HP vs CFM basic question
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HP vs CFM basic question

  1. #1
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    Default HP vs CFM basic question

    SO........ I am told there is a basic factor for what CFM carb flow you need per HP. It is something like 1.67 CFM/HP. The question is, this may be so for a 4 stroke V-8 but what about say a 2.0 liter 2 stroke? Save the bantering please. Thanks - Franky

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    Senior Member H20MOFO's Avatar
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    I think you could google one up (carb cfm calculator) I think it's more like plug in, C.I.D. max rpms, and volummetric(sp) eficency.
    Another Hot Boat refugee

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    Senior Member stix818's Avatar
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    If you can find virtual engine calculator it will do it for you along with many other things!! If you send me your email I can attempt to get it to you. Let me know
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    Doing math for the 300 Franky?
    Keith-


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    Quote Originally Posted by STV_Keith View Post
    Doing math for the 300 Franky?

    yeah, those whiney ass big block guys.....like 15 minutes was not enough they have to throw in the "if you want to use the good block (which I was already building) you have to use an obscure, hard to find tiney ass carb" It is like having a 454 with a two barrel....

    Geez, who makes this sh*t up?

    Rant over

    By the way, all my other boats have big blocks, two blown. This is my first outboard in 16 years.

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    Quote Originally Posted by stix818 View Post
    If you can find virtual engine calculator it will do it for you along with many other things!! If you send me your email I can attempt to get it to you. Let me know
    Thanks that would be great. What about the 2-stroke factor? I PM'd my e-mail

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    Quote Originally Posted by franky View Post
    By the way, all my other boats have big blocks, two blown. This is my first outboard in 16 years.
    The outboard guys don't know the answer ? It's my understanding that it is real hard to overcarb a two-stroke. Is this a high HP engine or a cruiser and what rpm range are you looking to run it ?

    I'll ask a couple of my "smart" friends tomorrow.

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    Senior Member STV_Keith's Avatar
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    Quote Originally Posted by franky View Post
    By the way, all my other boats have big blocks, two blown. This is my first outboard in 16 years.
    You mean besides the STV?
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    Quote Originally Posted by STV_Keith View Post
    You mean besides the STV?
    Forgot about that one, didn't have it very long.

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    Senior Member stix818's Avatar
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    I'm not sure about the 2 stroke thing but I did send it to you. It's pretty interesting can even figure out your credit card payment!!
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    cfm
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    I'd talk to the 2 stroke guru's since they are hard to understand for the 4cycle guys like me. I own 2 stroke's (snowmobile's) but I don't understand them near enough to do what I do with 4 strokes.

    Remember, a 2 stroke pulls in air/fuel, combusts, exhausts every rotation of the crank vs every other like a 4 stroke.

    Just the fact that they use the exhaust as an intake supply too, just completely freakin baffles me. LOL.

    See pic:
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    Last edited by cfm; 06-10-2008 at 10:34 AM.

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