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Thread: Supercharging with AFM

  1. #1
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    Default Supercharging with AFM

    Can anyone tell me how this works? Not finding information on it anywhere. I'm having a problem understanding how a positive displacement supercharger works with AFM, considering the supercharger pushes X amount of air into the intake with each revolution of the engine. When AFM cuts the engine in half, it seems to me like the active cylinders are now taking the same air meant for 8 cylinders, which should increase those cylinder's compression by quite a bit. GM sells the LT4 with AFM active, and they seem to make it work.

    So, how are they making AFM work without screwing the engine up? I'm in the initial planning stages for a 5th gen LT1 based 427, and I may at some point want to supercharge it and if I do I plan to keep AFM active. I know a lot of folks don't like the system but I do.
    Last edited by Telco; 3 Weeks Ago at 03:01 PM. Reason: Corrected a mistype

  2. #2
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    If you're light enough on the throttle to be in 4 cylinder mode, you're surely light enough for the supercharger to be bypassing. I'm guessing this is enough?
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  3. #3
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    I guess that could be. Wish I knew more about forced induction. But, I was under the assumption that a PDSC displaces X amount of air per revolution regardless of how many cylinders are opened, so cutting them in half would mean that double the air is being forced into each cylinder.

  4. #4
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    Quote Originally Posted by Telco View Post
    I guess that could be. Wish I knew more about forced induction. But, I was under the assumption that a PDSC displaces X amount of air per revolution regardless of how many cylinders are opened, so cutting them in half would mean that double the air is being forced into each cylinder.
    The amount of air the blower would be pushing is nil for 2 reasons: 1 the throttle is barely opened at all and 2 the bpv would be open.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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