[J DAWG]

You can't... You can only "guesstimate".
Here is a simple calculator to help...
http://www.dsm.org/tools/calchp.htm
Trapping 145 would be APPROXIMATELY 850 rwhp.
Peter

the day before I ran a 11.38 at 125.6 I dyno'd 503/535(I know the car is faster, but the driver sucked that day).

this said - Using the ET method, I come up with 483 horsepower
Using the Speed method, I come up with 557 horsepower


like you say it is just a guestimate, but interesting nonetheless.


ps - I got the same #'s from both sites.

 

[J DAWG]

Then here is my question, I dynoed at Larry's with a 391RWHP and 450 RWTQ(way disappointedissed, but using the calculator on this web site, I come up with 433RWHP (ET method) and 462RWHP (speed method). Why are these numbers so off. I believed my HP was going to be about 420 on the dyno. By looking at my ET and speed (11.8 at 118/images/graemlins/drive) during my runs I am no way 391HP, I should be in the 420 range. Any ideas?

You definetly have more than 391. My car with 426 rwhp was running 11.7 to 11.8 at 118, so I say you are right on the money at 420 or so.