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Old 03-07-2013, 04:16 PM   #1
jnewell
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Default 06' STI Setup Help

I'm a complete newb when it comes time to Subaru. I just bought my 06 STI on Saturday 3/2/13. It has what seems to be installed from the dealer at initial delivery an SPT cat back exhaust and SPT intake. I am wondering if it is worth while to replace the SPT cat back with a full turbo back exhaust or should I find a down pipe and call it a day. My second concern is I have no clue if the previous owner had tuned it or not. With my research it seems COBB stage 1 map will be safe but if I want to go stage 2 I should get a turbo back exhaust. Has anyone ran into this same situation and with those of you that are more knowledgeable can you provide some incite?
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Old 03-07-2013, 04:22 PM   #2
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Originally Posted by jnewell View Post
I'm a complete newb when it comes time to Subaru. I just bought my 06 STI on Saturday 3/2/13. It has what seems to be installed from the dealer at initial delivery an SPT cat back exhaust and SPT intake. I am wondering if it is worth while to replace the SPT cat back with a full turbo back exhaust or should I find a down pipe and call it a day. My second concern is I have no clue if the previous owner had tuned it or not. With my research it seems COBB stage 1 map will be safe but if I want to go stage 2 I should get a turbo back exhaust. Has anyone ran into this same situation and with those of you that are more knowledgeable can you provide some incite?
Personally, I would keep the SPT catback and get a downpipe. I really like quieter, lower-key, clean looking, authentic exhaust systems which is why SPT is great. A Cobb downpipe would go beautifully with that. With the SPT exhaust, all you will need to go Stage 2 is a downpipe, you do not need a different cat-back, unless you want a more conspicuous and louder exhaust but power output would increase very minimally, if any. Nothing that you will ever feel.
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Old 03-07-2013, 04:28 PM   #3
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Personally, I would keep the SPT catback and get a downpipe. I really like quieter, lower-key, clean looking, authentic exhaust systems which is why SPT is great. A Cobb downpipe would go beautifully with that. With the SPT exhaust, all you will need to go Stage 2 is a downpipe, you do not need a different cat-back, unless you want a more conspicuous and louder exhaust but power output would increase very minimally, if any. Nothing that you will ever feel.
I agree I like the sound of the SPT exhaust its not too loud and looks great. I just don't wanna run into issues getting them to mate up. From what I have read the SPT cb is 3" but goes down to 2.25 at the mate to the stock down pipe. Would it just be a waste of time if I got a 3" dp just to bottle up to 2.25 at the mate with the SPT cb.
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Old 03-07-2013, 05:36 PM   #4
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You would be stage 1, if you add a downpipe you will be stage 2. A downpipe+ a catback is a turboback, doesn't matter what company combination you have. If you should "change it" depends on if you like the sound of it, or another brand.
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Old 03-07-2013, 05:48 PM   #5
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My first step is going to be order a COBB AP and flash to stage 1. Then get the COBB down pipe and reflash to stage 2. I'm thinking with my research this of course is the best bet then it will be on to coilovers.
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Old 03-07-2013, 06:05 PM   #6
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I agree I like the sound of the SPT exhaust its not too loud and looks great. I just don't wanna run into issues getting them to mate up. From what I have read the SPT cb is 3" but goes down to 2.25 at the mate to the stock down pipe. Would it just be a waste of time if I got a 3" dp just to bottle up to 2.25 at the mate with the SPT cb.
A Cobb downpipe will fit perfectly. The Cobb downpipe tapers from 3" to 2.5" I believe. Correct me someone if I'm wrong, but it does taper down.
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Old 03-07-2013, 08:27 PM   #7
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Yes it does taper. That's why I didn't get it haha
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Old 03-07-2013, 09:22 PM   #8
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Yes it does taper. That's why I didn't get it haha
That's what I was thinking because it sounds crazy to have a 3" dp and 3" cb that meet at 2.5" but I've heard that its good for back pressure. Idk...
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Old 03-07-2013, 10:54 PM   #9
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Any DP that connects to a stock CB (which is most all of them) will taper at the connection to the CB, it is the only way to make it work.
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Old 03-08-2013, 03:00 AM   #10
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Any DP that connects to a stock CB (which is most all of them) will taper at the connection to the CB, it is the only way to make it work.
Wrong.
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Old 03-08-2013, 07:29 AM   #11
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Wrong.
What do you suggest? I'd like to avoid that bottle neck if possible. I've heard of people going to a shop and having them cut and weld a 3" pipe from one to the other but idk if I agree or am willing to even consider that.
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Old 03-08-2013, 07:33 AM   #12
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Looking at most turbo back systems they seem to taper down to 2.5 also. Just sounds like they are trying to make the parts universal to both a stock and aftermarket solution.
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Old 03-08-2013, 08:31 AM   #13
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Honestly, unless your going to go for a big turbo/built motor set-up, you're not going to feel a power increase on an exhaust that doesn't taper. It really will make very little difference.
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Old 03-08-2013, 08:42 AM   #14
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Wrong.
How can any DP that connects to the stock CB donut gasket be any size other then stock at that point?

I could see if the DP did not use the stock donut gasket. If that was the case, how would it connect to the stock CB?
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Old 03-08-2013, 12:25 PM   #15
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The flanges are the same size on after market dp and stock cb. Thats how it fits. To the OP if the taper bothers you get a 3" dp. There are many options out there that don't taper. Cobb has really nice products as long as you have the cash. You can get quality and spend less on a 3" dp. Also IMO unless your tracking the car your money can be spent better elswhere on the car than coil overs.
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Old 03-08-2013, 12:54 PM   #16
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Quality is what I care about. I wouldn't buy a cheaper product just for the sake of a half inch in my stock turbo STi. If I were in your situation I would purchase a Cobb down pipe and go Stage 2 with the Accessport. Done. But that's just me. I'm a bit too picky when it comes to quality. You are talking to someone who spent 3 hours picking dog hair out of my carpet with a pair of tweezers after I bought my 24k mile 11' WRX. Is that weird?
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Old 03-08-2013, 03:02 PM   #17
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Quality is what I care about. I wouldn't buy a cheaper product just for the sake of a half inch in my stock turbo STi. If I were in your situation I would purchase a Cobb down pipe and go Stage 2 with the Accessport. Done. But that's just me. I'm a bit too picky when it comes to quality. You are talking to someone who spent 3 hours picking dog hair out of my carpet with a pair of tweezers after I bought my 24k mile 11' WRX. Is that weird?
I'm the same way and I think I've determined that's what I'm going to do.
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Old 03-08-2013, 10:08 PM   #18
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The flanges are the same size on after market dp and stock cb. Thats how it fits.
The stock donut gasket is 2.5" inner diameter, therefore any DP that uses the stock donut gasket to connect to the CB will be 2.5" at that point, regardless of the size of the flange. Can a DP connect with a 3" diameter flat gasket, sure. But you will have an exhaust leak if the CB flange is designed for a donut gasket, not a flat gasket. Grimmspeed sells an adapter to go from a 3" flat gasket DP to a donut gasket CB, of course it is 2.5" diameter as a result.




To the OP, I agree with you about quality. I think it is far more important than the very minimal effect the 2.5" diameter portion of the DP has. Cobb designed in a properly tapered transition from 3" to 2.5" to accomdate the stock CB style connection, it will not be an issue.

Your SPT CB has a 2.5" donut gasket connection to the DP. Any DP you get will need to have the same connection or you will need an adapter, like the one Grimmspeed sells. If you get rid of the SPT CB and replace it with a CB that does not use the donut gasket then you can get a "full 3" DP". If you keep the SPT CB, you will have a 2.5" diameter connection between the DP and CB regardless of the size of the DP.
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Old 03-08-2013, 10:40 PM   #19
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Originally Posted by jebjkey View Post

The stock donut gasket is 2.5" inner diameter, therefore any DP that uses the stock donut gasket to connect to the CB will be 2.5" at that point, regardless of the size of the flange. Can a DP connect with a 3" diameter flat gasket, sure. But you will have an exhaust leak if the CB flange is designed for a donut gasket, not a flat gasket. Grimmspeed sells an adapter to go from a 3" flat gasket DP to a donut gasket CB, of course it is 2.5" diameter as a result.

To the OP, I agree with you about quality. I think it is far more important than the very minimal effect the 2.5" diameter portion of the DP has. Cobb designed in a properly tapered transition from 3" to 2.5" to accomdate the stock CB style connection, it will not be an issue.

Your SPT CB has a 2.5" donut gasket connection to the DP. Any DP you get will need to have the same connection or you will need an adapter, like the one Grimmspeed sells. If you get rid of the SPT CB and replace it with a CB that does not use the donut gasket then you can get a "full 3" DP". If you keep the SPT CB, you will have a 2.5" diameter connection between the DP and CB regardless of the size of the DP.
Thanks man I really appreciate the advice!!!
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Old 03-08-2013, 11:07 PM   #20
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Where do you live specifically? I know every Subaru owner and Subaru parts vendor within 900 miles of Virginia and would rather set you up with locals whom you can punch in the face for bad advice than people on the internet whom you cannot punch.
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Old 03-09-2013, 06:39 AM   #21
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Yes I finally got a hold of my tuner
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Old 03-09-2013, 06:40 AM   #22
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Yes I finally got a hold of my tuner

Last edited by Unabomber; 03-09-2013 at 06:46 PM.
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Old 03-09-2013, 08:42 AM   #23
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Originally Posted by Unabomber View Post
Where do you live specifically? I known almost every Subaru owner and Subaru parts vendor within 900 miles of Virginia and would rather set you up with locals whom you can punch in the face for bad advice than people on the internet whom you cannot punch.
Corrected for accuracy.

~818 miles
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Old 03-09-2013, 01:47 PM   #24
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Where do you live specifically? I know every Subaru owner and Subaru parts vendor within 900 miles of Virginia and would rather set you up with locals whom you can punch in the face for bad advice than people on the internet whom you cannot punch.
I live right in Richmond.
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Old 03-09-2013, 02:34 PM   #25
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Originally Posted by Unabomber View Post
Where do you live specifically? I know every Subaru owner and Subaru parts vendor within 900 miles of Virginia and would rather set you up with locals whom you can punch in the face for bad advice than people on the internet whom you cannot punch.
Sounds like you are very knowledgeable. What do you think about the Cobb downpipe SPT intake and SPT catback with the Cobb accessport stage 2 map? Or anyone that has seen or is knowledgeable about this similar setup.
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