Knowing that air resistance is a geometric progression, to be able to achieve 400 km/h + instead of 360km/h (as per Enzo example), you need A LOT more power *. As such, this 'invisible power' gives a lot of advantage in acceleration as well....
Anyway, the first time I saw that stock SL55AMG does 360+ kph or E60 M5 - 350+, I was like 'wtf'..this is waaay off. Crazy.
* In my estimated guess, with Enzo body aerodynamics, you would need 1200+ hp or more instead of 600hp. That's how much of a boost this bug delivers 
Also I think the point of miscalculation happens somewhere around 160-180km/h and upwards.. And above 220-230 you really start to feel the difference (between GT5 / Real Life and GT6)
Last edited: Nov 24, 2014