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  1. #1
    Closed mouth no get fed,...... travelboysteve's Avatar
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    3" vs 4" air intake,........

    Hopefully this will not get into a pissing match, but my question is this,.......if the intake on the supercharger is only, what 2.5 inches in diameter, then what is the REAL benefit of using a 4 inch intake over a 3 inch intake. I understand colder air compresses differently, better, etc. BUT, if both tubes are extracting air from the same place, ie: 3 OR a 4 inch rear intake, or internal front compartment intake, I just don't get why a 4 inch would produce any really noticable gains as it will eventually be reduced down to the size of the SC anyway,.....I'd like to know what the race junkies, gurus, etc. can elaborate about this,....

    Hell, I had a random thought that since my 3 inch sucks from the front compartment, if I stuck a bag of ice in the port just above the seat, I should get colder air, thus increased hp's. (Higher rate of compressed cool air, right?)
    In real life i know this to be nothing more than a great idea on how to get ice cubes sucked into your engine,.... so I won't try it.


  2. #2
    H2HO's Avatar
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    try an ice pack

  3. #3
    Moderator Franko's Avatar
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    First, I "think" a bigger diameter intake hose works better because it brings more air at the beginning of the hose, not at the SC. Kind of like a funnel, the beginning is big to accomodate more flow. This is only my theory and may be wrong, but I know from personal experience that a 4" hose adds about 1 psi over a 3" hose.

    Second, cooling the air before the IC will not do that much good. Of course it helps to suck cooler air, but the air coming in gets heated by the SC compressing the air. The IC then cools it (only by the temp of the ambient water). So the the main cooling needs to occur after the air goes through the SC.

    Be advised that I am not a mechanic or otherwise qualified to render the opinions set forth above. But I did stay at a Holiday Inn Express last night.

  4. #4
    H2HO's Avatar
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    Quote Originally Posted by Franko View Post

    But I did stay at a Holiday Inn Express last night.
    Are you serious?

  5. #5
    Moderator Franko's Avatar
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    Quote Originally Posted by sstaino View Post
    Are you serious?
    That's a good point you make. I was lying. So disregard all of the foregoing.

  6. #6
    H2HO's Avatar
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    Thanks for pointing that out.

  7. #7
    Prohibido usuario
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    The sc compresses the air and the more air readily available the better. The reason boost goes up is because more air is available to compress. If there was ZERO friction then the intake hose could be the same size as the sc opening. There is friction though and the loss of available air is made up by the larger intake hose.

  8. #8
    Closed mouth no get fed,...... travelboysteve's Avatar
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    Quote Originally Posted by Franko View Post
    First, I "think" a bigger diameter intake hose works better because it brings more air at the beginning of the hose, not at the SC. Kind of like a funnel, the beginning is big to accomodate more flow. This is only my theory and may be wrong, but I know from personal experience that a 4" hose adds about 1 psi over a 3" hose.

    Second, cooling the air before the IC will not do that much good. Of course it helps to suck cooler air, but the air coming in gets heated by the SC compressing the air. The IC then cools it (only by the temp of the ambient water). So the the main cooling needs to occur after the air goes through the SC.

    Be advised that I am not a mechanic or otherwise qualified to render the opinions set forth above. But I did stay at a Holiday Inn Express last night.
    Thanks Franko, you gave me an idea,......I'll install an ice chest in line with my IC and cool the water that way,......... no seriously, thanks guys,......I often wondered that, OK, for another question, same topic. There are small plugs available for quads and MX bikes that allow more airflow to the air box, shown below, similar to the 2 inch ones available for PWC's, are there any available with the foam screens that you guys know of? is it a help or just wishful thinking? I'm trying to figure out a way to allow cooler air into the intake, even though after compression it'll warm some, wondering if adding cooler air would be a benefit as for my quad and truck,........
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  9. #9

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    I'm breathing only fresh, outside air in my intake setup, and I have so far been disappointed with the results. My first 4" intake, even breathing hot engine air, was such an improvement over stock, I surmised that taking in air that's a good 50 degrees cooler should make a big difference, but it didn't. Wasn't any worse, but doesn't seem any better either. Maybe the SC is going to heat the air up to some temperature, no matter what the initial temp is? Maybe we're faster in the winter because the water going through the IC is cooler, not because the air outside is that much cooler?

  10. #10
    ou812's Avatar
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    Quote Originally Posted by VX1 View Post
    Maybe we're faster in the winter because the water going through the IC is cooler, not because the air outside is that much cooler?
    Both.

    Try rigging up an ice pack/pocket on top, below or around the Ext. IC unit & pack it with dry ice. Nice ice cold air there!

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