AUDI AG is the world’s first automobile manufacturer to develop a “second” generation diesel racing sports car. Audi further improved the R15 TDI diesel race car for the 2010 season with the primary objective of securing victory at Le Mans.
“As far as Audi is concerned, the LMP1 is better than Formula 1 vehicles because this motorsport category involves technologies and developments that are relevant to series production,” explains Head of Audi Motorsport Dr. Wolfgang Ullrich. “The most important thing at Le Mans is efficiency. That’s precisely what is in greatest demand in production vehicles these days, and this is also one of Audi’s main strengths.”
Efficiency – especially in relation to aerodynamics – was therefore a key focal point when the R15 TDI was being further developed. “This year’s Le Mans regulations prescribe smaller air restrictors and lower manifold pressure,” says Audi Sport’s Head of Technology, Dr. Martin Mühlmeier. “As the regulations resulted in reduced engine performance, we endeavored to make the aerodynamics even more efficient and improve the drag coefficient and downforce values.
The entire shape of the R15 TDI bodywork has been reworked with maximum efficiency in mind, as has the modiﬁ ed cooling and tank system. The V10 TDI engine has been optimized to cater for the smaller air restrictors and he reduced manifold pressure. The two air intakes have been reduced in size by just under two percent, from 37.9 to 37.5 millimeters. The manifold pressure, which is a key feature of turbo engines, had to be changed from 2.75 to 2.59 bar, which is a sizable reduction of 5.8 percent. “We aimed to keep the loss of power to a bare minimum, in spite of the curtailments introduced by the new regulations,” explains Audi Sport’s Head of Eingine Development, Ulrich Baretzky. “And we achieved this with a lot of work on details.” The 5.5-liter engine still generates more than 440 kW of power and it goes without saying that two diesel particulate ﬁ lters clean the exhaust fumes of the Audi R15 TDI. The torque, which is still as big as ever, is passed on to the rear wheels by a pneumatically operated ﬁve-speed gearbox.
“There were about 20 important points on our speciﬁ cation sheet for the ‘R15 plus’ after Le Mans 2009,” says Dr. Martin Mühlmeier. “Most of them concerned issues of efficiency and reliability, but there were also details such as a request from the drivers for better night-time illumination of the racetracks. And we met this request with a new headlamp concept.”
The new generation of the Audi R15 TDI is also equipped with a highly efficient electrical system. A lithium-ion battery and LED headlamps deliver an excellent light yield without adding excessive weight to the vehicle.
The 2010 prototype of the Audi R15 TDI was ﬁ rst put through its paces at the Audi proving ground in Neustadt at the beginning of March, before being ﬂ own out to the USA to undergo testing, especially in relation to its aerodynamics. There then followed a ﬁ ve-day endurance test at Sebring, in which the vehicle completed approximately 5,500 kilometers without any noteworthy technical problems.