Le Mans debut for new Audi R15 TDI

Logical lightweight construction, downsizing, efficiency and the best possible aerodynamics – the same subjects which currently occupy the brains of the automobile industry development departments are also key elements in the 24 Hours of Le Mans held for the 77th time on the weekend of June 13/14.

In the world’s most famous endurance race it is, in addition to speed, also more a question of reliability and efficiency – and to set trends afterwards. Audi has used Le Mans since 1999 to test technical innovations under racing conditions and has, in the process, repeatedly set milestones thanks to its technology leadership. In this way, the Audi R8 successfully introduced gasoline direct-injection TFSI, with the Audi R10 TDI in 2006 a diesel powered car won for the first time in the history of the race.

The Audi R8 and Audi R10 TDI have one thing in common: Both were victorious on their Le Mans débuts. Audi Sport Team Joest now aims to continue this phenomenal trend with the new Audi R15 TDI in Audi’s 100th anniversary year. A ninth victory – with only eleven participations – would see Audi draw level with Ferrari in the French endurance classic’s all-time winners list. Only Porsche has achieved more victories in its long Le Mans history.

The R15 TDI is packed with technical innovations. Among them a more compact, more efficient V10 TDI engine, logical lightweight construction, a totally new aerodynamic concept never before seen on a Le Mans sportscar and a novel vehicle power supply system using for the first time a lithium ion battery as used in hybrid vehicles of the next generation. It is lighter than a conventional battery and instead of supplying the more common twelve volts usually found in production cars, it supplies 15.2 volts. As a result of the higher power, electric consumers such as the starter motor can be designed to be smaller and lighter and thus increase the efficiency.

Logical lightweight design and construction

In general the Audi R15 TDI was trimmed logically for lightweight construction. The minimum weight of 900 kilograms originally stipulated by the regulations was significantly undercut through complex and intricate measures in order to facilitate the best possible weight distribution. That the Automobile Club de l’Ouest (ACO) ordered the minimum weight to be increased by 30 kilograms for diesel cars at short notice before the race hit the Audi Sport technicians hard. As a result, the R15 TDI was robbed of one decisive advantage.

To fit the additional 30 kilograms in the aerodynamically refined car several R15 TDI components had to be modified and their durability checked in extra endurance tests. The green light for the final version was thus only given following a successful 30-hour test at Le Castellet at the end of May – less than three weeks before the race. A few days later, on May 29, the roll-out was made at a test track close to Ingolstadt for the three newly built-up race cars with the chassis numbers 104 (start number "1"), 105 (start number "2") and 101 (start number "3").

The new Audi R15 TDI demonstrated its potential in March on its victorious race début at Sebring (USA). Many details have been optimized on the diesel racing sportscar for Le Mans since then. Improved cockpit cooling also numbers among the modifications.

Aerodynamic Cd optimized

Furthermore, an aerodynamic version designed for efficiency is used for the first time at Le Mans. While the R15 TDI still races with maximum downforce, a more favourable Cd value for the long straights at Le Mans is of prime importance. The R15 TDI nevertheless generates more downforce than its predecessor model the R10 TDI thanks to its innovative aerodynamic concept incorporating the uncompromising implementation of air-flow through the car.

Key factor tire wear

A very decisive factor during the 77th running of the 24 Hours of Le Mans will be the lowest possible tire wear. Since only two, instead of the previously allowed four mechanics, can change tires during pit stops the standing time in the pit almost doubles. Therefore it will depend more than ever on being able to drive for as long as possible on the same set of tires without losing too much performance.

The six-hour free practice session on Wednesday evening and Thursday evening’s four-hour qualifying session are therefore of particular importance. Because there was no additional test day for the first time before the race, Audi Sport Team Joest will use both days efficiently to find the optimum car set-up and to find the best tire choice for the race. Indeed, grid positions in a 24-hour race are of secondary importance for the final result.

Last year’s winners Dindo Capello (Italy), Tom Kristensen (Denmark) and Allan McNish (Scotland) drive the Audi R15 TDI with car number "1". The three Germans Lucas Luhr, Mike Rockenfeller and Marco Werner share car number "2". Sharing driving duties in the R15 TDI with car number "3" are Timo Bernhard (Germany) and the two Frenchmen Romain Dumas and Alexandre Prémat.

As well as by their car numbers, the three Audi R15 TDI can be distinguished by the different additional colours yellow (car #1) red (car #2) and black (car #3).

Some of the team has been in Le Mans since Wednesday (June 3). The three Audi R15 TDI cars arrived in the paddock on Friday. The public technical scrutineering in the Le Mans town centre is staged on Monday (June 8), practice begins on Wednesday evening. The start is scheduled on Saturday (June 13) at 3:00 p.m. Eurosport broadcasts almost the entire race "live".