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Will the fuel system benefit from a larger fuel line?

  1. Dec 23, 2015 #1
    Hello, I am working on a automotive fuel system for a school project and one of the problems is not enough fuel at higher rpm's. Would a larger fuel line help this problem? The pump has been determined that it should be powerful enough for the necessary supply and wondering if there can be improvements made in the plumbing itself to solve this problem. I have yet to take fluid mechanics but from my understanding the flow rate will stay the same throughout the fuel system but the fuel will be harder to pump through a smaller line due to more pressure(friction) loss. But where all this gets confusing for me is since there is a pressure regulator, how much does all this stuff about pressure lost matter? My theory is that since there is a bigger pressure loss through a smaller line, it takes longer for the pressure regulator to build up the necessary fuel pressure in a smaller line versus a larger one, therefore making it harder for the fuel supply to keep up with the engine needs at higher rpm's. Can I get some confirmation on this whether its accurate or inaccurate? Also if someone can help me make sense of how big of a factor bends in the line make and help make sense of plumbing in general as in some basic laws in designing a good plumbing system. Thanks, any info and additional resources greatly appreciated.
  2. jcsd
  3. Dec 24, 2015 #2


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    Are you sure it's a fuel supply issue and not a fuel/air mixing issue?

    The flow rate is the same at all point because the fuel can't be significantly compressed. That doesn't mean it will stay they same if a large pipe is replaced with a small one or a restriction is added to a pipe. That depends on how the pump works. Sometimes a restriction will cause a pump to slow down and that will reduce the fuel flow rate.

    Does your system have a loop? On many cars the fuel pump delivers excess fuel to a chamber near the engine and any excess not used by the engine is returned to the tank. If you are still getting fuel returned to the tank at high rpm then that would indicates the fuel pump and pipe work is ok (I mean for size, there could still be other issues like a blockage). If not then you might need a bigger pump or bigger pipes.
  4. Dec 24, 2015 #3


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    Perhaps check for a blocked fuel filter or a carb air leak?
  5. Dec 24, 2015 #4


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    What led you to this conclusion?
  6. Dec 25, 2015 #5

    Ranger Mike

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    whoa up there partner...
    what is the engine application?
    is it carb or fuel injection?
    how many psi is fuel pump and where is it located?
    what size fuel line is pick up, is main fuel line?
    is this a drag race situation?
    how much wide open throttle time are we talking about?
  7. Dec 29, 2015 #6
    A larger fuel line will help only if your fuel line is too small. Ranger Mike is correct, there is much too little information and how are you determining you are running out of fuel? You may be running out of ignition. If you are going by an exhaust oxygen sensor, they only read oxygen. Missfires will leave unused oxygen enter the exhaust and fool the sensor.
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