It's not linear though, I think? I think it would be exponential as wind resistance would increase by greater amounts at higher speeds. Or I could be totally wrong?
wind resistancw would affect the power needed to reach top speed but the RPM to KPH theory can work... given that if your RPM is at a certain number, that is drivng the drive train all the way to the wheels and the road. The only time when this would not be true is if you break traction, or you have loss of power thorugh the drive train (slipping clutch)
Easy enough to use a gear calculator if you want to know what speed you were going at certain rpm. Eg http://www.f-body.org/gears/ Axle ratio (TT): 3.69 1st:3.214 2nd:1.925 3rd:1.302 4th:1.000 5th:0.752 6800rpm top speed limit: 180mph 7000rpm : 186mph 7200: 191mph etc.
top speed in my n/a z32 was around 235km/h at about 6am on a straight piece of highway on the way to qld a few years back.
mine was up to about 160 tops, but i wast even driving, i dont have any points left and am about to gat a 3 months suspension , Was accelerating into an 80 zone, but because i was doing 80 before the sign... i got done 82 ina 60 zone.... 250 and 4 points, I even heard other cops that i know that say the guy that gave me the ticket is a wanker... There was another car right up my ass that pulled over as well... But i was told by the copper he wasnt speeding.. only me, Because that guy obviously didnt have p plates........... Bitch Over...