Replacing downpipe with factory exhaust?
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This is a discussion on Replacing downpipe with factory exhaust? within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; Hi guys, sorry if this is a noobish or annoying question, but I've been searching and can't seem to find ...

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    Replacing downpipe with factory exhaust?

    Hi guys, sorry if this is a noobish or annoying question, but I've been searching and can't seem to find a positive answer. I wan't to run a higher-flow exhaust on my 2014 STI, but, where I live if I do anything to make it louder I'll be pulled over almost daily. I was wondering if anyone has hooked up a COBB (or any other brand really) downpipe to the stock exhaust system? Is it safe for the car, and will it be able to handle more power without replacing the rest of the exhaust? After I figure out what to do with my exhaust I was planning on investing in a front mount intercooler, headers, an up-pipe and fuel pump (I already have a CAI), and just want to find out if this would all be reasonable or safe with only a downpipe. Thanks for any help in advance, and sorry for the noobish question! I wouldn't have asked if I hadn't spent plenty of time searching already!

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    Registered User 360glitch's Avatar
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    Aftermarket down pipe with the factory cat back exhaust system will just be fine. It's recommended that you use a catted down pipe. From what I've personally heard it is no louder than the factory down pipe and will allow you to get that stage 2 power. Just make sure you have your car tuned for the down pipe and/or CAI, as it is unsafe to run them on the factory tune.
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    Registered User A265's Avatar
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    It would also be note worthy that the map notes for the Cobb OTS stage 2 tune on 3g's ask for a full TBE.
    I would get a tune for that CAI if you didn't already, also until you get a big turbo it would be beneficial to keep a TMIC.

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    Registered User xFalleNx's Avatar
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    You're okay to run the DP to the stock catback. I would recommend the Cobb catted DP for that as it's a direct bolt on to the stock cat back.

    What I'm more concerned with is why you want a FMIC, headers, up-pipe, and fuel pump? On a basic stg2 car, none of that is necessary. Do some more research before you mad a mod plan.
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    Quote Originally Posted by xFalleNx View Post
    You're okay to run the DP to the stock catback. I would recommend the Cobb catted DP for that as it's a direct bolt on to the stock cat back.

    What I'm more concerned with is why you want a FMIC, headers, up-pipe, and fuel pump? On a basic stg2 car, none of that is necessary. Do some more research before you mad a mod plan.
    My plan was to follow that up with a bigger turbo and injectors, and take it to considerably a stage 3. I'm still slightly confused on the whole stages and what exactly would be considered each stage, as I've heard slightly different from different sources. Sorry, I'm pretty new to this.

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    Subaru Newb MainFrame's Avatar
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    Forget about stages, you are going to need a custom tune.. personally, I would never run an OTS map even if I was strictly sticking to the map notes.

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    Quote Originally Posted by MainFrame View Post
    Forget about stages, you are going to need a custom tune.. personally, I would never run an OTS map even if I was strictly sticking to the map notes.
    Yes, I was planning on getting a custom pro tune, I just figured stages were more like stages of upgrades?

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    Subaru Newb MainFrame's Avatar
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    Traditionally for Subarus, stage one is a tune on an otherwise stock car, stage two is a tune on a car with an aftermarket downpipe. Some companies have what they call a stage three tune, which mods vary from company to company. Not everyone goes through stages of upgrades.. it's much cheaper in the long run to skip going through stages and just mod the car to how you want it all at once.

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    Registered User A265's Avatar
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    After stage 2, there really is no standard. Vendors consider different things as different stages.

    I personally would hold off with the FMIC until you do the turbo swap, and would only install a FMIC if the turbo is big enough to warrant one.

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    Registered User SUBIE13WRX's Avatar
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    I've been running an invidia catless dp to stock cb for about 2000mi now no problems, made exhaust slightly louder (not much), you stock cb should be fine with those mods correct me if I'm wrong.

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    Registered User SUBIE13WRX's Avatar
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    I'd personally go with pw tmic that's what my next purchess will be,

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    Registered User Ingo's Avatar
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    My 09 has been running a open downpipe into stock muffler for at least 10K Mls, was tuned for it and is just fine. I like the silenced sound, no troubles there.
    You can't have everything - where would you put it?

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    Registered User wreckingball man's Avatar
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    No problem with that. That'd be a good setup if you have crazy cops or strict emissions. I have the exact same setup, now that I do a lot more driving in my car and the sound is very quiet, although im on an 02 wrx so it might not comparable.

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    If you end up with a standard 3 inch downpipe , there Is an adapter to hook into the stock cat back. Not needed but it sure makes for better fitment. I am stage 2 on my sti (invidia catless bellmouth, hks carbon ti & APS 65mm cai) custom tune by mike at Gst motorsports. This tune was done in 2007 (07 sti) making 294awhp 304ft/lb torque

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    Also, you could always use an SPT cat back (which can be ordered from the factory on the car). Keep the brochure regarding spt parts and if you get pulled over,lay it on um!

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