Is it just me, or does the HP/ET calculator assume a bunch of perfect scenarios. Track prep, soft launches, spinning, slipping lockup, incorrect torque etc etc all make for a slower MPH/ET when you are trying to achieve perfect. Would it not be better to refer to the calculator as a reference guide to what the equivalent power you put down on that pass versus "your only making this much according to 2 input variables..."
With that being said, i agree correction factors should not be used. its all about what you put down that day at that time to the tires.