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Thread: selecting a mechanical fuel pump (carbs)

  1. #1
    Join Date
    Jul 2008

    Default selecting a mechanical fuel pump (carbs)

    lets say youve got a 450 hp sbc and your looking for a decent mechanical fuel pump, the choice is between two in your catalog , one pumps 35 gallons per hour and one pumps 80 gallons per hour, but costs a bit more, so you want to know if the smaller pump will work?

    The average advertised weight of a gallon of premium fuel is 6.34 lb/gallon.
    Brake Specific Fuel Consumption or B.S.F.C.
    Brake Specific Fuel Consumption or B.S.F.C. is the amount of fuel required to produce 1 HP for 1 hour. This means that an engine with a B.S.F.C of .5 will burn 1/2 or .5 lbs of fuel to produce 1 HP for one hour. Determining exact B.S.F.C for a specific engine is complicated and requires an engine dyno.
    Based on industry standards the B.S.F.C for:
    Normal Aspirated Engines is .45 - .55
    Supercharged Engines is .55 - .60
    Turbocharged Engines is .6 - .65

    need to calculate fuel required:
    Target Hp * B.S.F.C. = Fuel required in lbs/hr
    450 *.6 = 270 lbs/hr
    Most fuel pumps flow rate is advertised in gallons per hour:
    Lbs/hr / fuel weight per gallon = gal/hr
    270 / 6.34 = 42.6 gal/hr
    but remember pump losses, and a fuel pressure regulator and a return line fuel feed system designs flow requirements ?
    well on a mechanical fuel pump that supplies about 7psi at the pump, getting more than 4-5 psi at the carb, under hard acceleration is going to be a challenge, due to flow restrictions, pumping losses, etc. youll find that the 80 gallon pump matched to a quality fuel pressure regulator,is about the minimum required, and a 100-110 gallon flow at 7 psi would be a nice option

    related diagrams

    this basic fuel system, and line size will work to over 650hp or more with the correct pump and regulator, youll want a MINIMUM of AN #6 or 3/8" fuel lines on both the feed and return lines on a 450 hp engine
    Last edited by grumpyvette; 04-14-2010 at 07:17 AM.

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