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Thread: Building a divided port exhaust manifold help

  1. #1
    Guest nismo's Avatar
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    Building a divided port exhaust manifold help

    Hi, I am building a divided gate manifold for my ca.

    The original manifold pairs the pipes from cylinders 1 and 4 , 2 and 3 before they enter the turbo. I have just seen an aftermarket manifold that pairs 1 and 2 , 2 and 3. Which is best.

    Thanks.

  2. #2
    Dorset & Hants Rep pointz's Avatar
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    Id say 1&4 2&3

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    Guest nismo's Avatar
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    Thanks same as original manifold.

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    The one that pairs 1+2 and 3+4 is junk. (unless it has a pair of parallel twin scroll turbos)

    For an in-line 4 with firing order 1-3-4-2 the exhaust valve is opened on port 4 before the end of the power stroke, while port 3 is open on exhaust stoke, likewise 2-1. The sudden release of pressure from an opened exhaust port can back fill the cylinder that is on exhaust stroke resulting in charge dilution.

    1+4 and 2+3 the exhaust pulses are quite separate and no back flow can occur.

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    Guest ANDY black s13's Avatar
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    These work very well as its a tubular style version of the original unequal length runner design, so some like it will work as good in theory
    https://www.tomeiusa.com/_2003web-ca...nifold_en.html
    the other mani design mentioned with paired runners is probs the french weapon,a rare expensive manifold with thick walled tubes
    they iirc were similar to other equal length designs and some made no power gain till about 4k then made a slight top end gain over the stock mani

  6. #6
    Guest nismo's Avatar
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    Thanks again for the info.

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    Guest polcastrol's Avatar
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    Some pics of the French weapon manifold: http://s1252.photobucket.com/user/po...eshow/Manifold

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