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how to figure 1/4 times w/hp #'s

J

joncsfreak

New CEG'er
Joined
Sep 12, 2007
Messages
25
Location
Carson City, NV
Well, What I would like to know is if anyone knows a way of figuring a 1/4 mile time by whp?

of a contour/mystique?



also, Does any one know of a place that sells the tool you put on your dash and it gives 0-60 times, 1/4 mile, and 1/8 mile read outs?
 
I'm sure you can come up with an estimate by looking at other's data, but being that there are so many factors such as weight, traction, reaction, etc, you really can't get a near exact measurement without actually running the track. You can't really calculate the 1/4 mile from a measurement of hp or even torque for one specific reason: the car makes that hp or torque at a given RPM, and unless by some act of God you were able to hold that exact RPM the entire length from start to finish then simple physics could be used to get an idea (again, this is under the ideal conditions of a single target RPM being held AND assuming there is no loss of traction or wind resistance) of where you could be in a 1/4 mile. Now if your really want to get into it you could figure out the RPM range you would be in for the majority of the run and take the hp and torque readings from a number of RPM's within that range and average them together. You could then use the averages hp and the average torque to get a ROUGH estimate of where you COULD be in a 1/4 mile. In all honesty, the numbers you come up with would probably be way off.

To answer your second question, there are a number of tools. Check this thread for two of them: http://contour.org/ceg-vb/showthread.php?t=28378
 
i cant believe i never saw this thread before. there is actually 2 equations that are used to calculate ET and MPH for a 1/4 mile run based on HP and weight. i dont have them with me at the moment as they are stored in my calculator at home but i will post them tonight. although not perfect, the calculations are actually fairly accurate.
 
striker2 said:
i cant believe i never saw this thread before. there is actually 2 equations that are used to calculate ET and MPH for a 1/4 mile run based on HP and weight. i dont have them with me at the moment as they are stored in my calculator at home but i will post them tonight. although not perfect, the calculations are actually fairly accurate.
Click to expand...

Even taking traction and among other things the DRIVER into account????

Theoretically I think you could get an estimate but I just don't see how you could get an accurate estimate.
 
Wow I take that back. They must of taken a lot into account here but I found this calculator and using stock weight and horsepower I was able to come up with the times people seem to be making around here.

http://robrobinette.com/et.htm


I need to contact them and find out what kind of math is going on there!

EDIT

Although it seems fairly accurate for lower numbers, when you plug in say 400 whp, it returns a time in the 11's. Obviously those here with 400whp are not making 11's due to extreme traction issues. This may be more accurate for a rwd vehicle.
 
Last edited:
xtascox said:
Even taking traction and among other things the DRIVER into account????

Theoretically I think you could get an estimate but I just don't see how you could get an accurate estimate.
Click to expand...
it assumes you have traction and a good driver obviously. IIRC it said i should have been running ~16.3 with 125WHP and 2800lbs. that happens to be almost dead on. i was actually running about 16.4-5.

ill find out just how accurate it is at SZ as i know it says i should be running a 13.6 with 220WHP and 2800lbs. like you said, it is just an estimate but it has been very close on every one i have tested it on (i have actually asked people for their hp and weight numbers, calculated it and then asked what they were actually running and it was pretty close every time)


Edit: Ill post the equations tonight. and yes they arent running 11s cause they cant get traction till 3rd - 4th gear.
 
I didn't realize it was javascript:troutslap:

Using WHP:
((weight / hp)^(1/3))*5.825

Using Flywheel HP:
((weight / (hp*.854)) ^ (1/3)) * 5.825

Now what I really want to see is where these equations were derived from!
 
xtascox said:
I didn't realize it was javascript:troutslap:

Using WHP:
((weight / hp)^(1/3))*5.825

Using Flywheel HP:
((weight / (hp*.854)) ^ (1/3)) * 5.825

Now what I really want to see is where these equations were derived from!
Click to expand...
ET:
((Weight /WHP)^(1/3))*5.825

MPH:
((WHP/Weight)^(1/3))*243


those are the equations i have. im not sure who or how they figured it out but it is a fairly accurate estimate.
 
I'm going to see if I can modify the equations so that they remain accurate for at least our cars at higher power ranges. Shouldn't be too hard.
 
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