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Re: how much hp will 3/8 fuel line handle?
[Re: dizuster]
#605021
02/08/10 01:50 PM
02/08/10 01:50 PM
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Joined: Jan 2003
Posts: 5,875
communist bloc of new jersey
jamesc
master
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master
Joined: Jan 2003
Posts: 5,875
communist bloc of new jersey
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Quote:
I just don't see why you think the mass of the fuel can be ignored.
it does not apply to this discussion, period
again...fluids exert force in all directions. the additional loading from the mass is distributed to the WALL of the container (hose, tubing etc.) not the bottom or in this case pump discharge.
look at it this way... you have two tanks both 30' tall full of water. one is ten feet in diameter the other is 150' in diameter. put a pressure gauge at the bottom of both tanks and the reading will be the same 12.99 PSI. what WILL be different is the wall thickness of the larger diameter tank will have to be greater than the smaller tank because the additional mass of the much greater quantity of water is exerted on the WALLS of the container not the bottom. the ten foot tank would probably hold up being made of sheet metal, try that with the big one and you'll have a flood.
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Re: how much hp will 3/8 fuel line handle?
[Re: emarine01]
#605027
02/08/10 07:45 PM
02/08/10 07:45 PM
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Joined: Jan 2003
Posts: 6,591
Canton, Ohio
Sport440
master
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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Quote:
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 
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.  
Last edited by Sport440; 02/08/10 07:51 PM.
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Re: how much hp will 3/8 fuel line handle?
[Re: dizuster]
#605028
02/08/10 07:50 PM
02/08/10 07:50 PM
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Joined: May 2008
Posts: 1,131
Thigh-Gap Junction
@#$%&*!
New user name, Same old jerk!
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New user name, Same old jerk!
Joined: May 2008
Posts: 1,131
Thigh-Gap Junction
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Quote:
I just don't see why you think the mass of the fuel can be ignored.
And who said that the mass of the fuel could be ignored? NOBODY! FYI: Density (one of the 3 terms in the applicable equation) is the ratio of mass to volume. The whole point is that the AREA of the fuel line (diameter, effectively) doesn't have any affect on the pressure generated by accelerating the fuel. Also keep in mind that the fuel line is attached to the vehicle and forces generated from acceleration are transferred to the vehicle through the attachment points.
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Re: how much hp will 3/8 fuel line handle?
[Re: Sport440]
#605029
02/08/10 08:06 PM
02/08/10 08:06 PM
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Joined: May 2008
Posts: 1,131
Thigh-Gap Junction
@#$%&*!
New user name, Same old jerk!
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New user name, Same old jerk!
Joined: May 2008
Posts: 1,131
Thigh-Gap Junction
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Quote:
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!
Good example.
Technically speaking, it's not fluid dynamics, that example is of Hydrostatics since the liquid isn't flowing. For all skeptics, check out equations 2 and 3 here: http://en.wikipedia.org/wiki/Hydrostatics
Quote:
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
Good post! This is what people should be concerned with AND THIS is where we're talking Fluid Dynamics.
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Re: how much hp will 3/8 fuel line handle?
[Re: emarine01]
#605031
02/09/10 06:50 AM
02/09/10 06:50 AM
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Joined: Jan 2005
Posts: 3,640
Oakland, MI
dizuster
master
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master
Joined: Jan 2005
Posts: 3,640
Oakland, MI
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After much thought... I agree now that the diameter does not effect pressure or load on the pump. Pressure is pressure. I was confusing the idea of accelerationg having an effect on the fuel vs. diamter having the effect. To clarify my thinking. The harder the car launches, the higher pressure will be seen at the pump right? But I now see that it has nothing to do with the diameter. I kept thinking that the fuel column weight would be applied directly to the fuel pump vain (vane? sp?) When I thought about the pump more specifically, I realized that the orfice size of the pump wasn't changing when the fuel line size changed. So if the same area of pressure from the pump port orfice wasn't changing (meaning area), how could the diameter of the fuel line possibly effect the pump?!? That opened my eyes to the concept of diameter not effecting the force. Thanks guys for taking time to explain. I know it must be frustrating some days, but at least rest knowing that you've opened another's eyes on the subject. On more person now to fight old wive's tales about fuel line diameter! Now I see why I got an "A" in statics, and only got a "B-" in fluids.
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