Basically, You use the amount of time between the cars finish line times, X the MPH of the second car, X 1.47, which changes mph to fps.
Having an opponents incrementals is absolute gold!! Knowing 1000'-1320' split times helps you understand the closing rates. What the drivers sees in that emotionally charged moment, as his adrenaline is spiked...and what the numbers spell out are often 2 different stories!! And the numbers don't lie!!!