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3x3 mod: Why so big?

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Since the opening on the carb is only about 3.5 sq.in., what makes more than that beneficial? I understand why the bell mouth tapers in on the carb itself to speed up the air and mix it with the fuel better. The filter and rubber boot seem like they'd cancel any beneficial flow characteristics prior to the bell mouth. I did search the forums until my eyes could take no more :ride: so if there's already an explanation, I'd appreciate being pointed that way. I did read Eddie's comment about sticking with 3x3 to keep everybody on the same sheet of music, but that was all I could find.👍

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The narrower diameter inside the carb called the Venturi is to create a low pressure, not to speed up the air, although that is part of the effect.

VenturiFlow.png

See how the liquid at the left side is about twice as high as the right side? The same volume of air is flowing through both parts, but the smaller diameter is a faster flow and lower pressure causing the liquid to rise - the same thing happens in the carb with gasoline.

Also, you don't want the intake tract to be perfectly smooth, otherwise the fuel would fall out of suspension.

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