Why don't you give us the fact that these cars you wrote have less weight than C7? F40 1200 kgs, P959 1150 kgs and Diablo is more powerful to overcome its added weight. 👍
Play with
this, set the rolling resistance and drag coefficient to zero - notice that top speed is only limited by
drag forces. Notice also that, with sensible drag figures re-instated, mass only affects the rolling resistance. In effect, changing the mass only alters the split of power given to overcoming rolling resistance and that overcoming aero drag. That varying proportion gives rise to the variance of the transition point in the power requirement vs. speed graph from being straight (rolling resistance dominated) to curved (aero dominated).
Some interesting points: with the defaults on that calculator, you only need 17 bhp to get to 60 mph. But, 17 bhp enables a 0 - 60 time of about 50 seconds in a drag-less system, much more with drag (well, infinitely more, actually - you need more than 17 bhp to achieve 60 mph at all). 120 mph requires 90 bhp and takes 40 seconds without drag.
Drag is the key issue with top speed, and rolling resistance (and hence mass) is usually secondary to aero - all that's left is a requirement to add kinetic energy to the car at a certain rate, which comes from how much larger the accelerative force is over the drag force. Thus, as long as the driving force is even only slightly larger than the drag, the car will keep accelerating
indefinitely (see Newton's laws of motion) - mass does not in itself limit top speed, only really acceleration.
You could exploit this in one of the past Daytona seasonals. You found the heaviest 200 bhp car you could and, although it might have been a challenge to stay in the slipstream at the start, once up to speed, it'd have no problem with winning just the same as if it were an Elise, and your PP bonus would have been through the roof!
👍, the new Blue Devil. 
