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Old 11-29-2015, 10:54 PM   #1
freezy74
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Default Driveshaft RPM to MPH

Is there a math formula for this? I'd like to program it into my Holley for the data log. I have it doing converter slip already, figured it was possible to do MPH also.

Thanks.
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Old 11-29-2015, 11:44 PM   #2
64duece
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Default Re: Driveshaft RPM to MPH

Shaft Speed (RPM)/Gear Ratio*Tire Diameter (in feet)*60/5280

Calculate Circumference= (Pi*Diameter)/12 = Diameter in Feet
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Old 11-30-2015, 10:51 PM   #3
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Default Re: Driveshaft RPM to MPH

Quote:
Originally Posted by 64duece View Post
Shaft Speed (RPM)/Gear Ratio*Tire Diameter (in feet)*60/5280

Calculate Circumference= (Pi*Diameter)/12 = Diameter in Feet

or the more simple math

MPH = (Driveshaft rpm * tire diameter in Inches ) / ( Gear Ratio * 336)
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Old 11-30-2015, 10:53 PM   #4
freezy74
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Default Re: Driveshaft RPM to MPH

Quote:
Originally Posted by 64duece View Post
Shaft Speed (RPM)/Gear Ratio*Tire Diameter (in feet)*60/5280

Calculate Circumference= (Pi*Diameter)/12 = Diameter in Feet
Ok Thanks. I'll try to figure this out.
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Old 11-30-2015, 10:55 PM   #5
freezy74
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Default Re: Driveshaft RPM to MPH

Quote:
Originally Posted by S2H View Post
or the more simple math

MPH = (Driveshaft rpm * tire diameter in Inches ) / ( Gear Ratio * 336)
Got that to work quick, thanks!!
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Old 11-30-2015, 11:46 PM   #6
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Default Re: Driveshaft RPM to MPH

Funny, my 1-2 shift is 101.5 mph, and it gets there in 2.6 seconds lol...I love data....
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