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i think most 9-11 second car owners on this board must own stock in magnafuel, as they all seem to run their 1200-1500 dollar setups on cars that in no way need them( na)

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yea but they look purty

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i think most 9-11 second car owners on this board must own stock in magnafuel, as they all seem to run their 1200-1500 dollar setups on cars that in no way need them( na)

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yea but they look purty

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Yes they do! I have 1/2" lines on my low 11's sb Volare only because the stock lines were shot from the car sitting for YEARS in a field and the only lines my local speed shop had were 1/2". I could have ordered some smaller lines but would rather keep as much money local as I can, (even so that they run chebbies over there). I was running a Holley Black till it died between rounds and slammed a Holley Blue on it and it never missed a beat.

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Yet ANOTHER fuel-line topic ...


And a 3/8 line will handle THE FASTEST car on this board.

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That's why I have a 1/2" line on my car!

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I guess I used the wrong size line because mines 1 1/4

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bigger will NEVER kill your engine like a lean
condition will

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Going lean in the lights can cost you more than most fuel systems.

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Going lean in the lights can cost you more than most fuel systems.

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i have 3/8 at 650 hp, with a carter mechanical race pump. my pressure gauge hardly drops at all during a run, so i couldn't tell you how close i am to the limit w/my combo. put a fuel pressure gauge in it. then you know.

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The only true test is watching the gauge throughout a run. If it will hold the same PSI start to finish, you are good to go.
On fuel line size , so many variables come in to play, it is very difficult to put a hp number to any particular fuel line size.
Length of the line, number of bends, G force, pump pressure
and any variance in voltage will change the rate of flow. So the real answer is "it depends".
The end result needs to be will there be enough fuel delivery to keep the bowls at the same level at all times. That is a lot easier with four needle and seats on a tunnelram/dual four combo. A high hp dominater is one of the toughest to feed. Only two needle and seats, and often lots of hp.

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...Too big of a fuel line can be a problem if the cell and pump are in the back of the car and the car leaves extremely hard...

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The problem with this method (BG below) is it totally ignores the weight of the vehicle. Here's a test I plan to preform someday soon: Take fuel bowls off carb and put them in cans and turn on the fuel pump and see just how much the pressure drops at maximum float drop.

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Fuel pressure has nothing to do with how much volume the system will support, if you do that test and you have any pressure at the gauge you need bigger fittings, lines or needles and seat

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One of my Mopar manuals has a line about fuel line diameter and acceleration and it's totally wrong. I'm pretty sure they deleted it from later manuals. To reiterate: the pressure generated from accelerating a column of fluid is independent of the area of the column (or in this case, the diameter of the fuel line). The pressure generated is the product of the fluid density, acceleration rate, and the height/length of the fluid parallel to the direction of acceleration. Cross sectional area doesn't figure in at all. For instance, the pressure 50' below the surface of Lake Superior is the same as the pressure 50' below the surface of lake Huron, even though one has a much larger area. Let's put this myth out of its misery.

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doesn't the inertia from the weight of the entire fuel column come into play? Essentially if you think of the fuel in the fuel line as solid, the force generated back to the pump cavity (and thus the pump vane/motor) would be it's mass times horizonal acceleration. The larger the mass (Diameter), the more force is put on the pump vane to keep it all moving forward.

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What do you think?

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Let's put this myth out of its misery.

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Cab, when using the 'Quote' feature you need to pay attention to the "quote" and "/quote" markers so you don't get people's quotes mixed up with your replies. I've corrected your reply in attempt to straighten it out.
The test I proposed is a type of load test, where the pressure is measured WHILE the system is flowing. In this way pressure losses across lines and fittings are accounted for (the ones before the regulator anyway). I can also measure flow rate at the same time. I can guarantee you that if there is no pressure shown across the needle/seat under full flow that there is a big enough pump to change that. The whole point is to determine if the pump/filter/lines/fittings/etc are more than adequate to supply a pair of .120" needle assemblies mounted in standard Holley center-hung bowls. My system (Mallory 140, 1/2" line) flows 1 gallon in 25 seconds to the regulator and hauls my heavy '68 Barracuda to low 10's@ 129mph. At the end of last year I was running 60% ethanol but never got around to trying pure E85. I use an Innovate LM-2 wideband to tell me if the engine goes lean, and it hasn't. My combo liked the indicated AFR around 12:1 but wasn't very sensitive to AFR ET or MPH-wise in that neighborhood.

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The problem with this method (BG below) is it totally ignores the weight of the vehicle. Here's a test I plan to preform someday soon: Take fuel bowls off carb and put them in cans and turn on the fuel pump and see just how much the pressure drops at maximum float drop.

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Fuel pressure has nothing to do with how much volume the system will support, if you do that test and you have any pressure at the gauge you need bigger fittings, lines or needles and seat

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thanks for pointing that out, deleting the quote marks I didn't read that reply until this morning

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Where the diameter of the fuel line comes into play is the velocity of the fluid within the line. Head losses or pressure losses are related to velocity squared divided by 2 x force of gravity times the head loss coefficient of the tubing. So essentially a larger diameter tubing reduces the fuel velocity and the pressure losses.

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The mass/inertia of the fluid does come into play, that's why the density is in the the equation. Area doesn't factor in at all.

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So essentially a larger diameter tubing reduces the fuel velocity and the pressure losses.

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In firefighting Pump operations this is referred to as friction loss. The larger the hose diameter the less friction loss given the same hose length and discharge pressure.

Good discussion

My old 446 was using a 3/8 line with a Carter HV 120gph mechanical. The car ran 116mph @ 4100 raceweight...do the math.

The new 572 will be using 8an lines with a Mallory 250 and return style regulator. This motor made 705hp on Dwayne's dyno.



Ron

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The larger the hose diameter the less friction loss given the same hose length and discharge pressure.

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B U T ....a fire-hose is that traveling from a dead-stop to 60 mph in 2 seconds or so !