thoughts on adjustable fpr?
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This is a discussion on thoughts on adjustable fpr? within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; i want to get a adjustable fpr becausei think im lossing pressure durring start up and closed loop driving why ...

  1. #1
    Registered User sxcrxy's Avatar
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    thoughts on adjustable fpr?

    i want to get a adjustable fpr becausei think im lossing pressure durring start up and closed loop driving why you may ask?

    i have decaped stockys ever since ive done that the car is hard to start (flow tested at 799cc) (puff of black smoke when started) could be not atomising the spray proply due to loss of pressure and floods the motor???

    (oly someties) also have a walbro 255, when i drive or just letting out the clutch it does a quick hesatiation and my ideband leans out for that split second ( note this problem was there before i decaped the injectors, but after i changed my feul pump)

    if i do get a new fpr do rails have to be changed? or can they withstand higher pressure
    and how do you actually adjust it ? i want to get a sardd fpr
    piping lenght does that matter a well?

    i understand factory one is 1:1 ratio 15 psi boost meaning 55psi feul pressure for eg whats the ratio on the sard from factory? without adjustments
    ive been told im losing feul pressure and im leaning towards the same thing because ive checked everything eleese lol beside feul filter?

    car runs fine other than that

    things ive checked
    - the tune it self (cranking pulse width injector timing etc etc)
    - leaks vaccum and boost
    - fuel line leaks and rails
    - fuel pump operation and changed the filter on the pump

    i do let the pump prime everytime before i start it or could this problem be fixed siply with a new oem fpr?

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  3. #2
    Moderator Donkey's Avatar
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    Well considering hundreds/thousands of Subaru WRX owners have run decapped injectors with out needing an adjustable fuel pressure regulator I don't see why you would need one. Mainly because injector pulse width and latencies along with proper injector scaling produce no more fuel at idle than stock,unmodded injectors. You are putting the cart before the horse. Have you looked at you fuel trims? Have you even verified your fuel pressure with a gauge even? If the stock FPR is one is bad,replace it with another stock one. At sealevel with the reference line removed from vacuum you should see around 43.5 psi. At idle fuel pressure should be between 35-38 psi.
    Last edited by Donkey; 12-06-2012 at 07:10 AM.
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  4. #3
    Registered User sxcrxy's Avatar
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    Quote Originally Posted by Donkey View Post
    Well considering hundreds/thousands of Subaru WRX owners have run decapped injectors with out needing an adjustable fuel pressure regulator I don't see why you would need one. Mainly because injector pulse width and latencies along with proper injector scaling produce no more fuel at idle than stock,unmodded injectors. You are putting the cart before the horse. Have you looked at you fuel trims? Have you even verified your fuel pressure with a gauge even? If the stock FPR is one is bad,replace it with another stock one. At sealevel with the reference line removed from vacuum you should see around 43.5 psi. At idle fuel pressure should be between 35-38 psi.
    thing is i dont have fuel pressure gauge :/ anyway to tellwithout one via roraider or something?

  5. #4
    Moderator Donkey's Avatar
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    Nope. You need a fuel pressure gauge to accurately diagnose/rule out fuel pressure.
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    Registered User Heide264's Avatar
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    Agreed with Donkey. I don't have anything against other fuel pressure regulators, but I highly doubt yours is insufficient unless it is broken.

    Maybe a local garage will check it for you for cheap.
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  7. #6
    Registered User sxcrxy's Avatar
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    Quote Originally Posted by Heide264 View Post
    Agreed with Donkey. I don't have anything against other fuel pressure regulators, but I highly doubt yours is insufficient unless it is broken.

    Maybe a local garage will check it for you for cheap.
    weell im a mechanic my self but i just need a a gauge to check it lol id rather spend $50 on a gauge and keep it then spend $50 for someone whos gonna do it once for me,

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