The car you see here may well be the future of high-performance motoring. It can exceed 186mph, shoots from 0-62mph in 4.2sec and will carry a price tag that’s a match for a Ferrari or an Aston. The big difference between those cars and it, however, is that this is a diesel. In an audacious move that would have seemed sheer fantasy just a few years ago, Audi has created the world’s first diesel-powered roadgoing supercar – the R8 TDI. But in view of the fact that diesel-powered Audi racers have driven to victory at Le Mans for two consecutive years now, this isn’t so fantastical.

This concept car is based on the production Audi R8, and looks little different from it. Seen from the front, though, it’s obvious that it has deeper air intakes at either side of the radiator grille, and with its slotted air vents the TDI’s rear end is more dramatic. Squint at the car side-on, and you’ll also notice the addition of decorative aluminium strips along the door sills.

Then there’s the big duct mounted in the roof. This is needed because the twin-turbo engine has two intercoolers, which the side vents, that normally feed air to the engine, are redirected to supply. Audi’s engineers had to find another way of sending air to the engine, and the roof duct is their solution to the problem.

The TDI’s headlights are also different, and of the LED type. Audi claims this is a world first, and intends to make the lamps available as an option on the petrol R8 later this year. The light from LED lamps is said to be much closer to daylight, and makes night-driving less tiring.

It’s the engine, however, that really sets this supercar apart. Usually I associate “diesel” with the smell that hangs over Dover docks or the asthmatic clatter of London’s black cabs, but not with supercars. The decision to go for diesel power tends to be one made with the head rather than the heart.

Of course, this diesel engine, a development of the Le Mans-winning V12, is no ordinary one. From its six litres it develops 500bhp and 738 lb ft of torque. Although this might is shunted through a six-speed manual gearbox, Audi reckons a production TDI would more likely use a seven-speed sequential box. Naturally, the drivetrain is quattro 4x4.

The R8 TDI’s cabin is surprisingly spacious, and the fascia includes an instrument cluster that is unique to the diesel. The glass roof makes for a light and airy environment, although production models are unlikely to have it.

I stood behind the TDI as a colleague fired it up, and while the visual cues of brutal exhausts and myriad vents made me expect Wagnerian noises sufficient to blow me off my feet, the reality was more Enya than Wagner – a high-pitched giggle from the starter followed by a soft-edged whirring. Big particulate filters in the exhausts muffle much of the aural fury, and do their job well as there was no hint of diesel smoke visible either at startup or at any other time.

I chuckled at the absence of drama when the big diesel murmured gently to itself once I’d stabbed the red starter button. I was amazed at how refined this engine is, and how responsive it is to the throttle. It didn’t feel in the least like a diesel, and the sound inside the cabin was more a turbine-like hum than the roughness I’d expected. It was anything but unpleasant and nothing announced the engine’s oil-burning roots, while the massive torque (limited in this instance to 369 lb ft, but that’s still huge) allowed me to pull away at as little as 500rpm with no judders or bunny-hops.

Audi’s insistence that we keep to a maximum speed of 50mph very much limited the road test, yet my drive was enough to reveal that the TDI lacks one crucial supercar trait – the ability to reach the heady rev-ceiling of a powerful petrol engine (the TDI calls time at 5000rpm). Rev a Ferrari F430 beyond 7000rpm for the first time, and I swear that sound will remain with you for ever. By comparison, the TDI’s visceral impact is not nearly so memorable, although Audi says it is working on improving the engine’s aural qualities.

So what is the purpose of this diesel? Audi says it will return a combined-cycle fuel consumption of 28.5mpg and will therefore be a supercar that is CO2-friendly. Supercar drivers will no doubt respond with a “So what?”, but Audi is confident that customers will flock to the TDI, attracted by its huge torque and the fact that it will be considerably quicker than its V8 sibling despite a 110kg weight penalty. And let’s face it, its uniqueness in the supercar domain will make for fascinating conversation.

Audi will decide this summer whether to put the R8 TDI into production, but already customers are queueing to put down a deposit.

Vital statistics

Model Audi R8 TDI Le Mans

Engine type 5934cc, 12 cylinders, twin turbodiesel

Power/Torque 500bhp @ 4500rpm / 738 lb ft @ 1750rpm

Transmission Six-speed manual

Fuel/CO2 28.5mpg / 250g/km

Performance 0-62mph: 4.2sec / Top speed: 186mph-plus

Road tax band G (£300 for 12 months)

Price tba

Verdict Another mad concept from the Veyron people

Rating

Date of release: 2010 (estimated)

The opposition

Model Lamborghini Gallardo £126,350

For Sensational 520bhp V10, fabulous dynamics

Against Getting long in the tooth, big blind spots to rear

Model Ferrari F430 £129,000

For Race-bred heritage, real sense of occasion

Against Draws a bit too much attention

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