fuel PSI

Discussion in 'VP44 Pump' started by ramhunter9, Oct 26, 2011.

  1. ramhunter9

    ramhunter9 Supporting Member

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    Well after the turbo swap I noticed a drop in PSI at WOT ..

    Idle is 20psi
    cruising 17-18psi

    Now WOT 9-10 .. WTF ?
     
  2. ramhunter9

    ramhunter9 Supporting Member

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    From my readings .. and someone clarify .. There is a screen on the raptor inlet that could be causing the drop at WOT .

    But if its clogged why wouldn't it drop PIS on idle ?
     
  3. badfish888

    badfish888 Senior Member

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    dave, on our detroits at work they do the same WOT is 2050. the way it was explained to me a school was at WOT the injectors open an additional passage way with bigger holes, causing a more dense fuel mist but dropping pressure from the added passage ways.........if that makes sense, not sayn at all thats wat u got cause i have no clue bout ur injectors, but i have seen it before on other diesels....................my $.02
     
  4. Mopar1973Man

    Mopar1973Man Senior Member

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    Best why to explain...

    As your demand volume of the VP44 increase above the supply volume the pressure will decrease. So now that you capable of turning up the Quadzilla and produce more power it takes more fuel to make said power so there is a pressure loss.

    But now looking deep I would double check the pump for that screen I've heard some say the new ones don't have it but the older ones did have a screen in the suction port.

    Also with the cooler weather the fuel will thicken more so like me on a cold day I can pull deeper into the pressure loss till the fuel in the fuel tank warms up once it does the pressure loss is reduced again like summer time.

    So do a little checking and report back what you find...

    EDIT:

    Also do you have a snubber/needle valve on your gauge or is it just plumbed into the fuel system?
     
  5. ramhunter9

    ramhunter9 Supporting Member

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    No snuber , line from tank to raptor .. ya so Guess I can pinch it off
    I will be checking the screen after work today .

    I also should note MoparMan is correct this was ran on #10 . Ran on 6-7 PSI at WOT 14-15
    So its the higher I go in programing the less PSI at WOT

    I hope that screen is dirty
     
  6. Mopar1973Man

    Mopar1973Man Senior Member

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    Another good question do you have the stock line between the stock fuel filter to the VP44? If so there is you restriction...

    [​IMG]

    Compared to 1/2" Big Line fitting...
    [​IMG]

    Or side by side...
    [​IMG]

    But still even my AirDog 150 doesn't drop that much... You've got a Raptor 150 which is the exact same pump just less the filters.
     
    Last edited: Oct 27, 2011
  7. ramhunter9

    ramhunter9 Supporting Member

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    Mike , I have the OEM line from the VP44 to the OEM filter .. And I cracked the raptor open and the screen was spotless . Ran the truck on #2 setting and same thing .
    I did notice that at idle it bounces from 21-16 and crusing is 16-17 but at WOT still drops to 9-10 ?

    If the fix is the new fitting ... link me to a place to get it .

    On a side note ... changed my T-stat and that fixed the putting it into drive and killing it thing at first start up . My gauge now reads 190 with hi idle within min 's
     
  8. ramhunter9

    ramhunter9 Supporting Member

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  9. rambob

    rambob Senior Member

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    wow!
    yea, thats your problem. 1/4" difference
     
  10. Mopar1973Man

    Mopar1973Man Senior Member

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    Last edited: Oct 27, 2011

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