Supercharger flow rates

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by d.kirkalkyburner, Sep 20, 2017.

  1. d.kirkalkyburner

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    Looking for information on the cfm flow rates of 671 871 superchargers in std and high helix per revolution. Thanks Awesome site and very informative
     
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  2. Kamikaze85

    Kamikaze85 Member

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    If someone has some ballpark figures for "off the shelf" and "all tricked out" 14-71 blowers, I would really like to know as well.
    Just wondering what you get for the added cost.
    Sorry to hi jack the thread :)
     
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  3. Comax Racing

    Comax Racing Member

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    If you go to Fuel Injection enterprises, Spud has a tune up calculator that includes blower output in all the various sizes. These are ball park but that's what it seems you are looking for. You just need to get a user name and password, no cost works good.

    Corey
     
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  4. bob szabo

    bob szabo FC / altered

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  5. bob szabo

    bob szabo FC / altered

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    An example is provided for an 8,000 RPM blower speed.

    A standard diameter 6-71 with seals is 430 ci / rev. x 8000 blower RPM = 3.44 million ci per min. / 1728 ci per CF = 1,991 CFM w/o leakage.
    A standard diameter 8-71 with seals is 470 ci / rev x 8000 blower RPM = 3.76 million ci per min. / 1728 ci per CF = 2,176 CFM w/o leakage.

    A blower with fresh seals too tight to turn over by hand will leak less than a blower loosened up from a few runs. After a few runs, manifold boost in blowers with conventional bottom openings will deflect rotors to reduce top seal clearance and may leak more than blowers with delta openings

    A blower with a delta lower opening will leak less than a blower with a conventional opening due to shrouding around the rotors.

    A blower feeding a lower boost will leak less than a blower feeding a higher boost.

    A blower feeding a larger displacement engine will have a lower boost with less leakage. (Note: A larger engine has more friction so power is not necessarily increased with engine size).

    A blower fed with more fuel in the hat will have a lower manifold temperature and a lower boost with less leakage than a setup with hat and port nozzles with more fuel in the ports.

    We used our jetting calculator, ProCalc, for setting up our fuel system based on the size of the blower and the amount of fuel going through the jetting. We de-rated the blower with a blower efficiency provision in the calculator. We use values from 98% for flesh blower seals down to 90% for blowers with more than 50 runs on the seals for our combination. For our previous racing, that worked real well for tuning. We could maintain spark plug color real well with air to fuel ratio tuning from the calculator with the proper de-rated blower efficiency for blower wear. We most always ran a wisker from our dial in right out of the trailer.

    Bob Szabo
    http://airdensityonline.com/procalc/
    http://racecarbook.com
     
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