buddy chill out I'm not here to start any back and forth bantering on this site. I was just wondering how you would figure out your actual calculated speed without 'guess-estimating.' I thought maybe you were using a GPS or something.I think 99% of the people on here can figure this out, but I guess I will answer it for you since you seem to be a special case.
If you run the car up to the limiter and it shuts down, then you flip the switch and the car starts gaining speed again, you know you are going faster.
You can also watch the tach right when it shuts down, and note the rpm, then watch it rev much higher when the switch is flipped.