I bought a used Performaire Eclipse weather station and predictor last year,so I'm not sure if the current TAG units are like the Performaire or not I have kept race logs for a long time, I use to have and used one of the first generation weather stations and predictors, that one went bad when the memory battery ran out That company has gone out of business also My point is your TAG needs current weather infomation to predict accurately, like Mike has already said, it doesn't do any good to enter it at home after the race I erase all the runs in the unit I have if I make a mechanical change to the car like changing carbs,jets, tires or what ever I select the multiple runs for predicting and then use that information, along with a grain of salt, to decide what I'm going to dial Don't use last weeks information to dial in for todays races Good luck, don't get overwhelmed with to much information, remember the KISS principals and use that