Technical > Spud Miller's Cave

Mathematical gymnastics

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retroboy:
Hi Spud.
A year or two back you gave me a simple formula to work with based on the results from your NA tune up calculator to work out the difference between the pill and nozzle sizes at a lower RPM than the 8000 in the calculator. I mean if a person runs the figures in the calculator how to read them at a lower RPM? Does that make sense? I've lost them, can you help again please?
Cheers
Tony

Spud Miller:

 No prob!

 It's just a proportional thing. On this type of equation, the thing to ask yourself is: Is the flow 0 at 0 RPM? (yes) In that case, this type of equation (cross multiplication) will work great! Very accurate.

Let's say your pump flowed 6.63 GPM @ 8000 RPM and you wonder what it'll flow at 6600 RPM...

 6.63             X
-------   =  --------
8000           6600

Multiply 6.63 by 6600 and then divide the result by 8000 and you get: 5.47

So, X = 5.47 GPM which will be the flow at 6600 RPM.


Let's say the calculator tells you that your system pressure will be 128 PSI at 8000 RPM, but you wonder what it'll be at 7200 RPM. First question: Is the pressure 0 at 0 RPM? YUP! Ok then....

128 PSI               X PSI
----------   =   -----------
8000 RPM        7200 RPM

(128 * 7200)/ 8000 = 115 PSI

Sound good?

 Spud

retroboy:
Cheers Mate

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