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Audi R8 Diesel

What on earth is a mid-engined supercar capable of 186mph doing on Green-Car-Guide? Well, we’ve made no secret from the start that we want to see great cars that are also green. Is the Audi R8 a great car? Absolutely. It looks fantastic (this concept has a different grille from the petrol R8), it drives like no other Audi, or any other car for that matter, and because of that it has won a whole host of motoring awards and recognition since its launch.

So is it green? Well, this is a ground-breaking car (still a concept but likely to go into production within the next 18 months) as it’s the first supercar with a diesel engine. No fuel consumption or emissions figures are available, however it’s likely that it may manage around 25mpg combined rather than the 19.3mpg of the petrol V8. This would represent a 25% improvement in economy – which is surely good in anyone’s books.

A supercar that complies with EU6 emission limits

However the story doesn’t stop there. The R8 6.0-litre, 12-cylinder TDI engine (first seen in the forthcoming Q7 V12 TDI) already complies with proposed EU6 emission limits expected to apply from 2014 thanks to highly efficient common rail injection with piezo injectors, twin particulate filters and new ultra low emission system.

The heart of the system is a special catalytic converter downstream of the oxidizing catalyst and the particulate filter. The second component is an additional tank containing an aqueous urea solution. Small quantities of the solution, known as “AdBlue,” are injected into the exhaust system. The hot exhaust gases break the solution down to form ammonia that splits the nitric oxides into inert nitrogen and water. The system remains effective for the entire service life of the vehicle.

The car is also relatively lightweight due to Audi’s Space Frame (ASF) construction, mating lightweight aluminium panelling to an aluminium space frame.

And there’s more. We normally don’t talk much about torque on Green-Car-Guide. But we have to make an exception in the case of this car. The petrol V8 R8 develops 317lb ft of torque (at 4500rpm). The V12 TDI develops more than double this figure, with an earth-moving 738lb ft – or 1,000Nm – at just 1750rpm. Oh, and almost 500bhp. And all this with improved fuel efficiency.

Of course it should be no surprise that Audi is offering us a diesel R8 after their wins at Le Mans in 2006 and 2007 with the R10 TDI. The R8 engine which is derived from the racing car is a twin-turbo and reaches 62mph in just 4.2 seconds – 0.4 of a second faster than the petrol V8. And because the diesel engine is a relatively compact unit, it fits successfully in the R8’s engine bay. A six speed manual gearbox is used rather than the DSG, which isn’t strong enough to handle the huge torque.

The car has Audi’s legendary quattro permanent four-wheel-drive reassurance, thankfully with rear drive bias, together with Audi’s magnetic ride adaptive damping system – clever technology that helps it go round corners in a way that few other cars can match.

The R8 V12 TDI Concept debuted on Press Day at the North American International Auto Show on January 13th.