Downpipe design question - Subaru WRX Forum
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post #1 of 6 Old 08-30-2012, 11:26 PM Thread Starter
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Downpipe design question

Sorry for asking but why does the stock downpipe obliterate the waste hole?

That you ahve to buy aftermarket to have either divorced flow setup or big hole setup?

And final question - do they make a difference?
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post #2 of 6 Old 08-31-2012, 05:18 AM
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Stock DP = inefficiency. I think all automakers do this.

There has always been a debate over divorced and bellmouth downpipes.

I personally have no argument on either. I've always gone with the bellmouth design due to the flow/non restriction.

MAYBE on big turbo setups there may be a slight difference.... But I doubt it. Someone else will chime in, I'm sure.

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post #3 of 6 Old 08-31-2012, 07:46 AM
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One of the biggest problems with the manufacturers of the "divorced" design. They really dont divorce it, just put a plate in there that they say "separates" the gases. Another problem with the "divorced" design that I have read about is; that depending on what turbo you are running the metal tab that is supposed to separate the gases can contact your WG and cause problems there. To solve it you either remove the tab or trim it down. I havent really seen dyno graphs or anything comparing the two. Bellmouth is just more of a guarantee (I believe) for a better and easier fitment/install.

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post #4 of 6 Old 08-31-2012, 09:40 AM
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There are true divorced DP's, just rare and expensive as all H -E double hockey sticks.

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post #5 of 6 Old 08-31-2012, 10:48 AM
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There's nothing wrong with bellmouths. Divorced claims the theoretical high ground but it's smoke and mirrors. Also, most divorced designs are crap in reality, way worse than a standard bellmouth anyway. In theory if you had a big turbo you would benefit from divorced. In practice, big turbos use external wastegates and dump tubes so they are inherently divorced. So to review a bellmouth should be cheaper, harder for the company to screw up, and more than sufficient for any possible application it will be used in.

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post #6 of 6 Old 08-31-2012, 08:23 PM
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I had a bell mouth, and currently have a bosal shorty divorced dp.

i cant tell crap for the difference. get what is cheaper, IMO.

bigger and better than ever
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