel to 1,600 bar, equivalent to the weight of a mid-size saloon car resting on your fingernail, to atomise the fuel when it is injected into the cylinders and give better fuel air mixing and more efficient combustion.

The immense power on tap is created with the help of two turbochargers backed by two intercoolers and by pushing power down through all four wheels, it can hit 62mph in 6.7 seconds – making it the fastest diesel saloon car in the world – and just a shade behind the 4.2-litre petrol's 6.3 seconds time for the benchmark sprint.

As well as being the highest torque Audi production car, it is also the highest-powered, highest torque V8 diesel engine in any production saloon car.

You certainly get the idea Audi wants to make a big impression with this engine, which will take 15% of UK A8 sales, and it goes a long way to achieving the goal of making sceptics look at diesel in a whole new light.

Economy doesn't need to enter the equation (29.4mpg combined, by the way), comparing well with petrol A8s and rivals. The diesel makes a hugely strong case for itself without considering economy.

At first, engines will only meet Euro III standards, as extra particulate filters will need to be added to achieve Euro IV standards.

It is incidental anyway, as CO2 emissions are 259g/km, so even without the 3% tax penalty for not meeting Euro IV, drivers pay benefit-in-kind (BIK) tax at 35% of P11d price.

Equipment levels have yet to be confirmed, but expect a six-speed automatic box, variable speed power steering, power everything else, and a high performance braking system.

Behind the wheel

DIESEL seems to be particularly suited to a V8 engine when it comes to making a good first impression. Most V6 diesel engines have the slightest hint of 'truck' about them at start-up, but there is something about the throaty warble of a V8 engine at tickover that helps mute any heavy-oil tones in this car.

Rev the engine slightly and they disappear altogether, replaced by the wonderful burbling of a sporty, powerful engine ready to let loose. However, to hear any of this you need to be outside the car because there is barely any hint of engine noise at all inside the leather-clad interior.

During our drive out to the Buchheim Museum, a brief stint of cut-and-thrust city motoring followed by fast motorway driving outlined two important factors about this car.

Firstly, it offers such vast amounts of power that drivers can simply demand speed from the accelerator and the car will have them there as fast as they can think it. Turbo lag doesn't come into the equation, thanks to variable geometry units which spin at 210,000rpm. For city driving this is ideal, with the car launching to 40mph or 50mph in what feels like an instant.

On the downside, this car could help drivers to lose their licences very quickly. The engine's immense torque means it never needs to exceed 3,000rpm, so the car doesn't sound as though it is racing along. Even topping 140mph on the German autobahn, it is only running in the mid-3,000rpm range. Inside it is quiet enough to feel like 70mph.

The throttle also feels too touch-sensitive, so B-road driving can be a jerky experience, as even small touches of the pedal produce a great shove of torque, rather than a gently increase in speed. But with cruise control switched on, that shouldn't be a problem. As the engine only weighs 270kg, having a diesel lump in the front doesn't seem to affect handling. It is surprisingly agile for such a large car.

Driving verdict

PHENOMENAL mid-range power is what this big Audi majors on. With so much torque on tap, the A8 can munch miles with ease, all while wafting its occupants along in luxurious, leather-lined comfort. In performance and tax, it differs little from the petrol V8 models, but fuel stops will not be as frequent.

Make: Audi
Model: 4.0 TDI V8
Max power (bhp/rpm): 275/3,750
Max torque (lb-ft/rpm): 478/1,800
Max speed (mph): 155 (limited)
0-62 mph (secs): 6.7
Fuel consumption (mpg): 29.4
Fuel tank capacity (l/gal): 90/19.8
Transmission: 6-speed auto
Service intervals: variable
On sale: deposits being taken
Price (OTR): c.£50,000

CO2 emissions and fuel consumption data correct at time of writing. The latest figures are available in the Fleet News fuel cost calculator and the company car tax calculator.

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