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Old 04-15-2009, 02:53 PM   #1
subadub07
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Default 2.5i. # of cats? 1?

The last time i was under there i noticed one. Is there another one? It's raining now or I'd check.
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Old 04-15-2009, 02:55 PM   #2
n/a boxer
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Actually the correct answer is 2,409... nah jk I think its like 4... someone correct me I know I'm wrong
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Old 04-15-2009, 03:00 PM   #3
VIsubi
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its 2 but one is your resonator which looks like your cat its a bit flatter than your cat and its right before your T/C or a lil bit after..
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Old 04-15-2009, 03:11 PM   #4
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there is one main cat, which is built into the factory UL header (look at your o2 sensor locations), the second one is more like a resinator then a cat and can be removed.
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Old 04-15-2009, 04:35 PM   #5
formula91
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I like cats, but I'm allergic to them.

That's why I have an 05RS instead.



Seriously though I think there's only one cat, or at least only one that should matter if you're thinking about emissions.
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Old 04-15-2009, 05:12 PM   #6
dstan
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on the older RS we have 2 but are very visible with all the heat shields
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Old 04-15-2009, 06:06 PM   #7
2.5i
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Holy wrong information batman, the 06-07 2.5is have one cat in the header, another in the in the cat pipe right after the header, then you have a resonator and finnally the muffler.

Total Cats: 2
Total Resonators: 1
Total Mufflers: 1

Oh I know this because I removed them.
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Old 04-15-2009, 07:03 PM   #8
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Quote:
Originally Posted by 2.5i View Post
Holy wrong information batman, the 06-07 2.5is have one cat in the header, another in the in the cat pipe right after the header, then you have a resonator and finnally the muffler.

Total Cats: 2
Total Resonators: 1
Total Mufflers: 1

Oh I know this because I removed them.

I can confirm this as I am intimately familiar with my exhaust as it was from the factory and now. The first cat is near the end of the exhaust manifold (header). there is an O2 sensor just before and one just after the cat in the exhaust manifold. there is a second cat close behind the first, but located in the "catpipe", so the two cats are separated by a couple flanges with a gasket between them. the second cat is for emission reasons but is not monitored by any O2 sensors (unlike the first cat) so modifying/gutting/removing it will have no effect on the ECU or cause any CEL's.

The resonator is located in the "midpipe" which is the third section of the exhaust and this section of the exhaust has a two spring-loaded bolts to connect it to the catpipe on the front flange and just a regular gasket with bolts on the rear flange. The resonator is large and oddly shaped compared to the cats, so it's not easily confused for a cat.

Hope that makes it clear and cut&dry so the OP is not confused by the first few less than ideal answers in this thread.

The 08/09 should be similar design with different shaped pipes after the exhaust manifold (header).
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Old 04-17-2009, 09:35 PM   #9
2.5i
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Quote:
Originally Posted by RaceFaceXC View Post
the second cat is for emission reasons but is not monitored by any O2 sensors (unlike the first cat) so modifying/gutting/removing it will have no effect on the ECU or cause any CEL's.
This is very true, but its makes it loud as **** if you don't have a muffler after it... I may or may not be doing this right now.
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Old 04-17-2009, 11:09 PM   #10
Vizzionz
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Quote:
Originally Posted by 2.5i View Post
Holy wrong information batman, the 06-07 2.5is have one cat in the header, another in the in the cat pipe right after the header, then you have a resonator and finnally the muffler.

Total Cats: 2
Total Resonators: 1
Total Mufflers: 1

Oh I know this because I removed them.
Actually it's only 1 cat (which the ECU reads), the 2nd supposed cat is just mearly a resinator.. [this is information directly from a subaru tech @ a local dealer]

i removed both of them on my 2.5i.. and i'm STILL passing "fair" on the emissions testing that they have set up on the side of the roads in Denver!
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Old 04-19-2009, 02:38 PM   #11
GrundleJuice
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Quote:
Originally Posted by 2.5i View Post
This is very true, but its makes it loud as **** if you don't have a muffler after it... I may or may not be doing this right now.
no muffler will make just about anything loud as ****.


Quote:
Originally Posted by Vizzionz View Post
Actually it's only 1 cat (which the ECU reads), the 2nd supposed cat is just mearly a resinator.. [this is information directly from a subaru tech @ a local dealer]

i removed both of them on my 2.5i.. and i'm STILL passing "fair" on the emissions testing that they have set up on the side of the roads in Denver!
That tech is wrong. I dismanteled the 2nd cat and it was, indeed, a cat. fur, claws and the whole bit. but seriously, its a catalytic converter. There are much better designs for controlling sound than the shape that they use for the cats. Also, putting a resonator that close to the heads is just asking for trouble in terms of how long it lasts. That's why mufflers (muffler=resonator) are always right before the exhaust exits the vehicle.
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