Pump loop pressure

Discussion in 'PSI Superchargers Tech Questions' started by GregM784, Aug 26, 2019.

  1. GregM784

    GregM784 Member

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    Blown 468 BBC
    8:71, bird, 110 pump, hats only
    7.60 index car.

    Going to loop off some of the fuel pump.

    My idle check is 6psi. Where should i aim on my pump loop check? 10psi?

    I want the loop in effect at the leave, correct? Whatever the system pressure is at launch, it should be already flowing the pump loop, or it'll be super rich. I understand i can use it like a enrichment circuit, but the complexity isn't needed on this combo.

    Thanks guys for the ideas/answers. Happy Monday.

    Greg
     

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  2. td3829mk

    td3829mk Member

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    30-40
     
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  3. GregM784

    GregM784 Member

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    Thanks TD3829mk. that's the bench mark? No connection to your leave RPM/fuel pressure? our fuel pressure not that high (leave @ idle)
     
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  4. Mike Canter

    Mike Canter Top Dragster
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    It depends. You can use the pump loop to bleed off pressure at idle if it is too high or you can measure the pump outlet pressure a idle and put it a little above that so it comes on when you launch. Either way it will be on during the run. No real relationship between the idle return and the pump loop. To my liking the idle return is a little low so requires the barrel valve leak down to be a higher percentage. The norm is 8 1/2- 9 1/2 but if it is idling well with good clean off idle response then leave it alone.
     
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  5. GregM784

    GregM784 Member

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    Thanks Mike.
     
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  6. Sandracer695

    Sandracer695 Member

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    Make sure you put a jet in the pump loop. You can split the area of the main jet. Half in the pump loop and half in the main jet. If you have a .140 main now you can put a .100 in pump loop and a .100 in main. Pump loop check at 40psi. It will be slightly richer than just a .140 in the main only.
     
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  7. Fuel Cars

    Fuel Cars AA/AM

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    Greg, on mine, I have the pump loop/pump sizer set @ 37 psi with .125 return pill so I can run .075 main pill.
     
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  8. 32 bantam

    32 bantam Member

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    If he is "sizing" the pump...why not just jet it for the GPM he does not need and set psi check valve less than idle pressure so it is always pumping less fuel to the engine.
     
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  9. 32 bantam

    32 bantam Member

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    Oh...never mind.....The sizer psi would then be the idle pressure !!!
    It needs to be above idle pressure....
    But just a few lbs above idle would work?
     
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  10. Mike Canter

    Mike Canter Top Dragster
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    That’s what I said above
     
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