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Thread: Returnless Fuel System - Operation

  1. #1
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    Question Returnless Fuel System - Operation

    I'm trying to figure out what all would need to be done to change over a return style fuel system to a returnless system.

    So I found an old thread, which somewhat asked the same question I had, but not to the level of detail I had hoped. So I am starting a new one for search purposes...

    Quote Originally Posted by Rara View Post
    It could be done, but it would require swapping in/out a number of other components to allow the fuel delivery to be controlled properly. Not something you could do in a weekend unless you had worked it all out and had all the correct parts on hand.
    so... what components would be needed?

    I'm trying to think through what all happens, is an open loop system?

    -ECM turns on fuel pump
    -fuel pump pumps fuel through line
    -fuel reaches pressure regulator, which regulates incoming fuel to set pressure
    -Returnless: ECM monitors fuel pressure regulator creating a closed loop and adjusts fuel pump output??
    -ECM turns on injectors accordingly
    -injector sprays fuel into cylinder
    -Return: excess fuel cycles back to tank??

    Reason why I ask is that my 2005 ST220 fuel rail is a returnless rail, but it has no electronic monitoring fuel pressure sensor like my 2005 Escape rail has on it. So I am wondering how the returnless system operates on the ST220 Mondeo. I am assuming it would be an open loop system since there is no feedback to the ECM regarding fuel pressure, which if this is the case then I don't see why a returnless fuel rail couldn't be swapped into a return style car. If this is true then all you would need to do (again making an assumption here) is remove the unused return line and plug the corresponding ports on the tank. This should not have any effect on the fuel pump as it only has an inlet and an outlet. The only thing that could potentially be effected is the output from the ECM to the fuel pump, however if the system is truly open loop and the ECM is not monitoring the fuel pressure regulator then there would be no change in the ECM output to the fuel pump anyway.

    So that said... thoughts, comments?


    EDIT: I just thought of this... unless the ECM is monitoring fuel pressure at the fuel pump, but this would not make sense as it would need to look at the pressure after the regulator where it matters...
    -Mike
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  2. #2
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    I have always thought return was more ideal for higher hp applications.
    '98 SVT E0 BLK/MNB#1663 3L Always broke.
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  3. #3
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    Quote Originally Posted by Beans View Post
    I have always thought return was more ideal for higher hp applications.
    Only benefit that I could see from return vs returnless is the possibility that the fuel temperature could be cooler with that of a return style. Other then that... everything else would be the same I would think.
    -Mike
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    I'm sure someone will chime in, but i know for a fact that some Terminators owners convert to return, i believe SRT-4 owners too...
    '98 SVT E0 BLK/MNB#1663 3L Always broke.
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  5. #5
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    The difficulty here is that I need to use the returnless fuel rail regardless of whether it functions with the current system as a return style or if I convert the existing system to returnless. So if the benefits of a return style are in fact just cooler running fuel temps then I won't be completely capitalizing on that because the fuel rail I have to use is not built to operate that way and the fuel will not be flowing through it the same way it would with a return style fuel rail. I guess we'll see what someone with more experience chimes in with. Otherwise I'll bounce this question off some of the engineers on the engine team at work next week when I get back on the 5th.
    -Mike
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  6. #6
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    why not just use the NPG fuel rail mod? it was designed to allow the use of the returnless fuel rail on return system cars.
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  7. #7
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    I know you'd like to use that rail and you still might be able to, but for your plans and power level I would only do return style.
    -J
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  8. #8
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    Quote Originally Posted by biminiLX View Post
    I know you'd like to use that rail and you still might be able to, but for your plans and power level I would only do return style.
    -J
    What's your opinion as to why the return system should be used?
    -Mike
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    98 SVT Contour - HoK TruBlue|CF roof|#49/6535 DOB 3/25/97|550whp here I come|Follow my extremely slow 3L/turbo build here Link
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  9. #9
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    Quote Originally Posted by CSVT#49 View Post
    What's your opinion as to why the return system should be used?
    Safer for big power IMO, thats why you rarely see the big HP cars run returnless, they are almost 100% return.
    I like a mechanical regulator and more supply over electronic sensors calculating how much fuel I need when I drop the hammer. More reliablity with a return also, but I never had a problem with the FPRS in my '04 Cobra but lots of my friends did.
    -J
    '99 SVT Silver
    Clean DD
    '91 LX Bimini Blue
    427"/88mm @ 16psi....yeah 4 digit power

  10. #10

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    Most I have seen work like this.

    http://autospeed.com/cms/title_Modif...7/article.html
    This one has a little at the bottom about returnless.
    http://autospeed.com/cms/A_2636/article.html

    If I were you I would use the old feed as the return line and buy some -6an ss braided and use that to make the new feed. Its not going to be plug and play though.
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