Click for High-Res Photo Gallery: 2009 Audi R8 Le Mans Concept For those who recall the bad old days of the American diesel, the 2009 Audi R8 Le Mans might seem like a contradiction in terms.

Ask most Americans to describe diesel power and they're likely to use words like "slow," "smelly," or "rough-riding." Yet if you listen to the German automaker, the best way to describe the latest version of the R8 sports car, which is making its debut at the annual Geneva Motor Show, would be "clean and mean."

The Brilliant Red two-seater on the Audi show stand is a direct descendant of the R10 race car that has been sweeping the global endurance circuit, including the legendary 24 Hours of Le Mans , from which it, appropriately, takes its name.

And its attitude. In the engine compartment, the original R8's competent gasoline engine has been replaced with a 6.0-liter V-12 turbodiesel. The horsepower numbers, at 500, are impressive. At 738 pound-feet, torque is downright menacing. In European trim, that translates into a top speed of just under 300 kmh, or 186 mph. And the Le Mans will launch from 0-100 kmh (0- 62.5 mph) in just 4.2 seconds.

The engine makes heavy use of the knowledge Audi racing engineers have gained trackside - from the decision to go with a 60-degree angle of the cylinders to the piezo-electric fuel injectors. The engine employs chain-driven camshafts and a chain-driven oil pump and is made of high-strength aluminum with a cast-iron-and-graphite crankcase. A pair of turbos provides a hefty 37 psi boost. And the latest emissions system ensures that the R8 Le Mans meets the tough new Euro 6 standard. (And would almost certainly be ready to comply with California 's tough diesel regulations.)

As TheCarConnection's Bengt Halvorson first reported in January, Detroit 's silver R8 diesel was "covered in a special matte "Grace Silver" bodywork, and gets accentuated wheel arches and larger air openings relative to the standard R8, along with a rhombus pattern on the air inlets and outlets similar to those used on the RS vehicles. Another noteworthy feature is the race-inherited NACA ductwork in the middle of the roof, which brings cooling airflow down and across the engine's cylinder banks."

"The V12 TDI also differs from the R8," we first reported, "with its glass roof, restyled rear glass lid, and new air deflectors. Like in the R8, the engine bay can be displayed with special LED lighting."

So what's changed? There's the new name, of course, and the Brilliant red paint job. Technically, the twin-turbocharged Le Mans is still a concept vehicle, a slightly renamed version of what we first saw at the Detroit Auto Show, in January. But well-placed sources tell TheCarConnection.com that a formal decision on production is approaching fast, and it would take some serious, as yet-unforseen obstacles, to scuttle the program.

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2008 Audi R8 TDI Concept by Bengt Halvorson (1/13/2008) Is this street-legal Le Mans racer destined for driveways?

2008 Geneva Motor Show Coverage (3/4/08) The year's first big European auto show makes plenty of news.