The Audi R8R was a Le Mans Prototype built by Audi for the 1999 24 Hours of Le Mans, and a predecessor to the dominant Audi R8 which debuted in 2000. It was raced alongside the British built closed-cockpit Audi R8C.
The R8R project began in 1997, when Audi began research into entering the 24 Hours of Le Mans. The first prototype was displayed in 1998, showing an open cockpit car which featured many Audi styling cues, yet lacked some of the practical necessities for sports car racing. The car, designed by Tony Southgate and built by Dallara, featured an Audi 3.6 litre twin-turbo V8 engine. Styling features included a large group of aerodynamic vents in the nose, as well as high sidepods which featured NACA ducts on their tops to feed the turbochargers. A large vent on the side also allowed air out from the front wheel well.
By the car's debut at the 12 Hours of Sebring, the aerodynamics were evolved. A longer tail was prominent, with the wheel arches more subtly curved into the side pods, instead of an abrupt hard-edge design. The front end was also lower, and featured more aerodynamic styling over the original stylized prototype.
However, following Sebring, further testing was done on the R8R in order to better improve its overall speed in preparation for Le Mans. The front bodywork was further evolved, with a wider and more curved sidepod being used. The NACA ducts were also replaced with a vertical air inlet coming out of the side fender. The tail was also shortened, and aerodynamic elements were added to the styling of the sidepods.
Only five R8Rs would be built total. #204 and #205 would run Sebring only in 1999, while #307 and #308 would run Le Mans. #306 would be added in 2000 to compete in the American Le Mans Series. Lessons learned from the R8R would be later evolved into the R8 for 2000.
Source: Wikipedia, 2011