Quote Originally Posted by J57ltr View Post
How? Horsepower is a calculation not a measurable quantity as I understand the formulas and how Horsepower is derived. Not arguing just I don't understand this.

the only way I can see this happen is if the car spins the tires on the dyno.

Jeff
Thats pretty much it, real-world variation. There are different kinds of dynos and the info is best used in comparison to other tests run on that same dyno setup. Look at enough readouts and you'll see that the intersection is never far from 5252 but rarely falls exactly on it. Drive-on dyno numbers must be less consistent than flywheel due to all the added machinery between the powerplant and the dyno. Its not an exact science, but the math is.