Fuel system (blown alcohol)

Discussion in 'PSI Superchargers Tech Questions' started by Dan Mercier, Jan 21, 2012.

  1. Dan Mercier

    Dan Mercier New Member

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    when to put a pump loup or a hi Speed by-pass, I know that one is before the barrel valve and the other one after ,but which is the difference; thank you.
     
    #1
    Dan Mercier, Jan 21, 2012
  2. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
    Staff Member

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    before or after

    When a check/high speed is in front of the bv, it will open whenever it reaches the preset pressure. Behind the BV, it typically won't start bleeding off until after wide open throttle because it won't see much pressure until then.

    So on a blown motor it comes down to if you want it open at stage or not. That's why a pump loop is usually in front of the bv.
     
    #2
    Will Hanna, Jan 21, 2012
  3. iron468

    iron468 Member

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    ex=my pump is too big ,i have pump loop set at 25psi with 0.090 (around 2 g at 100psi) back to tank if i don't use this the main jets too big for fine tune
     
    #3
    iron468, Jan 22, 2012
  4. bob szabo

    bob szabo FC / altered

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    driving effect

    If a pump loop or high speed is after the barrel valve and the driver lifts, the engine goes fat. When the driver gets back into it, there is less chance of a momentary lean condition and a backfire.

    If the pump loop or high speed is before the barrel valve and the driver lifts, the engine air to fuel ratio is established:
    - first by the fuel split between pump loop or bypass and barrel valve
    - second by the fuel split between engine and bypass

    The engine goes to the back of the line and a momentary lean condition can occur from some fuel systems causing a backfire.

    If the fuel system is jetted properly, there may be a bigger surge in power with the latter for racing where the throttle will be lifted and applied several times. With the former, the engine can go dead rich when the throttle it lifted and hit, reducing the surge in power. We did some tuning with the high speed size and location to control the power surge when the throttle was modulated. Our engine really woke up to part throttle tuning for response after lifting.

    In some engines, we saw the opposite: more response with the pump loop after the barrel valve. Depends on the system.

    Our jetting calculator makes that easy to tune & manage.

    bob szabo
    author of fuel injection racing secrets
    www.racecarbook.com
     
    #4
    bob szabo, Jan 22, 2012
  5. Dan Mercier

    Dan Mercier New Member

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    thank you all for your answers, I'm familiar with Nitromethane and alcohol with my a/fuel or promod but my question is for an hydroplane boat! The rules are the following:
    GM motor, 468 ci, 8-71 supercharged standard helix with 20% overdrive with aluminium Dart heads. It would be about 1200 hp.
    A competition is 4 laps of 1 mile. on the straight line we are full throttle just before the corner, the driver releases the pedal and in the middle of the corner he goes back to full throttle.

    So would you put a pump loop or a bypass after the barrel valve or both? My pump is a Enderley 110.

    Thank you
     
    #5
    Dan Mercier, Jan 23, 2012

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