Time Vs RPM... could I pull a horsepower number out of that? (physics gurus needed)
05-23-2004, 09:55 PM
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Time Vs RPM... could I pull a horsepower number out of that? (physics gurus needed)
I got this software right now that analysis wideband logs.... you know I was thinking.
If I take the RPM, gear ratio, wheel size with the time. I should be able to get a horse power estimate correct?
Help me out with the formula all you physics gurus.
Nick
If I take the RPM, gear ratio, wheel size with the time. I should be able to get a horse power estimate correct?
Help me out with the formula all you physics gurus.
Nick
05-24-2004, 12:58 AM
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Re: Time Vs RPM... could I pull a horsepower number out of that? (Sinner)
You can figure horsepower if you know the (delta)rpm and the weight of your car. There are actually software where one connects an inductive pickup to a laptop (as a microphone), but I am not sure of the actual formula...I believe 1HP = 30,000 lb*ft/min...so, go figure 
05-24-2004, 04:46 AM
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It can be done. It's also not easy. 
You need to know a lot of things; you're accelerating a lot of "stuff" when you make a pull in your car, and therefore you need to keep track of all that. You're linearily accelerating the erntire mass fo the car, but you're also rotationally accelerating the crank, flywheel, clutch, transmission parts, axles, drive wheels, non-drive wheels, etc.
What you basically need to do, is figure out the change in energy between each of the points. That will allow you to figure out the work that was done in that period of time, which is horsepower!
You need to know a lot of things; you're accelerating a lot of "stuff" when you make a pull in your car, and therefore you need to keep track of all that. You're linearily accelerating the erntire mass fo the car, but you're also rotationally accelerating the crank, flywheel, clutch, transmission parts, axles, drive wheels, non-drive wheels, etc.
What you basically need to do, is figure out the change in energy between each of the points. That will allow you to figure out the work that was done in that period of time, which is horsepower!
05-24-2004, 11:27 AM
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Re: (Sinner)
Check the Aem EMS tuning board - somebody made an addition to the maths library a good while back that did what you are trying to do... the AEM Log software did the calculations though, but its worth a look.
05-24-2004, 05:43 PM
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Re: (Muckman)
I think I am not going to do horsepower but do the time difference from one rpm point to another. That should work for comparing runs.
Nick
Nick
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05-24-2004, 05:49 PM
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Re: (Sinner)
Yeah I think if you want to calculate torque and horsepwer accurately you need to know all kinds of things such *** frontal area co. of drag etc but for ballparking it just to compare runs just make sure your on a flat surface and there are comparable atmospheric conditions??? I think.... (I know nothing)
05-24-2004, 06:09 PM
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Re: (Sinner)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Sinner »</TD></TR><TR><TD CLASS="quote">I think I am not going to do horsepower but do the time difference from one rpm point to another. That should work for comparing runs.
</TD></TR></TABLE>
I used to use that for tuning all the time, it works great!
What you might want to consider, is not just gauging the time difference for a wide rpm range. Instead, do the time difference between each point, and then find the derivative, as in the time per change in revolutions per minute.
Toss that information into excel, and make it solve for a best fit curve. That will essentially give you an acceleration/thrust curve, which will let you compare runs.
</TD></TR></TABLE>
I used to use that for tuning all the time, it works great!
What you might want to consider, is not just gauging the time difference for a wide rpm range. Instead, do the time difference between each point, and then find the derivative, as in the time per change in revolutions per minute.
Toss that information into excel, and make it solve for a best fit curve. That will essentially give you an acceleration/thrust curve, which will let you compare runs.
05-24-2004, 06:23 PM
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I found a link with the formula for RPM vs Time = power, just incase someone does a search and needs the info.
http://members.fortunecity.com...7.htm
http://members.fortunecity.com...7.htm
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