Fiber and BB are both correct in there posts. But BB, I have to say that Fiber is probably more accurate than yours.

But don't get me wrong here BB, yours works much easier and with much, much, much, much less explanations as Fibers! :lol:
I raced for 20 years, and one of my deals was a 500 CI Pro Stock Style Motor, Pontiac/Brodex, BME, KRYPTONITE, Comp. Cams, all the best stuff money could buy at the time, which happened to be "every year". :bang: The most sophisticated piece of engineering known to man within the "normally aspirated" engine world, also the last thing that can sometimes be put on a Dyno without "breaking it" or without taking it out of calibration when you exceed it limitations!
Every time I went to the dyno, I had to purchase a minimum of 5 "NEW" input shafts for the dyno, and pay upfront for the required recalibration afterwards, with no questions ask! I BROKE A LOT OF THEM! :lol: And they tried to BREAK ME TOO! :lol: We'd dyno tested once to twice a year to compare new changes we had made.
And Fiber is very correct as to what he is saying, it's "ALL" relative to the operator! Inclusively "Comparisons" by shops as well!
Let me just shine a little light out here for you guys to chew on.
1) Owners want to dyno to see how much HP & Torque they've got, right?...More is Better, Right?
2) If the mechanic operating the dyno can give you better numbers by making a small or big change, you're going to want it, right?
3) Who make money on the changes?
4) Who makes money if they can show you better numbers?
5) Who is going to make money with no changes and better numbers?

.... GET IT!...It's somewhat adjustable in the "programing" of all manufactures of dynos!
There are those that will take advantage of you, "not all", but some! It's in the best interest of their pockets! $$$$
So don't believe everything you hear or even see sometimes.
My best advise here is; "Be somewhat "Quietly Sceptical" until "PROOF" shows you otherwise!
"Horse Power Cost!...How Fast Can You AFFORD Too Go"!
Good Luck! :2thumbs: