Audi has put the latest version of its new diesel race car R18 to test for the first time in the U.S.

The 'Evolution 2' Audi R18, which will appear in the 24 Hours of Le Mans, is the result of the findings of previous test drives and wind tunnel testing, with a particular focus on improved aerodynamic efficiency and cooling of the interior of its V6 TDI engine.

The car clocked up its first test kilometers on a proving ground in Florida last week, as the 12 Hours of Sebring were held.

Two 'Evolution 2' R18 vehicles were put to the test during the four days of testing in Sebring, together with an R15 TDI as a reference vehicle. Ten Audi racing drivers were involved in testing the three vehicles, clocking up thousands of test kilometers to generate important findings relating to vehicle setup, aerodynamics, tires, cooling, and reliability.

The Audi R18 will make its next appearance on the famous racetrack in Le Mans, when the definitive design of the vehicle for the 24 Hours of Le Mans 2011 will be unveiled at the official testing day on April 24.

The R18 is scheduled to compete for the first time in the 6-hour race in Spa-Francorchamps on May 7, 2011.