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post #1 of 105 (permalink) Old 12-31-2008, 03:31 PM Thread Starter
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STI exhaust

I know all this has been covered before, but it is scattered all over the place I'll try to consolidate it into one thread. One, the exhaust may or may not need to be extended. It will either be about 2" short or 1/4" short, the latter does not need an extension added and some even think the first doesn't either. Two, the FXT hangers are about 1.5" center to center. So you either need to use the Kartboy XL hangers (realize they will transfer more sound to the cabin compared to rubber) or any generic hanger that is roughly 2.75"-3" in length (this will give about a .75" gap between the tip and bumper so no concerns about the bumper melting). I found some at Autozone for $4, but after removing the midpipe the hanger is about the right length and probably could be used on the rear. If you go with a generic hanger then realize you will have to ream out the holes since they will be too small to fit the Subaru ones. The other option here is to heat and bend the hanger arms on the muffler up about 1.5" and use the stock/shorter hangers. Three, I replaced the midpipe as well as the axleback and it has a nice deep bass burble from idle to 1500 RPM's, after that is basically just as loud as the FXT cat-back (no highway drone). Finally this is EXTREMELY easy to do and if you are hesitant go ahead and do it, you'll love the sound (just right, loud in all the right places). The rear hangers are your biggest concern, the exhaust doesn't sit any lower than stock it tucks up rather nice. If you bend the hanger arms you will have less lateral movement compared to the longer hangers. Hope all this helps narrow things down. Please post any questions about the install and I or someone will be more than happy to help. Now get out there and put this on already!

Update:
So I put on a Turboxs AB today and measured the STI midpipe, and just as I remembered it was exactly the same length as the FXT.

...........................FXT.............STI
Tip:....................6 5/8"..........7 1/4"
Muffler:..............17 1/8"........16 1/2"
Overall length:.....46 1/2"........46 1/4"
midpipe...............49 3/4"........49 3/4"

Again these measurements are from a 2004 FXT and 2006 STI.

2004 FXT A/T (vf43 08 STI TMIC)

Last edited by scubadoober; 04-13-2011 at 04:47 PM.
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post #2 of 105 (permalink) Old 12-31-2008, 07:05 PM
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I see a lot of people running this exhaust with a downpipe like say Cobb. I was wondering what the diameter of the sti exhaust was and it takes to mount up to a downpipe. also does it restrict much flow? can you still run AP stage 2 with this setup?

96 STI Type RA Coupe
05 FXT 5MT AW
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post #3 of 105 (permalink) Old 12-31-2008, 07:40 PM
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Quote:
Originally Posted by fxt05 View Post
I see a lot of people running this exhaust with a downpipe like say Cobb. I was wondering what the diameter of the sti exhaust was and it takes to mount up to a downpipe. also does it restrict much flow? can you still run AP stage 2 with this setup?
Very good questions.

STi TBE Diameter: 2.5"

--The only difference in dia. between the STi and our stock FXT tbe exhaust is that the axleback tapers slightly right before the muffler to 2.25".

--The only difference in a STi tbe and our stock FXT tbe is the above mentioned, muffler, tip and the midpipe. The midpipe has a smaller resonator that will give you a big more burble compared to the stock midpipe.

Having said this, most aftermarket downpipes are 3", so you'll need a 2.5"-3" adapter to run the rest, STi.

3" is always better for flow and hp, but a bunch of people run the STi because it's very quiet and not as restrictive as the stock FXT muffler.

Yes, it's completely safe to run a Stg.2 map with a STi catback or axleback. You'll just be out a few ponies compared to an aftermarket 3" catback or axleback.

Last edited by subisan; 01-01-2009 at 08:44 AM.
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post #4 of 105 (permalink) Old 01-01-2009, 07:45 AM Thread Starter
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Quote:
Having said this, most aftermarket (Cobb) downpipes are 3", so you'll need a 2.5"-3" adapter to run the rest, STi.
Well sorta, the Cobb is a 3" DP but it has the factory style doughnut flange. This allows it to bolt right up to the stock exhaust, but it also has to taper to 2.5" to do so.

2004 FXT A/T (vf43 08 STI TMIC)
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post #5 of 105 (permalink) Old 01-01-2009, 07:51 AM
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the length of the STi cat-back is about the same as the XT, but if you were to just use the axle-back, it's shorter.

also, if you're going to use the cheaper, generic rubber hangers from Pep Boys or AutoZone, just know they DO NOT last long. about half a year later, my pops shook the STi cat-back on his XT, and one of the hangers tore. lol

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post #6 of 105 (permalink) Old 01-01-2009, 08:45 AM
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Quote:
Originally Posted by scubadoober View Post
Well sorta, the Cobb is a 3" DP but it has the factory style doughnut flange. This allows it to bolt right up to the stock exhaust, but it also has to taper to 2.5" to do so.
Thanks, I edited my original post.
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post #7 of 105 (permalink) Old 01-02-2009, 11:18 AM Thread Starter
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Quote:
the length of the STi cat-back is about the same as the XT, but if you were to just use the axle-back, it's shorter.
Well I had heard this as well, but after I installed mine it seemed to be in basically the same location as the original. So I decided to measure the two and see what the actual differences were. During my install I laid the two midpipes side by side and they were the same length, so I immediately thought well that dispels the rumor that the missing length is in the midpipe. So I measured the axlebacks and was a bit surprised.
...........................FXT.............STI
Tip:....................6 5/8"..........7 1/4"
Muffler:..............17 1/8"........16 1/2"
Overall length:.....46 1/2"........46 1/4"

While the overall length of the STI axleback was measured on the car and the FXT was measured off, they were measured in the same manner and from the same points (tape from the flange parallel to the muffler with a straight edge perpendicular to the tape). This is an 06 STI catback on an 04 FXT, I cannot guarantee that these measurements would apply to other years. So this reinforced my observation of it being in about the same spot, at worst my measurements could be off by 1/8" but I measured a half dozen times on both to be sure. So as stated above I see no reason to lengthen this exhaust if there is only a 1/4" difference.

2004 FXT A/T (vf43 08 STI TMIC)

Last edited by scubadoober; 01-02-2009 at 12:52 PM.
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post #8 of 105 (permalink) Old 01-02-2009, 11:42 AM
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^
i didn't go by rumor, i took pictures of them side-by-side when i did the install for my pops. i was working with an 05MY XT and an 07MY STi. when i get the time, i'll try to dig up those pictures. i thought i had posted them on here at that time. but when we did the axle-back first, it was short. so, we ended up doing the full cat-back.

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Last edited by tallazzPilipino; 01-02-2009 at 11:48 AM.
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post #9 of 105 (permalink) Old 01-02-2009, 11:51 AM
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It almost seems like there are slight variations in the axleback depending on MY, possibly for both the FXT and STi. I used an STi axleback only, and like scubadoober mine sits in almost exactly the right spot. Canonshooter had the same experience.

I know other people have had to lengthen the axleback by up to 2", so there has to be some differences somewhere.

Also wanted to throw in that a few of us have used XL hangers from Napa, part number 35719. No need to open the hole up, they fit the same as stock. Only issue is that the Napa hangers are just a little bit longer than necessary (longer than the Kartboy XLs) so the tip sits lower than stock (not a ton but you can tell). This can be a good thing if you have a hitch, though.

'07 FSXT WRB protuned VF39
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post #10 of 105 (permalink) Old 01-02-2009, 11:54 AM Thread Starter
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I was simply posting my observations, and in no way discounting any other members experiences. I was just as confused to see the measurements after seeing member after member after member saying it was considerably shorter (aside from smooth906 and canonshooter, man you guys post quick). I'm in no way saying that everyone else is wrong, since I seem to be the only one that has posted this result. I would be interested in seeing your pics though.

2004 FXT A/T (vf43 08 STI TMIC)

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post #11 of 105 (permalink) Old 01-02-2009, 12:06 PM
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i guess i did post those pictures. not the ones from the side though.

05MY XT + 07MY STi ehxuast

it may be hard from those pictures at that angle, but from other pictures i had (and if you were actually looking at those two exhausts side-by-side from their actual sides, you could definitely see the difference in lengths.


Quote:
Originally Posted by scubadoober View Post
I was simply posting my observations, and in no way discounting any other members experiences. I was just as confused to see the measurements after seeing member after member after member saying it was considerably shorter (aside from smooth906 and canonshooter, man you guys post quick). I'm in no way saying that everyone else is wrong, since I seem to be the only one that has posted this result. I would be interested in seeing your pics though.
^
your observations are definitely worth posting. we should all know what's what, and know where the differences lay. i, also, remember someone on here selling an STi axle-back mentioning it was extended the 2" it was originally missing.

we're going to get the 05MY XT cat-back fitted to my brother's 01MY SF. i'll try to catch a measurement of it before they cut it up for welding.

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Last edited by tallazzPilipino; 01-02-2009 at 12:13 PM.
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post #12 of 105 (permalink) Old 01-02-2009, 12:16 PM Thread Starter
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^^^Man it was you, you don't know how long I've been looking for that thread. It's just kinda hard to tell from the pics, if you say it's longer I believe you but there has to be some differences in STI/FXT combinations to give such different results.

2004 FXT A/T (vf43 08 STI TMIC)
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post #13 of 105 (permalink) Old 01-02-2009, 12:18 PM
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^
yeah, in those pictures, it looks close to even. but, i remember seeing the difference when looking from the side. also, the flanges on one cat-back was on the ground while the flanges from the other cat-back were up in the air a bit.

i'm guessing the difference is in the mid-pipe. do you know the length of your XT mid-pipe?

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post #14 of 105 (permalink) Old 01-02-2009, 12:33 PM Thread Starter
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Quote:
and if you were actually looking at those two exhausts side-by-side from their actual sides, you could definitely see the difference in lengths.
This might have something to do with the FXT muffler being about 5/8" longer, I would think those measurements are the same. So I guess the question is which STI exhaust gives this 2" difference or where does the rear flange sit compared to the heatshield that is connected to the under carriage? After double checking my STI catback is off an 06 STI, I edited my previous post.

2004 FXT A/T (vf43 08 STI TMIC)

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post #15 of 105 (permalink) Old 01-09-2009, 04:29 PM
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So, anyone run an 05 STI catback on an 04XT? (I assume midpipe and axleback = catback?)

Looking to do one man!!!!! Just want to know if anyone has experience and whether I'll need to extend it. I'm REALLY hoping not to! I'm having the seller measure the axleback, and then with the midpipe, and I'll measure mine to compare so I'll know.

Since this is to be THE thread for STI exhaust usage, thought I'd ask!

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