downpipe and cbe question
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This is a discussion on downpipe and cbe question within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; So i'm shopping around for a DP and cbe and I have seen all these options, divorced wastegate, secondary 02 ...

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    downpipe and cbe question

    So i'm shopping around for a DP and cbe and I have seen all these options, divorced wastegate, secondary 02 bungs, catless.. so I would like to have 0 issues while installing and afterwards I plan on getting a pro tune with the upgrades, I also don't want to deal with boost creep so i'm leaning towards the catted DP's.

    As far as DP's i'm between the cobb or invidia.

    I know I will buy the Invidia Q300 how loud is it over stock? anyone ever measure the noise levels? I have heard a lot of videos on youtube but its not the same in person.

    The cobb DP i've read tapers to 2.5" does it bolt on to the invidia cbe without problems?

    Also on RSD I only see 1 catted Invidia DP and its divorced wastegate with only 1 02 bung is there a 2 02 bung version if so where do I get it?

    What do you guys recommend/run maybe link a youtube clip of your cars if possible.

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    Master Baiter EJ257's Avatar
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    Invidia has a 1/2 bung version for their downpipes. RSD carries both.

    Considering you want the Q300, if you want the cat closer to the turbo, my advice is to go Invidia; if you want the cat closer to the catback, go TurboXS. Both are full 3" and will mate fine with the Q300.
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    What difference would the cat location make in this case? On the turboXS it seems that theres 2 o2 bungs 1 before the cat and 1 after, I assume a wideband would go before the cat and stock o2 after but its curious all other DP has the wideband bung just after the turbo..

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    Master Baiter EJ257's Avatar
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    Quote Originally Posted by crows
    What difference would the cat location make in this case? On the turboXS it seems that theres 2 o2 bungs 1 before the cat and 1 after, I assume a wideband would go before the cat and stock o2 after but its curious all other DP has the wideband bung just after the turbo..
    That's exactly the case: you want a WBO2 post-turbo / pre-cat.

    A cat closer to the turbo will be more restrictive than one by the catback; a cat closer to the turbo will better prevent boost creep than one by the catback. That said, some cars creep, some don't; a catalyst in the downpipe isn't the proper remedy for that, anyway.
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    Luke Skywalker Mikie13's Avatar
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    Cats? Meh. Go catless (if you're getting a tune other than an OTS one). Get that exhaust-spewing goodness if you're gonna go for it.

    Proven fact, based on countless hours of research: For every catless WRX/STI on the road, you nullify one Prius. Fight the man!
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    Quote Originally Posted by EJ257 View Post
    That's exactly the case: you want a WBO2 post-turbo / pre-cat.

    A cat closer to the turbo will be more restrictive than one by the catback; a cat closer to the turbo will better prevent boost creep than one by the catback. That said, some cars creep, some don't; a catalyst in the downpipe isn't the proper remedy for that, anyway.
    what other mods do I need to prevent the boost creep issues?

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    Registered User wreckingball man's Avatar
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    ^Adjust the WG while getting the car tuned or get better boost control if the problem persists. MBC, EBCS, EWG and tune. A tuner will recognize boost creep and adjust the tune so you hit target boost. Usually not a big deal from what I understand.

    Everything you need to know about boost creep - NASIOC

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    I disagree with your post EJ257, I also was completely sold on the catless dp until i spoke to my tuner (which I know has to do with preference) but just to let you know Precision tuning only tunes with a catted dp for the sole reason that it remedies boost creep. I argued my point by saying that I thought i wouldnt need that much back pressure with all my other mods. They disagreed, so as of now catted dp is on my list. but im still going to try and get more factual support that theyre claim is true. which i highly doubt that it isnt true. but i cant make sense of it

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    So to re-word my original statement, I dont disagree with you EJ. I actually agree with you, but the information given to me by a professional in the business says your statement: "a catalyst in the downpipe isn't the proper remedy for that" is actually wrong.

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    Master Baiter EJ257's Avatar
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    Quote Originally Posted by kdeitrich
    I disagree with your post EJ257, I also was completely sold on the catless dp until i spoke to my tuner (which I know has to do with preference) but just to let you know Precision tuning only tunes with a catted dp for the sole reason that it remedies boost creep. I argued my point by saying that I thought i wouldnt need that much back pressure with all my other mods. They disagreed, so as of now catted dp is on my list. but im still going to try and get more factual support that theyre claim is true. which i highly doubt that it isnt true. but i cant make sense of it
    Quote Originally Posted by kdeitrich
    So to re-word my original statement, I dont disagree with you EJ. I actually agree with you, but the information given to me by a professional in the business says your statement: "a catalyst in the downpipe isn't the proper remedy for that" is actually wrong.
    The issue is when not enough exhaust gas is able to bypass the turbine, causing the turbo to continue building boost. The remedy is allowing more gas to bypass the turbine, either by porting the wastegate or going external.
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    Registered User Ampliified's Avatar
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    Precision tuning in NJ? If so what year car do you have because they were very well known for 02-07 wrx sti not so much for the newer models
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    Luke Skywalker Mikie13's Avatar
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    Quote Originally Posted by kdeitrich View Post
    I disagree with your post EJ257, I also was completely sold on the catless dp until i spoke to my tuner (which I know has to do with preference) but just to let you know Precision tuning only tunes with a catted dp for the sole reason that it remedies boost creep. I argued my point by saying that I thought i wouldnt need that much back pressure with all my other mods. They disagreed, so as of now catted dp is on my list. but im still going to try and get more factual support that theyre claim is true. which i highly doubt that it isnt true. but i cant make sense of it
    "Tuning" for boost creep and using a cat are only bandaid fixes. Boost creep is purely a mechanical issue as EJ stated.

    I'd be more willing to bet that Precision won't tune catless cars because they'd be knowingly putting "illegal" cars back on the road.
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    Quote Originally Posted by Mikie13 View Post
    "Tuning" for boost creep and using a cat are only bandaid fixes. Boost creep is purely a mechanical issue as EJ stated.

    I'd be more willing to bet that Precision won't tune catless cars because they'd be knowingly putting "illegal" cars back on the road.
    Ya I know what u mean, i agree.

    and I have a 2012 wrx Amplified, where did you hear that precision doesnt do the best work on the newer wrxs. its not a sti btw

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    that makes sense EJ, I dont really know boosted cars very well, so dont take offense if i challenge you.im just trying to build my knowledge up a little more so i dont sound clueless. Ive built 2 Datsuns and one jeep wrangler ground up restorations so I know cars decently. The engines were broke down and assembled by hand ...

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    The right way to fix boost creep is to replace the wastegate with one that is properly sized for your application.

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