The production design was frozen in late 2003, for a late 2005 start of production. Prototypes went into testing in 2004, with development concluding in the first half of 2005. It introduced the world's only series production passenger car V12 TDI diesel engine. While the Q7 has been the flagship SUV in Audi's product portfolio, a top-of-the-line coupé model, called the Audi Q8, was released for sale in 2018. It debuted in its concept form at the 2017 Detroit auto show.