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Thread: Air intake pipe smaller diameter

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    Air intake pipe smaller diameter

    Can anyone explain me why they use such a small diameter of air intake pipe on this carb engine?

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    Re: Air intake pipe smaller diameter

    its still huge compared to the venturi in the carb, and at only 45bhp it doesn't exactly need a lot of air

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    Re: Air intake pipe smaller diameter

    Quote Originally Posted by Graham View Post
    its still huge compared to the venturi in the carb, and at only 45bhp it doesn't exactly need a lot of air
    Agreed and if its much bigger than a single inlet valve max. opening area its effectively oversized.

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    Re: Air intake pipe smaller diameter

    Is there any advantage why they go from a small diameter to a bigger one? I would guess air speed slows down when diameter increases?

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    Re: Air intake pipe smaller diameter

    As air speed goes down air pressure increases - its hardly measurable but does occur which does help in the carb. As when it flows through the venturi, the constriction increases the speed and so lowers the pressure giving better draw on the jets. If its dropping from a higher number, it works better!

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    Re: Air intake pipe smaller diameter

    After the inlet tube there is a large plenum/filter area so the air speed would get changed greatly by that so I doubt in a filtered air situation that the size of the inlet tube would make any difference to the carb. I cannot think of any other reason for making the inlet so small though other than maybe it helps to air to flow around and through the filter better somehow?
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    Re: Air intake pipe smaller diameter

    for the OE manufacturer noise was probably also consideration

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