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Thread: Cubic Feet Per Minute (CFM)

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    Mechanic Slymanrs2's Avatar

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    Cubic Feet Per Minute (CFM)

    How do you work out the CFM for the following engine?

    4.6 Litre V8 (278 cu in)
    94mm bore
    82mm stroke
    5,500rpm (6000rpm MAX)

    Escort Mk1 Cosworth YBT build.

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    Spanner Monkey sierra1off's Avatar

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    Re: Cubic Feet Per Minute (CFM)

    The volume of the 8 cylinders is 278 cubic inches, which takes 2 revolutions to pass through.
    So 1 revolution passes 139 cu. in.
    at 5500rmp it flows 76450 cu.in
    convert this to cfm (/ by 1728 ) = 442cfm.
    This assumes a perfect flowing intake, head, and exhaust To be realistic you reduce the cfm by 15% to allow for all the restrictions (or less if its forced induction)
    So 442 x .85= 375 cfm maximum flow

    Suprising isnt it that we dont need those big Holleys

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