what is the formula for calculating hp from mph thru the 1320 traps (~96 mph) and weight (4320# (always take my daughter or wife))

Go here (http://www.prestage.com/Car+Math/ET+and+Horsepower+Calculators/HP+from+MPH+and+Weight/default.aspx). This is RWHP.

(.00426 x mph) x (.00426 x mph) x (.00426 x mph) x weight.

Originally posted by Pat Kelley:
Go here (http://www.prestage.com/Car+Math/ET+and+Horsepower+Calculators/HP+from+MPH+and+Weight/default.aspx). This is RWHP. =
Pat,
I must respectfully disagree with their formula for RWHP.
It will give you approximate flywheel HP
They are using a formula that calculates flywheel HP & calling it rear wheel HP.
I have emailed them a couple of times about this but apparently it is unimportant to them to correct it.
As an exaomple, according to their formula a 2350 lb Pro car would be making over 1500 rear wheel HP :eek:

I have posted this before but here it is again:
Here is a little formula that has been around since at least the 70's & was used by Chrysler Corp. in their drag racing program & written up in the American Journal of Physics in 1973
HP=(.00426*MPH)cubed * WGT
I add about 50 HP to the number because MPH is measured differently now than it was in the 70's.

So,,,,,,,.00426*97=.41322cubed=.07056*3400=240HP
Add 50 to be nice,,,290HP
I find this formula works pretty fair until you get into some of the very hi end cars like Pro Stock. I find with cars like these it will give you a higher HP number than you usually see, especially adding 50HP.

This formula might be old but I believe most of the laws of physics still apply,,,,,,unless of course you are using that "Good LA air" when you dyno :D :D

I was unaware there was a problem with Prestage's formula. They don't say it now but use to say it was RWHP.

Using my numbers 115 mph and 3400 lbs. I get, using the formula you posted, 399.76 hp. Prestage gives 404 hp. Pretty close. Adding 50 hp, 449.76 and 454 hp. This could be fwhp, I guess and sounds about right. Using the raw numbers and 20% DT loss, makes 499/504 hp. Which seems higher than I think the engine makes. BTW, I think Westech was build for magazine editors smile.gif .

BTW, how was mph measured differently? Were miles a different length or were hours longer or shorter? smile.gif . I know what you mean, the trap speeds were measured differently.

Rich,you need to go down the track with just yourself on board ;) smile.gif

email me sometime:

ccorwel@laticrete.com