I've used mine at the track probably 25-30 times, the furthest it has been off was .06 seconds. It has read slower all but one time, and that one time I think it read .01 or .02 faster than my time slip.
I did have a revelation while sitting in the staging lines the other night at the track that I never thought about before. If I am correct, that would mean dragy is even more accurate than I had believed.
Dragy starts as soon as your car moves. At the track, your time isn't started until you cross the first lasers, and depending on whether you shallow stage or deep stage, I'm sure that could account for how far off the dragy times are vs the time slip.
Next trip to the track I will try to deep stage a couple times and see if it brings the gap down a hundredth or two. Mine has been pretty consistently always .05 or .06 higher than the timeslip.
