Dürheimer had originally signed on as Audi's R&D boss in September 2012. Prior to that, he had served as the head for both Bentley and Bugatti, and was formerly the development chief at Porsche (where he is credited with helping get the original Cayenne into production, a move that ushered a new era of profitability for the company). Dürheimer moved to Audi following a management shakeup within the Volkswagen Group in mid-2012.
During his time at Bentley, Dürheimer spearheaded the brand's efforts to launch an SUV. But at Audi, he reportedly quickly put a stop to costly projects such as the R8 E-Tron and the rotary range-extender engine for the A1 E-Tron. Furthermore, Car and Driver reports that Dürheimer shuffled the reporting structure within the brand's design department, and that VW Group CEO Martin Winterkorn had apparently disagreed with him several times on the styling direction for the brand.
Also of note, Der Spiegel posits that Winterkorn strongly disapproved of Dürheimer's conservative E-mobility strategy, and that there was further tension between the two gentlemen on a personal level that could have led to this dismissal.
Dürheimer's future within the Volkswagen Group is unclear at this time, and his position at Audi will currently be filled by the Group's R&D chief, Ulrich Hackenberg.