1999 Audi R8C

Images courtesy and copyright Audi AG
Text copyright Michael J. Fuller
Audi R8CIn this view you can see the effects of the frontal area reduction program.  We understand that only the one front fender configuration, where the fender was open on the inner face to allow for a narrower fender, and was, "cribbed from Toyota," as designer Peter Elleray admits, was ever tried in the wind tunnel.  In hind sight, while it did add downforce,  the Toyota solution also added drag and didn't have any effect on frontal area (given the rear wheel masking it in front elevation).

In this view we can also see the cut-out in the roof of the cockpit (the "buttification" as one wag put it).  According to Race Car Engineering, the roof humps were designed for driver helmet clearance, the space between the humps being below the minimum legal height, the peaks being just at minimum height, all to help improve airflow to the rear wing.
Audi R8CNote the small horizontal strake at the rear of the longtail.  It's net effect was to increase the rear diffuser width to the max car width.  It's been theorized that the strakes also created a vortex that helped wake infill as well as produces a small amount of downforce on the surface.
ęCopyright 2010, Michael J. Fuller