EFI Fuel pump?

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by pdxmotorhead, Jan 18, 2013.

  1. pdxmotorhead

    pdxmotorhead Been here awhile

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    890
    Location:
    Portland OR
    #1
  2. Head2Wind

    Head2Wind MotorcycleMayhem

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    the 990 does not have a return line, it "dead heads" to the injector rail. The FPR (fuel pressure regulator) is just after the pump and after the 7-10 micron rated filter, it just dumps the excess fuel back into the tank..

    the 950 uses a completely different system and substantially lower fuel pressure... the 990 runs at ~51PSI the 950 is 1.5-2PSI
    #2
  3. pdxmotorhead

    pdxmotorhead Been here awhile

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    890
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    Portland OR
    HMM. I do a lot of tuning on EFI race engines,, cars, some bike powered dirt cars, I found that pumps are way happier moving fuel than dead heading to the injectors.. I bet you could reduce the EFI fuel issues with a very small bleeder line
    from the fuel rail back to the tank.. Enough so the fuel in the lines does not heat soak and so the pump gets cooling..
    It could have a .020 orifice in it just so the fuel moves...

    Be interesting to have a temp probe in that line right after the pump...


    Just mulling ove rthe important world problems, fuel pumps, beer selection, the ususal...

    Dave
    #3
  4. Peanuts

    Peanuts Long timer

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    At the kind of MPG we get out of the 990 I think there is quite a flow through that pump ;)
    #4
  5. StevenD

    StevenD Hmmmm, dirt!

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    the stock pump does plenty of bleeding back to the tank via the also in tank pressure regulator. its just the connection to the fuel rail thats a bit longer then with systems that have a regulator near or at the fuel rail.

    Heat can build up in the line but i doubt that is near being an issue.
    #5
  6. Head2Wind

    Head2Wind MotorcycleMayhem

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    Fuel heat could be a issue, and i agree that flowing fuel through the rail would definitely reduce the fuel temps at the injectors, the question would be what would the outcome be? Granted cool/cold fuel can equal greater density and potential power, perhaps the greatest improvement would be related to not boiling the fuel in the rail. At 51 psi that temp is pretty high.

    The challenge with the throttle bodies and the fuel rails is there is very little space to do much of anything like adding a flow through port at the end of the rail..... personally i'd prefer the FPR at the end of the rail with a return line, but as presently designed/built its very crowded in that area already... it would require a new fuel rail design, and to retrofit to an existing throttle body would be difficult.

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    #6