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This fluid dynamics thing is not that easy to understand < at least not to me> you guys are saying that the dia of the line does not make a difference psi, so a 1" pipe that is 100ft tall will take the same energy to lift as a 2" pipe 100ft tall, but what about the amount < volume> of liquid coming out the end? If ya read all the fuel pump guys versions for the need of a larger fuel system it kinda makes sense, can some one link together both pressure and volume as related to a racing fuel system? As is, it seems to me that a small pump with a large hose should work for the most part, so why are we buying large pumps? I started out with 2 Holley reds with 2 3/8 fuel lines feeding a 850 dp Holley and just about every one busted my chops about it

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EMarine, the concept is hard to grasp I admit!

I too was skeptical, it went against what I felt was common logic. But fluid dynamics have thier own logic ways of working.

In your example the 2" diameter 100" column of fuel would have more mass. But the PSI pressure at the bottom would remain the same for both diameter pipes. The difference in mass of the 2 columns wont make a difference.

As a Example, take a 100 gallon Fish tank that has alot of water mass. Run a 1/4" diameter hose connected from the bottom of that tank up the side of it to the top.

Fill that 100 gallon Fish tank with alot of water mass and see what happens to the Low mass 1/4" column hose.

Will the Large Mass volume of the 100 gallon tank force water to gush out of the low mass 1/4: tube??

No, It will self level itself to the tanks water level. Why is that when you have that 100 Gallon mass? Fluid Dynamics!


To answer your question about Volume. The Pump works against pressure not mass. With both pipes having the same PSI but different Diameters.

Once fuel starts moving, line friction comes into play. The Faster the fuel moves, the more line friction and the more pressure is created in the line. Smaller lines if to small for the pump will create more resistance to any pumps rated flow vs a bigger line.

The bigger lines extra fuel mass will have no effect on the pumps abilty to flow its rated Volume. To small a line or too many turns and orifices will. mike





EDIT!!! Id Like to thank Jamesc, RobbMC and Firefighter Ron For Schooling me on this in the past!

Cokebottle kid I dont think discussions like this are ever Pointless.