That's why I said Before and After times slips. I was implying that they be from the same car with the same driver. I have found that these cars run VERY consistent at the track, so even an average driver should be able to consistently reproduce the same times...

I think there is MORE variation from one dyno to another. I've dynoed cars on three separate Dynos with the same mods and gotten three vary different readings. There is also a broad range of options for viewing dyno charts. Peak numbers are all over the place depending of if its SAE corrected, takes into account humidity, temperature, Altitude etc.. Then there is the smoothing curve. Smoothing 0 will show higher peak numbers, with no smoothing which is not very accurate. Smoothing 5 takes out all the peaks and valleys in the chart to show a "true" power curve. A lot of dyno racers will quote "raw" uncorrected and smoothing 0 charts to say they made more peak power than they accurately do.

Mustang Dynos, Dynojets, Dynapacks all read very different numbers with the same car hooked to them. Therefore, in my mind, unless I'm there to interpret the dyno chart in person, it doesn't mean that much because you don't know how it was read, set up or what type of dyno it is. A dyno is great for tuning a car for the track, but only the track gives you the full story...

To me, quoting dyno numbers is the same thing as quoting numbers out of a magazine... Verifiable time slips that show a progression of mods tell a much better storya dn show a much more accurate tale of what is really going on while testing ONE car.