1/4 miling would be too unscientific. There are too many variables. Drive a car down the strip get a 15.0. Lighten and balance it and get a 14.4.
But was it the lightening and balancing or:
Track temp
Tyre pressures
Air temp
Start
Wind speed
Track condition
Driver skill (maybe you were more switched on this time)
Oil level
Fuel level
Oil type
etc etc etc