Carb Size calculator for SC?
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Carb Size calculator for SC?

  1. #1
    These colors don't run BLWN BUX's Avatar
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    Default Carb Size calculator for SC?

    Hi,
    I am new here so please forgiv if this is a redundent question.

    I bought a 22' Placecraft deck/Cat with a 540CI whipple charged set up.
    I an not sure if the enging combo is what it could be.
    I think my carb may be too small. It dynoed 668 HP at 5600RPM @ 6# boost.

    I looked up a carb chart formula and this is what I found

    CI / 1728 X RMP / 2 = "Carb Size for N/A at 100% VE"

    Turbo/ SC applications need a multiplier added as well:
    14.7 + boost PSI / 14.7 = "Multiplier ratio"

    For example:
    I run a 540CI @ 5# boost at 5400 RPM
    540 / 1728 X 5400 / 2 X 1.34 = "1122 CFM carb needed"

    Is this a good formula for carb sizing?

    If so then I think my carb size is too small. I have a Demon (like holy 4150). I think these carbs only go up to like 850 CFM?

    I was thinking about changing blower pullies for more boost; but I am thinking that just going to a bigger carb would probably increase boost on top end by itself.

    Any help would be appreciated

    Chad

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    i'd stay 4150 if you can, you're not gonna like the fuel mileage of a dominator carb. check out some custom carb shops and see if you can find a nice custom 4150 that'll flow over 1000cfm, call it good

    Dare to be different, if it turns out great you can claim you planned it that way.

    Jetboatperformance.com

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    check out the parts forum...there was a few Holley 950's & a 1000cfm carb for sale...might be what ur looking for...just trying to help

    FastRat

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    These colors don't run BLWN BUX's Avatar
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    I would think that any carburetor that is tuned properly would give equivlent fuel milage.

    If A/F ratios are maintained then there should be no change in fuel usage. Yes?

    Sombody can correct me here, I have NO experience with 4500's

    I am preaty good about tuning though, I am an EFI guy after tuning my Corvette folowing many changes.

    This is also a Jet Drive (I don't know if that is relative)

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    These colors don't run BLWN BUX's Avatar
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    So, if I increase boost to 8-9# and will be running 5600-5800 then I would need about 1350 CFM Carb(s)?

    This Whipple only has one carb flange

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    we're trying to tell you to replace the current carb with a holley 4150 1000cfm or bigger, they make em you better be carefull if that thing is a outdrive and you're gonna increase boost, some outdrive's don't like that

    Dare to be different, if it turns out great you can claim you planned it that way.

    Jetboatperformance.com

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    These colors don't run BLWN BUX's Avatar
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    Its a jet drive with an "A cut" impellar.

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    Senior Member 4CE FED's Avatar
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    Whipple 2.3 or 3.3? ...hope it's not a 2.3 on a 540.
    My 3.3 is a dominator style flange, I think they made either.
    The more I jetted my 1095 demon up, the faster it went, and
    that was only on a stock 502.
    Get an A/F meter first!

    If you have a 3.3 on a 540, I think you will make more power with bigger carb. What's the rest of your fuel system?

    I also know where there is an Accel DFI setup, PM for phone#

  11. #9
    gn7
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    {(cid X rpm)/3456} X {(BOOST/14.7)+1}
    {(540 X 5400)/3456} X {(5/14.7)+1}
    2916000/3456 X .3401 + 1
    843.75 X 1.3041=
    1100.25 You are short, and formula is soft. Anything less, and you are going to have a hard time hitting you boost numbers with the recommended pulleys for that boost. Your choking the blower.



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    Last edited by gn7; 08-24-2009 at 04:45 PM.

  12. #10
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    Quote Originally Posted by 4CE FED View Post
    Whipple 2.3 or 3.3? ...hope it's not a 2.3 on a 540.
    My 3.3 is a dominator style flange, I think they made either.
    The more I jetted my 1095 demon up, the faster it went, and
    that was only on a stock 502.
    Get an A/F meter first!

    If you have a 3.3 on a 540, I think you will make more power with bigger carb. What's the rest of your fuel system?

    I also know where there is an Accel DFI setup, PM for phone#
    I think its a 2.3 (Will have to confirm, boats ate the river storage now)
    I spoke with Whipple today and they said that the 3.3 would say 3300 on the side. I don't recall anything except whipplechaged on mine.

    Whipple told me that I should run a 1050 Dom and can expect about 10# max.

    I would think that I can use a detailed 4150 Carb as recomended by the other guys here.

    I have large fuel lines, and maintain about 9 psi FP under load.
    I have FP guage on dash so monitoring is easy

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    Quote Originally Posted by gn7 View Post
    {(cid X rpm)/3456} X {(BOOST/14.7)+1}
    {(540 X 5400)/3456} X {(5/14.7)+1}
    2916000/3456 X .3401 + 1
    843.75 X 1.3041=
    1100.25 You are short, and formula is soft. Anything less, and you are going to have a hard time hitting you boost numbers with the recommended pulleys for that boost. Your choking the blower.
    Is what i thought also

    TNKS

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    senior member turbo wog's Avatar
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    Quote Originally Posted by BLWN BUX View Post
    Is what i thought also

    TNKS
    i ran a twin turbo with a 850 holley draw through set-up & gained 4mph just by putting on a 1150 dominator i.e. the bigger the straw the easier to suck through, .

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    I've got a 1000cfm annular discharge 4150 on a stock 502/2.3 whipple
    in a 25' warlock cat, has made best of 6lbs @5400/ 96mph gps.
    IMO, you need a bigger carb!

  16. #14
    i'm back!! 1QuickCP's Avatar
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    Yup 4500 dominator for sure...try a 9375 or 9377 ..should work great when dialed in. oh and change linkage to full progressive for much better fuel mileage and drivability

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