I dont have access to a speed trap, best thing i can do is bring the GPS in my real car and compare the speed in a video.
I can try to have a better reading on the radar but it is very dangerous.
Heres a previous video when we crashed it, it was still accelerating, but loosed control.
The radar update speed faster than the GPS as some may know, we got 84mph on the radar and 81.9mph on GPS.
(from 5 minutes 30)
http://www.youtube.com/watch?v=-i0ludmC4fA