The V12 had one last hurrah in sports car racing as the noughties drew to a close. Yet the powerplants that won the Le Mans 24 Hours four years on the trot from 2006 to 2009 weren’t ear-tingling screamers. Fans awaiting the arrival of a new breed of prototype were greeted by the rap, tap, tap of the front splitter on the track surface rather than a sonorous engine note. This was the era of the whispering turbodiesel.
Audi and Peugeot took up the challenge presented by the Automobile Club de l’Ouest when it opened up Le Mans and its associate series to diesels for 2004. Both opted for the V12 route for their turbodiesel LMP1 challengers in 2006 and ’07 respectively. The reason? Conservatism.
Ulrich Baretzky, Audi Sport’s long-time head of engines, admits that he “knew nothing about turbodiesels” when he and his team set out to exploit the rules. “The capacity limit was
5.5 litres and we were allowed 12 cylinders, so we went to the maximum: more cylinders meant less load on each. I was fighting my colleagues on the road car side who told me I had to do a cast-iron block otherwise the engine wouldn’t last. But I said to them I would never, ever do a cast-iron race engine.”
Peugeot’s engine was similar in architecture, save for a 100-degree vee angle, to the Audi’s 90. It contracted a specialist in diesel combustion who specified a certain cylinder bore, leading it down the same 12-pot route as its rival.
The Audi R10 TDI won on its debut at the Sebring 12 Hours in 2006 and followed it up with victory at Le Mans for Emanuele Pirro, Frank Biela and Marco Werner; and Peugeot won the opening two rounds of the 2007 Le Mans Series with its 908. When they met for the first time at Le Mans, the French claimed first blood in qualifying, but Audi made it two wins in a row with the same trio of drivers as 2006.
Peugeot made a big step for 2008, swapping from aluminium to steel pistons that gained it as much as 100bhp. A Herculean drive by Tom Kristensen, Allan McNish and Dindo Capello, the R10’s superior traction control and an overheating issue for the 908s allowed Audi to complete a hat-trick with its V12 turbodiesel.
In 2009, Peugeot notched up what stands as the last victory for a V12 at Le Mans. A switch to titanium conrods in ’10 proved its undoing and Audi’s R15-plus TDI with a V10 — and aluminium pistons — inherited the win.
What turned out to be the final battle of the turbodiesels was fought out in 2011. New rules had limited engine capacity to 3.7 litres, and Audi returned with a V6 and Peugeot with a V8.