Originally Posted by Chuck33079

Some of those do have an effect. Your post before the one I quoted above was a bunch of unlikely and extreme examples, and not really worth much of a response.

You are correct, some of the things you mentioned do have an effect on traps to some degree. Traction/wheelhop is really to only one to be concerned with. Gas quality, temp and altitude would effect dyno numbers to the same degree as trap speeds. Your last two are asinine.

You're correct in pointing out that trap speed is not an absolute, and it can be affected by outside factors. So can dyno numbers. Dynos can be made to show you pretty much whatever number you want. The only way to get an absolutely correct hp reading would be an engine dyno in a controlled environment. Any other method has drawbacks.

Trap speed is very commonly used to calculate HP. The formula for calculating hp from trap speeds is:
hp = (mph / 215.39)3.3135 x weight (lbs)

This page has a pretty good breakdown of the math involved, if you're curious. Shamelessly stolen from a 300GT/Stealth site. Stealth 316 - Formulas for 1/4 mile ET & mph vs. hp & wgt