For the first time since 1999, Audi will present a closed car at the start of the Le Mans 24 Hours (11-12 June). According to the German automaker, its aerodynamic efficiency is one of the strengths of the R18 TDI.

"I really liked the ‘open’ cars but there are beautiful ‘closed’ sports prototypes as well - and I think that the R18 TDI is a typical Audi making a very good visual impression." says Wolfgang Ullrich (Head of Audi Sport). However, the choice of the closed architecture was not dictated by aesthetic criteria.

Explanation: It is not only aerodynamic efficiency that plays a role in the decision for or against a ‘closed’ car. The sporting regulations developed in such a way over the years that one of the roadster’s decisive advantages - namely fast driver changes - was eradicated: changing tyres at Le Mans now takes considerably longer due to the fewer number of mechanics allowed to work simultaneously on the car. Therefore a fast driver change is no longer a decisive factor.

The wind tunnel continues to play a major role during the development of a Le Mans sports car. The relevance of CFD (Computational Fluid Dynamics) simulations was increased significantly. CFD allows engineers to simulate the air flow around and through the car. "While basic concepts and also complex detail tests are calculated, performance relevant dynamic running conditions can be evaluated in the model wind tunnel," explains Axel Löffler, Head of Chassis Development and Aerodynamics at Audi Sport.

The fin, stipulated by the regulations, which extends between the cockpit and rear wing and which should help to reduce speed in the event of a spin, had considerable influence on the design of the R18 TDI. "Integration of the new fin in the overall vehicle aerodynamics was the result of extensive analysis," says Axel Löffler. "To respect the safety aspects without creating losses in the overall efficiency required completely new approaches during development." (See photo)

And these efforts are paying off, as explained Dr. Wolfgang Ullrich: "Aerodynamics has always been one of Audi’s core skills. It speaks for itself that in spite of significantly reduced engine power we reach almost the same top speed and levels of downforce like last year with the R15 TDI."

Julien Hergault - According to the communique Audi Sport

Photo: Audi R15 "Plus" - Audi R18 ... Two very different concepts.