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      10-25-2008, 05:32 PM   #1
ChitownM3
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Rear cat removal....

I did a search and couldn't find any info. I was wondering if the rear cats had any sensors along with them or can they safely be removed without any problems?

Thanks in advance,
Rick
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      10-26-2008, 03:26 AM   #2
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the rear reso's and the mid cats dont have any sensors its okay to play around with them have fun
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      10-26-2008, 12:43 PM   #3
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Quote:
Originally Posted by xxo0oxx View Post
the rear reso's and the mid cats dont have any sensors its okay to play around with them have fun
Excellent, this is what I thought, so I will be removing these come spring time!
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      10-26-2008, 01:13 PM   #4
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Will this have any negative effects on emissions testing?
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      10-26-2008, 01:36 PM   #5
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Quote:
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Will this have any negative effects on emissions testing?
I think all you need s the first set?
I could be wrong
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      10-26-2008, 02:22 PM   #6
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Quote:
Originally Posted by J08M3 View Post
Will this have any negative effects on emissions testing?
Removing catalytic converters will almost certainly not have a positive effect...
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      10-26-2008, 04:16 PM   #7
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If your looking for a little more sound. I would recommend removing the rear resonators. We removed the secondary cats and rear resonators on our E92 M3 and the sound was extremely aggressive and might be too loud for some.

Photo of the OEM exhaust (posted by Greg)


Video of the Eisenmann Race with the rear resonators and Secondary cats removed.
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      10-26-2008, 04:35 PM   #8
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I'm curious about just the second cat being removed on a system with Eisenmann Sport.

Why is there two cats on this system?
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      10-26-2008, 05:00 PM   #9
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1. If I understand correctly the secondary cats are for emissions control during warm-up.

2. Why do you want to remove the secondary cats?

3. A member on this forum had his resonators removed, and he said that it didn't make a big difference in terms of sound (at least with stock mufflers).
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      10-26-2008, 07:22 PM   #10
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1. Does removing BOTH the resonators and the secondary cats require any cutting or can that entire section be bolted off? Can't tell from the pic Nate posted.

2. Why is there a bend in between the secondary cats and the resonators? It doesn't seem like an interference issue since there are supporting brackets bracing the pipes. Are the pipes connected at that point--meaning exhaust flow merges? Is that the reason, to merge flow coming out the two initial cats?

3. If flow is indeed merged in between the secondary cats and resonators at that section of the pipe, what is the effect of running straight pipes down that section as that keeps flow seperate until the muffler(s) (assuming you don't have two disconnected aftermarket mufflers)?
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      10-26-2008, 08:16 PM   #11
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My thoughts on removing the secondary cat if they're not necessary is that they are an unnecessary restriction in the system???
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      10-27-2008, 12:46 AM   #12
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Quote:
Originally Posted by J08M3 View Post
My thoughts on removing the secondary cat if they're not necessary is that they are an unnecessary restriction in the system???
+1

My plan is to remove the secondary cats (gain a couple lost horses), keep the resonator (keep noise levels and rasp low) + Remus Sport mufflers (gain some more power + great sound which will slightly be louder [no secondary cats] but will still be quieter than race mufflers.
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      10-27-2008, 10:16 AM   #13
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Nate
Could u explain furthermore by locating the locations of the 1) resonators 2) primary cats and 3) secondary cats
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      10-27-2008, 03:42 PM   #14
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Quote:
Originally Posted by lucid View Post
1. Does removing BOTH the resonators and the secondary cats require any cutting or can that entire section be bolted off? Can't tell from the pic Nate posted.

+1
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