Audi has stolen a march on every other sports car manufacturer by unveiling the world’s first diesel supercar. The R8 V12 TDi, seen for the first time today at the Detroit motor show, could kick starts a new era of performance diesels; it is faster, more powerful and has much more torque than the petrol-powered R8.Powered by a 5.9-litre 12-cylinder twin-turbo diesel with 738lb ft and 493bhp, the R8 V12 will crack 62mph in 4.2 seconds. That’s a symbolic 0.4sec faster than the petrol R8, but torque is increased by a much more noticeable 421lb ft, and power goes up by 79bhp. The engine, the same unit used in the forthcoming Q7 V12 TDI, is derived from the diesel used in Audi’s Le Mans-winning R10 circuit car. Because the V12 is a relatively compact unit, Audi’s engineers have been able to slot it into the R8’s mid-mounted engine bay. And by using a stronger type of cast iron than usual, they have cut the thickness of the cylinder walls which helps to reduce the engine’s weight. Although there are no emissions figures for the car, Audi claims it will meet the forthcoming Euro 6 regulations due in 2014. The engine uses the AdBlue injection system, which adds urea to the exhaust to cut nitrogen oxide emissions.Audi has fitted a six-speed manual gearbox to the diesel R8 – its DSG transmissions are not yet strong enough to deal with the V12’s torque – which should create a unique driving experience.The car’s bodyshell is standard R8, but Audi has added a glass roof with an air intake for the engine in the middle. Like the Q7 V12 TDI, the R8 diesel gets its own front bumper design, replacing the petrol car’s two piece grille with a deep one-piece item and adding new side intakes with a honeycomb mesh. At the rear the exhaust pipes have moved up into the cooling vents, there’s a new rear bumper design and, for the first time on an R8, a spoiler. Inside the car is mostly standard-issue R8, with some added carbon fibre and aluminium trim. Although billed as a concept, expect a production version to go on sale within the next two years, shortly after the naturally aspirated V10 petrol version arrives.