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25ss
01-24-2005, 03:43 AM
Just got a 100 mph keller speedo.
Thought i saw a thead some time ago on a way to convert air pressure to speed?
Dale!

Mark75H
01-24-2005, 08:44 AM
mph= the square root of (pressure divided by .0145)

or


pressure = (speed divided by 8.417) squared



in physics it is expressed as "Dynamic Pressure":

Q= .5 X P X Vē , where P (rho) = 1.9376 and V is feet per second;
using this I calculated 60 mph (88fps) to be 52.1 psi


exact:
69 psi = 69 mph (kinda easy to remember for a couple reasons, huh?)

approximate:
20 psi = 40 mph
40 psi = 52 mph
70 psi = 70 mph
100 psi = 85 mph
130 psi = 95 mph
147 psi = 100 mph

LakeRacer99
01-24-2005, 02:53 PM
If you haven't checked out Teleflex's Instrument Technical Reference, I recommend it. Even if you don't use their gauges.

http://www.teleflexmarine.com/Pdf/Instruments/TechCat3_1-Instruments-TECH%20REF.pdf

25ss
01-26-2005, 12:03 AM
Thanks thats what i needed.
Dale!