If someone asked me to name Audi’s most successful race cars 20 years ago, my answer would’ve been simple: the Auto Unions of the 1930s and the Quattro rally car. Come 2015 and things are a bit more complicated, as Audi has become a dominant force in the endurance racing scene since 1999. It all started with the R8R and the R8 LMP, before Audi switched to diesel power with the R10 TDI and the R15 TDI. In 2011, the Germans introduced the R18, also motivated by a turbodiesel engine, but this time around paired to an electric motor. The R18 alone won 15 major endurance events in 2014,including four 24 Hours of Le Mans races, taking Audi’s Le Mans tally to 13 and making it the second-most successful manufacturer after Porsche. With the 2015 World Endurance Championship right around the corner, Audi is launching a revised version of the R18 that aims to take the nameplate’s success to a new level.