The R15 TDI succeeds the R10 TDI, retaining the turbocharged diesel concept but replacing the R10's V12 with a smaller V10 engine. The smaller unit is positioned further toward the centre of the car than in the R10, producing a more neutral weight balance and improved cornering agility. The engine displaces 5.5 litres (336 cu in) and produces over 440 kW (590 bhp / 600 PS) and 1,050 N⋅m (774 lbf⋅ft) of torque. The R15 was the first Audi sports prototype to use a lithium-ion battery. It also introduced LED headlights and an LED rear-light system mounted on the rear wing endplate.
The R15 was first tested in December 2008 and debuted on 21 March 2009 at the 12 Hours of Sebring, winning the race and setting a new race record. Three R15s then ran at the 2009 24 Hours of Le Mans under Joest Racing. Peugeot, with its 908 HDi FAP, took the top two places, ending Audi's five-win streak at Le Mans stretching back to 2004. The No. 3 R15 ran off at Indianapolis Corner early and eventually finished 17th; the No. 2, driven by Luhr, crashed and retired; the No. 1 lost a lap to the leading Peugeot during the evening and dropped a further seven laps due to technical issues before recovering to finish third. During the pre-race week, Peugeot had protested the R15 on the grounds that its bodywork was designed solely to generate downforce in violation of regulations; the ACO rejected the protest after the Wednesday free practice session. Audi did not defend its American Le Mans Series or Le Mans Series titles with the R15.
At the 2009 Petit Le Mans at Road Atlanta, two R15s led for approximately 90% of the race before a late spin during a rain-soaked final caution period handed victory to a Peugeot 908 HDi FAP. It was Audi's first loss at Petit Le Mans since its initial attempt there in 2000.
In response to the 2009 Le Mans and Petit Le Mans defeats, Audi updated the car for 2010 as the R15 Plus. The 2010 regulations reduced diesel LMP1 air restrictor size and turbocharger boost pressure, but Audi's engineering team, led by Ulrich Baretzky, matched the 2009 engine's power output. Aerodynamic changes included redesigning the frontal area to expose the raw crash structures, lowering the front fenders to reduce drag, and abandoning the air-through-the-car concept in favour of a more conventional configuration. The air channel exiting to the side of the car was also redesigned. The fuel tank and cooling system were improved.
The R15 Plus won the 2010 8 Hours of Le Castellet by five laps over second-placed Aston Martin, with the Oreca Peugeot entry finishing eight laps down after air jack failure; Audi ultimately finished ten laps clear of Peugeot. Three cars entered the Spa 1000 km, finishing third, fifth, and twelfth; Audi used that race as a setup exercise for Le Mans.
At the 2010 24 Hours of Le Mans, Peugeot led for much of the race and was faster in outright pace, but three of the four Peugeot cars retired with connecting rod failures towards the end, and a fourth suffered early suspension failure. The three R15 Plus cars finished 1-2-3: No. 9 first (driven by Mike Rockenfeller, Timo Bernhard, and Romain Dumas), No. 8 second, No. 7 third. The winning car completed 397 laps and covered 5,410.7 km (3,362.1 mi), setting a new distance record that surpassed the previous record of 5,335.313 km set in the 1971 race by Helmut Marko and Gijs van Lennep.
Post-Le Mans, Audi did not win any of the remaining 2010 races, losing all three to the Peugeot 908. At the Silverstone 1000 km, the No. 7 crashed and retired; the No. 8 finished third. At Petit Le Mans, both entries lost to a Peugeot 1-2. At the Zhuhai 1000 km — the R15's final race of 2010 — both Audis led until controversial Peugeot teamwork allowed the No. 2 908 to emerge from the pits two seconds ahead after a safety car period; the race ended with the Peugeot winning by four seconds. Audi did not win the LMP1 Le Mans Series team championship or the ILMC LMP1 championship.
The R15 made one final start at the 2011 12 Hours of Sebring, running in an upgraded R15++ configuration while the successor Audi R18 was still under development. The No. 1 car suffered two consecutive tyre punctures and rear bodywork damage caused by Mike Rockenfeller, then served a pitlane speeding penalty, finishing fifth overall. The No. 2 ran at the front and exchanged the lead with the Peugeot until a Peugeot shunt at turn 17 put Capello out with a suspension failure; the No. 2 finished fourth overall, five laps behind the winning Oreca Peugeot.
Audi developed the closed-top R18 to replace the R15 ahead of revised 2011 regulations. Wolfgang Ullrich cited favourable pitstop regulation changes and aerodynamic efficiency as reasons for adopting a closed-cockpit design. The R18 was Audi's first coupe since the Audi R8C of 1999, though the Bentley Speed 8, which won in 2003 with an Audi-developed engine, was also a closed-cockpit car.
This article is based solely on the supplied corpus. No external sources were consulted; claims that could not be substantiated against the corpus were omitted under the drop-the-claim rule.
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