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  Audi R15 plus TDI

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Country of origin:Germany
Introduced in:2010
Numbers built:4
Internal name:R15
Predecessor:Audi R15 TDI
Successor:Audi R18 TDI
Author:Wouter Melissen
Last updated:December 30, 2010
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Click here to download printer friendly versionIn 2009 Audi responded to the blisteringly quick Peugeot 908 HDI Fap with the revolutionary and controversial R15 TDI. The second generation Audi diesel racer was much of a clean sheet design as its immediate predecessor had been and as a result was a far more homogenous package. All aspects of the design were dominated by the car's DTM inspired aerodynamics. Instead of the air running around the car, the R15 had an intricate configuration that channeled much of the air through the car. It was hoped that the car could generate considerably more downforce than its predecessors without the increasing drag. This was believed to be particularly crucial on the tighter tracks used for the American Le Mans Series.

Unfortunately for Audi and the R15 TDI, the economic crisis hit during a crucial time of its development. One of the consequences of the crisis was a dramatic cut in Audi's racing program for the 2009. With such a trick aerodynamics package, what the engineers and drivers actually needed was track-time and as a result of the cuts and the several rained-out test sessions, they only got a minimum of that. This left Audi uncharacteristically unprepared for the season but that did not stop the team from winning the season opening Sebring 12 Hours against the seasoned Peugeot team. The R15 continued a tradition of new Audi sports racers winning straight of the box, which started with the original R8 back in 2000. The early success was quickly forgotten after Le Mans, which was dominated by arch-rivals Peugeot. The Audi team had not managed to fully get to grips with the R15's complicated aerodynamics.

A further complication was Peugeot's insistence that some elements of the R15's aerodynamics did not comply with the regulations. One of Peugeot's biggest gripes was the adjustable 'wing' mounted between the front fenders and inside the gaping air-intake. The French team filed an official complaint during the Le Mans race week but that was thrown out. The controversy remained and over the winter the ACO clarified the situation with an amendment to the regulations. Although this forced most teams to make changes to their existing cars, it affected the Audi 'channel' design most of all. This was the final push for the German manufacturer to abandon the innovative aero solutions and fall back to a more conventional package for the 2010 season. With the mechanicals and much of the chassis design remaining the same, Audi opted to dub the 'new' car the R15 'plus'.

Over the winter, twenty important aspects of the R15 were redesigned, and because of the regulation changes only came in November a lot of the work had to be done twice. The 'channel' concept was not entirely abandoned but most of the air scooped up is now led out the sides and over the top instead of through the car. The remainder is fed to the radiators inside the side-pods and fed out the back of the car. The radiators themselves have been relocated to improve efficiency. The front itself was also altered almost beyond recognition with a prominent two-part nose grabbing all of the attention. The controversial wing element has been removed altogether with only two legality plates remaining to hide the front suspension from view. The regulation change that affected all teams concerned the area behind the rear wheels, which now have to be masked by bodywork. Audi's solution was to fit louvers pointing up, which feeds some additional airflow to the rear wing.

The revised aerodynamics also required that changes were made to the chassis design, to the extent that it had to be subjected to a new crash test. The double wishbone and torsion bar suspension was left unaltered for the most part. In order to get a better balance between the diesel and petrol engines in the LMP1 class, the ACO lowered the maximum restrictor size and turbo pressure. Careful tweaking of various components of the V10 diesel engine meant that Audi succeeded in keeping the loss of power to a minimum. Standard equipment on all diesel powered Le Mans prototypes, the sturdy XTrac five-speed gearbox also found its way into the back of the R15 plus TDI. The finished product is an altogether more efficient and simpler version of the original R15 TDI, designed with just one target in mind: a victory in the 24 Hours of Le Mans.

Having learned their lesson in 2009, Audi subjected the R15 plus to a rigorous testing program ahead of Le Mans. Due to the late changes to the regulations, the car was not ready to race in the traditional season opener at Sebring. The team was at the track a few days later for an extensive test, which provided the first comparison with also present Peugeot. Back in Europe the new Audi was subjected to high speed tests at Monza, Paul Ricard and on two long straights of the Eurospeedway before making its competitive debut in what Audi described as the first of two test races. A single example was entered for star drivers Allan McNish and Dindo Capello in the Le Mans Series opener, the Castellet 8 Hours. Facing only a privately entered Peugeot, the now traditional debut victory did not give the Audi engineers reason to cheer just yet. What was promising was the reliable run and the newly found straight-line speed.

The final, public 'dress-rehearsal' came nearly a month later at Spa-Francorchamps where the Audi and Peugeot diced it out at full strength; with three cars each. Running the Le Mans aero package, the Audis were at a disadvantage, which was shown in the individual lap times. During the race a shrewd tactical plan almost saw the quickest of the R15 plus TDIs clinch the victory from the Peugeots under changeable conditions. Despite being upstaged at Spa, Audi still arrived at Le Mans as the joint-favourite. Practice and qualifying for the 'big race' were not promising for Audi. Peugeot still had the speed advantage, the French team had held in the past three editions. While the revised Audi certainly was more efficient at speed as its predecessor, the German V10 seemed incapable of keeping up with the hugely powerful Peugeot V12.

During the first half the race things still looked ominous for Audi and a second defeat in a row at Le Mans loomed. Peugeot had lost one car to a crack in the tub at a suspension mounting but still looked as dominant as in 2009. Then, early on Sunday morning, the front running 908 spit a huge flame out of the right-hand exhaust. The other two surviving Peugeots eventually succumbed to the same problem, which was later traced down to a piston failure caused by the engines being run too hard. This handed the race and the entire podium to Audi on a gold platter, showing that outright pace alone does not win endurance races. In the process, the distance record set back in 1971 was shattered. After the race, Audi revealed that the V10s had been fitted with Variable Turbine Geometry (VTG) turbos.

Following the, perhaps surprising, victory in the 24 Hours of Le Mans, Audi entered a two-car team in the inaugural Intercontinental Le Mans Cup (ILMC). The three-race championship kicked off at Silverstone and also included Petit Le Mans in the United States and a race in Zhuhai, China. Peugeot had clearly rectified their problems and showed excellent form in all three races. Especially at Silverstone Audi struggled and even saw one of the R15s retire very early in the race with a drivetrain failure. The German team had to settle for a second at Petit Le Mans and Zhuhai, and a third place finish at Silversone.

The Audi R15 plus TDI's victory in the most important race of the year is what will be remembered of the 2010 season and fortunately for Audi, brand new regulations will come into effect in 2011. The all important win will no doubt have helped the top brass of VAG to continue the endurance racing program with the brand new R18 TDI. This will be the first fixed-head Audi sports racer since the R8C used in 1999. Ahead of the new machine's debut the R15 will make one final appearance in the season opening Sebring 12 Hours. The biggest point proven by the innovative Audi R15 is that the age-old adage 'to finish first, you first have to finish' still applies to modern-day endurance races.

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  Article Image gallery (80) Specifications