Audi R15 TDI: Up close

Peugeot beware: Audi has gone to town on its new Le Mans 24 Hours challenger.

The R15 TDI is new in every area, from the weird-looking aerodynamics at the front, through its V10 turbodiesel engine, to the gearbox at the rear. That has to be bad news for anyone looking to usurp the German manufacturer as the undisputed King of La Sarthe. If it could win Le Mans last year with the ageing, even outmoded R10, then what chance for its rivals against this car?

The R15, which goes head to head with Peugeot's 908 HDi on its race debut in this weekend's Sebring 12 Hours, is variously described by the key players at Audi Sport as "a big step forward", "all-new in every respect" and "an entirely new concept".

Perhaps more worryingly for Peugeot, "it does all the things that the R10 didn't do", according to 2008 Le Mans winner Allan McNish.

The R10 broke new ground. After all, it was the world's first purpose-designed diesel racing car. It was radical in that sense, but conservative in many others. Or, in the words of Audi Sport engine boss Ulrich Baretzky, "conventional and courageous at the same time".

Audi went with a V12 engine configuration for the R10 because building a diesel racing engine was a step into the unknown. As a result, it ended up with a long and heavy powerplant that compromised the car's handling. Audi Sport technical director Wolfgang Appel concedes that there was no attempt to push the envelope on chassis development.

"No one knew where the problems would be with a diesel-powered car and for that reason all the other components were within the range of what we knew," he says. "That's very different to this car."

Tom Kristensen during practice for the 12 Hours of Sebring © LAT

Audi Sport boss Wolfgang Ullrich describes the R15 as "a totally new concept, even if it is not our first diesel". Ask him what has been carried over from the R10 and he has to think about it: "Good question. Erm. The wheel nuts, I think."

There was no other choice for Audi but to build a new car for 2009. What's more,
it knew it had to be inventive if it was to close the clear performance advantage enjoyed by Peugeot at Le Mans last June. A well-driven 908 had routinely lapped the Circuit de la Sarthe up to four seconds quicker than the best of the R10s in last year's race.

The writing was on the wall for the R10 from the moment Peugeot arrived on the scene with its 908 HDi in 2007.

A new LMP1 for 2008 was never a possibility, because there was the little matter of developing a new DTM car, the R14. "The capacity we have means that it would have been nearly impossible to do two major projects," says Ullrich. "But when we took the decision not to build a new car for 2008, it was clear that we would have to do one for 2009."

The programme

The fact that the R15 is scheduled to race just twice this season is something Ullrich insists he is "not happy about". Audi's withdrawal from the ALMS after nine seasons - and nine drivers' and nine manufacturers' titles - must have been particularly galling for Audi because the R15, unlike its predecessors, has been designed with the demands of racing in the US in mind.

"It is easy to see that the car has been developed to be fuelled from both sides," explains Ullrich. "Only in America do you have anti-clockwise tracks and that means there is an advantage to being able to refuel on the left. There are other things as well."

Reports that the Joest team will return to the ALMS for the final two races at Road Atlanta and Laguna Seca have been denied by Ullrich. He insists that comments made by Audi chairman Rupert Stadler have been "interpreted optimistically. This is not planned at present. If there are to be any additional races we need to find additional money, and at the moment we are not talking about increasing budgets."

Aerodynamics and engine

The rear wing support of the Audi R15 © XPB

The R15's front end ensures the new car isn't a thing of beauty. Appel confirms that Audi has followed the Formula 1 practice of venting the raised nose to "create low pressure at the front and increase downforce".

Audi has opted for the same top-mounted rear wing as Acura, where it is dubbed a 'quiller'. Appel explains that there is an advantage to mounting the wing from above because of the step angle at which a 2009-spec wing needs to be mounted to achieve the necessary downforce. "Because the wing is narrower and the profile length shorter, you have to incline it more than normal," he says.

Baretzky and his team at Audi Sport's engine headquarters in Neckarsulm were charged with producing an engine smaller and lighter than the existing V12. That led to the decision to do a V10.

There are two reasons why Audi has been able to lose two cylinders in the name of size and weight. "We have gained so much experience with the V12 that we could contemplate making the same power with 10 cylinders," says Baretzky. "The second reason is that we knew the day would come when there would be a cut in the restrictor size for diesels and a cut in maximum power.

"That came last September and it made our job easier."

Driving the R15

"Let's put it this way: I had a smile on my face after my first lap in the car," says Allan McNish. "The R15 did everything I wanted it to do, all the things the R10 didn't do."

The longer-wheelbase R15 is a more nimble racing car than its predecessor, according to McNish.

"It's a lot more agile," he says. "It has a more positive front end, which suits my driving style." On the other hand, "it is still very much an Audi," he says. "You could tell from the moment you got in the car that it was designed by the same group of people."

Take a closer look at the R15 TDI in this week's AUTOSPORT magazine, which also contains a comprehensive 55-page guide to the 2009 Formula 1 season and a fascinating in-depth preview to this weekend's Sebring 12 Hours.