Quote:
Originally Posted by Glen Peciek
There are some significant differences between a drag strip and how the vBox calculates things. The drag strip has a 1' roll out, and the trap speeds are all an average of two points. I believe the 1/8 mile trap speed is the average of the speed at 600ft and 660ft, and the 1/4 mile trap speed is the average of 1256ft and 1320ft. So the vBox ET will always match the time slip, but the trap speed on the vBox will always show higher.
It is possible to write a program to read the vBox files and apply the NHRA rules to the results. Such a program does exist. When you use it, the vBox trap speed will usually match the timeslip within a few hundredths of a mile per hour.
Since there is some question about Sac's timing lights these days, it would be interesting to use such a program to scan the vBox files and see how closely they match Sac results.
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I have run dozens and dozens of track slip/vbox comparisons. Yes, in theory the Vbox should always read a little faster in the 1/4 trap than the timeslip, as the 1/4 speed is more the true speed than the speed averaged through a greater distance (the track timing lights). But the fact of the matter is, some tracks actually read faster than the Vbox, and some are close to the same. The other day in AZ a guy in a 335i ran a 10.2x at 117 mph or something like that. Its too bad he didn't have a vbox to see what he actually ran.
Once I figure out what the track/vbox trap speed differential is, I will know 99% of the time, almost exactly what my timeslip is going to read before I receive it.