Estimating HP from 1/4 m trap speed

[wrsbmw]

Since the HP rating seems so important to evaluating the effect of mods, I was looking for more ways to estimate horsepower than just the dyno. The reason I bought the Vbox was because I discovered that there is a fairly good history of estimating horsepower from 1/4m trap times, ET not so much because it is very traction dependent and related to the skill of the driver. Trap speed represents the ability of the car to accelerate in the 1/4 mile distance once it gains traction after the first 60 feet or so.

I found several links for estimating HP from 1/4 m data but I think the best one is here

http://www.stealth316.com/2-calc-hp-et-mph.htm

It has several different calculators and gives an explanation of the different methods used to estimate hp from the 1/4 m data.

According to the Hale Formula, my trap speed indicates 580hp. Interestingly, this estimate gives crank HP and not wheel HP because it includes/explains losses in the estimate. Other forumlae give my HP over 600 which is probably too high since the car is stock.

I am going to be using these formulas to evaluate the effectiveness of the mods when I get the car back and make some 1/4 mile runs.

[Tom C]

Originally Posted by wrsbmw

Since the HP rating seems so important to evaluating the effect of mods, I was looking for more ways to estimate horsepower than just the dyno. The reason I bought the Vbox was because I discovered that there is a fairly good history of estimating horsepower from 1/4m trap times, ET not so much because it is very traction dependent and related to the skill of the driver. Trap speed represents the ability of the car to accelerate in the 1/4 mile distance once it gains traction after the first 60 feet or so.

I found several links for estimating HP from 1/4 m data but I think the best one is here

http://www.stealth316.com/2-calc-hp-et-mph.htm

It has several different calculators and gives an explanation of the different methods used to estimate hp from the 1/4 m data.

According to the Hale Formula, my trap speed indicates 580hp. Interestingly, this estimate gives crank HP and not wheel HP because it includes/explains losses in the estimate. Other forumlae give my HP over 600 which is probably too high since the car is stock.

I am going to be using these formulas to evaluate the effectiveness of the mods when I get the car back and make some 1/4 mile runs.

The other caveat I would include is the impact of weather on the trap speed. You might use a DA calculator to try an equalize the impact of weather on the results. It too is a bit flawed as it will not take into account extreme conditions have on how the DME is reacting. For example in hot and humid weather, the DME could pull significant timing and reduce maximum boost pressure whereas the DA calculator will only be weather correcting the results.

Here are some tools I use from dragtimes:

http://www.dragtimes.com/drag-racing...tors-tools.php

[Northern X5M]

Like Tom said, trap speeds and DA.
I like the Drag Times DA Correction factors, it is a good method of standardizing geographic location and weather. Trap speeds are very consistent regardless of ET. ET's can fluctuate up to a second (extreme), where as Trap Speed may only fluctuate 0.5 MPH or less.