Audi has revealed that its bid to retain the Le Mans 24 Hours crown it has made its own over the past few years will come from a diesel-engined sports prototype, confirming speculation that it would join Peugeot in switching over from regular race fuel.

Unlike the French marque, however, Audi intends to be on the grid - and winning - at the 24 Hours in 2006, after the much-anticipated R10 was unveiled in Paris today [13 December]. And, as if to prove that the new car is ready to take up where the venerable R8 left off in June, seven-time Le Mans winner Tom Kristensen took time out from the presentation to drive the R10 on a closed section of public road in the shadow of the Eiffel Tower.

Audi first raced at Le Mans in 1999 and, after a difficult debut, went on to win the classic five times in the last six years, with R8 adding to the 56 victories it had taken from 77 appearances in sportscar series around the world.

Next season, however, sees Audi venture into previously unexplored terrain with the V12 diesel powerplant, which will be manufactured completely from aluminium. The all-new engine will be a 5.5-litre twin-turbo TDI powerplant, producing over 650bhp and a colossal 1100 Newton metres of torque. Car and engine are expected to make their competitive début in the Sebring 12 Hours next March, before preparing for Le Mans race in June.

The prototype V12 is expected to be quieter than expected thanks to its smooth running, but the engine's unique specification still presented Audi Sport engineers with many new challenges. The injection pressure will easily exceed the 1600 bar achieved in production cars, but the usable power band will lie between 3000-5000rpm, unusually low for a racing engine. In addition, the drivers - when announced - can expect to change gear far less often in the new car than in the out-going R8 because of the TDI engine's favourable torque curve.

“With the A8 4.2 TDI quattro, Audi already builds one of the most powerful diesel road cars in the world,” explained Prof Dr Martin Winterkorn, “Nowadays, every second Audi is delivered with a TDI engine, and the Le Mans project will help our technicians to extract even more from TDI technology. We expect that the percentage of diesel engines will be even larger in the future.”

Radical changes to the chassis were also necessary, as the R10 will have a significantly longer wheelbase than the R8, while the overly wide front tyres are, up until now, unique for a Le Mans prototype. New technologies were also implemented during the development of the carbon-fibre monocoque, with chassis, engine and gearbox forming an extremely rigid, fully stressed unit.

“The R10 project is the biggest challenge ever to have been handed to Audi Sport,” admitted head of motorsport Dr Wolfgang Ullrich, “TDI technology has not been pushed to its limits in motorsport yet, so we are the first to confront the challenge. The demands of such a project are accordingly high, but long-term technology partners such as Bosch, Michelin and Shell are supporting us in our quest. Together, we will have the chance to write new chapters in the history books of motorsport and diesel technology.”

The new Audi R10 has already tested, successfully completing its first outing at the end of November, but an extensive development programme - in the hands of Audi Sport and Team Joest - is scheduled prior to the car's race début at Sebring.