BTW : To me this shows also how misleading these test times are . They are done in ideal conditions, with professional drivers, and with an empty track .  At the end, the differences between an RS an R8 + or TTS is half a second . 

Driving behind a car that is thematically half a second slower then your in hands of professional , makes it impossible to over take it . You get stuck behind . Unless you are willing to put your car and the other's car at a very high risk of crashing .  What you might gain in some parts of a track ( like slower curves with the RS ) you loose it instantly when there is a straight because of the extra power of the R8 . ..... and so on .

So, in real life, these differences are minor .

Another example :  on the long straight 1.1 km .  The RS is exactly the same speed a GT3 . No difference .  Difference gets only once you hit the big right curb because of greater downforce . 

Another example :  With 2 fairly good drivers, a Turbo S is also faster over an entire lap then an RS . Because of the extra pulling power out of the curves and the extra speed on the straights . ( taking into consideration driving behind each other and that means leaving a safety margin , which you always will in normale real world driving events ) 


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 964 Carrera 4 --  997.2 C2S , -20mm --  991 GT3 RS