It's one of the world’s sexiest cars – and now the Audi R8 is even more special. Because beating beneath the dramatic rear glass cover of this version is a diesel engine!

The 6.0-litre V12 isn’t just one of the fastest oil-burners the firm has ever built – it means the R8 is the quickest, most powerful car of its type on the planet, too.

Unveiled first as a working prototype at this year’s Detroit Motor Show, the 500bhp two-seater also appeared at Geneva in March, painted a brilliant red.

According to Audi, the colour was a matter of much internal debate. Originally the R8 was finished in silver, but after a single outing for the cameras, red was chosen to highlight its diesel performance credentials.

Combined with a unique smoked chrome finish for the air intakes and aerodynamic aids, the new colour scheme is inspired by the distinctive red and silver of Audi’s Le Mans-winning diesel endurance racers. It’s a fitting tribute, too.

From a distance, the R8 V12 TDI looks similar in all but detail to its petrol-engined brother. But in reality, the two cars could hardly be more different.

Only the front wings, A-pillars, roof rails and rear three-quarters have survived the transformation untouched – such is the impact of fitting a huge engine in the compact dimensions.

As a result, the TDI has a new engine cover, wider air intakes, a revised rear wing and more aero-dynamic parts added to the sills. Blade-like spoilers within the intakes up front help to complete the changes, while at the very core of the design is another intake mounted on the roof.

The opening is inspired by the same detail on the 1991 Audi Avus concept car and supplies cool air to the twin intercoolers via carbon fibre manifolds.

As the V12 is 60mm longer than the petrol V8, engineers also had to find extra space in the already compact engine bay. They did so by removing the bulkhead and replacing it with a new one specially shaped to wrap around the front of the diesel powerplant.

As a result, cabin space is marginally reduced, and there is no longer any storage at the rear of the car. The bigger motor also presents another unique challenge for visibility out of the back. The unit is so large you can see virtually nothing through the rear view mirror – so a reversing camera has been added to the adjustable wing.

The pedigree of the V12 itself makes all of that worthwhile. The twin-turbo unit is closely related to the engine that powers the R10 Le Mans winner, and it produces 1,000Nm of torque from only 1,750rpm.

Capable of firing the car from 0-62mph in only 4.2 seconds and on to a top speed of 200mph, this R8 is even faster than the petrol V8 machine on which it is based. To ensure the driver is well aware of this, there have been major changes inside. Most noticeable are the new red anodised instruments, but there is also lightweight leather for the dash, and a red wheel-mounted starter button.

One press primes the ignition – the second starts the V12. Despite the size and design of the unit, it spins into life eagerly with mechanical chatter, although the engine note is strangely muted. There’s no soaring wail as the revs climb, just a clinical, metallic buzz. However, it’s eager to respond.

To pull away from the line, simply slot first gear, and lift the throttle. The idle speed is set to 600rpm, yet even at this pace the unit serves up so much torque it will actually drive the R8 right the way into fourth gear without the need to touch the accelerator and by only using the clutch.

Under full throttle, vast amounts of air are gulped through the intakes, creating a dramatic roar in the cabin. From 1,750rpm, the Audi really begins to surge forward – and although our test drive saw the output of the engine limited in order to preserve the A4-sourced gearbox, it’s still clear that what this unit lacks in aural appeal, it more than makes up for with raw power.

The big V12 promises to be green, too. It features Audi’s Adblue technology, which treats the exhaust gases with urea to reduce nitrogen oxide emissions. As a result, the unit will meet the standard expected of Euro VI pollution laws scheduled to be introduced in 2010. As in the standard car, the steering is accurate and the ceramic brakes are powerful.

However, there’s one last feature of the V12 that’s likely to appeal to keen drivers – the firm’s Dynamic Drive system. This set-up balances suspension, throttle and engine settings according to the driver’s wishes. And in the V12 R8, it’s controlled via a Ferrari-style knob mounted on the steering wheel spoke.

The system switches between dynamic, sport and race modes, which progressively harden the Magnetic Ride suspension and sharpen throttle response to up the pace.

So, the only question left is when the R8 TDI will go on sale. For the time being, Audi is tight lipped, but it acknowledges that it has a very real chance of making limited production, possibly as early as 2010.

One thing is for sure – given the huge performance, its status as the world’s first true diesel supercar, and its spectacular design, there will be no shortage of eager drivers desperate to get behind the wheel.

FIRST OPINION

• The R8 V12 TDI is not only spectacular, it’s a piece of history. As the world’s first diesel supercar it has finally broken one of motoring’s biggest taboos – namely that roadgoing racers shouldn’t have oil-burning engines. The installation of such a huge powerplant obviously delivers impressive pace, but we still can’t help but feel that the car could do with a better engine note... something which Audi will hopefully address.

AT A GLANCE

• Price: £100,000 (est)

• Engine: 6.0-litre V12, 500bhp

• Transmission: Six-speed manual, four-wheel drive

• Kerbweight: 1,590kg (est)

• 0-62mph: 4.2 seconds

• Top speed: 200mph (est)

• MPG: 27mpg (est)

• Standard equipment: Dynamic Drive system, Bang & Olufsen sound system, racetrack navigation, carbon and lightweight leather trim
  

• On sale: Now

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Wow, this car is incredibly good looking. It is the first time I am liking the R8

The car is very nice and is as expected. There is only one thing that kind of bugs me though. Not a whole lot, but it still bugs me a bit. What? The front end. I'm not too fond of those fins. In some angles they mix well with the design, in others they look tacky.

Those pictures were taken in Miami, how come I NEVER see them doing this! Whether it's the R8, or the Ocean Drive MB concept...

Nice review!

Is it just me who isn't convinced with 27 MPG? When you get to this market I can't see diesels selling since the cost of petrol relative to the car is disproportionately low. They might sell just from a novelty standpoint. I think BMW's 6er diesel is more representative of how a diesel and coupe can work. A hotter version of that, maybe with light hybrid, would be amazing and sell.

Those pictures are amazing, makes Diesels look HOT