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      07-07-2015, 05:17 PM   #1
///S55
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Cat delete

Been trying to search but couldn't find any real answers.

To my understanding North American models of the Z4M have 2 cats, 1 right after the headers and the second in the midpipes is that correct?

I am looking to take one out to make the exhaust a little louder.

Anyone have experience with this? And will deleting them throw a CEL?
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      07-07-2015, 05:28 PM   #2
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One set is the headers and the other is in section 1.
I've replaced the section 1 with Rogue catless and passed California smog, sniffer style.
Granted with a lot less margin than before.

There's lots of info on here about every conceivable permutation.

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Last edited by StickMon; 07-07-2015 at 05:33 PM.
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      07-07-2015, 09:28 PM   #3
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All the sensors are in the stock headers, so as far as a CEL is concerned, you're free to do what you want to the s-pipe.
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      07-07-2015, 10:02 PM   #4
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Quote:
Originally Posted by pokeybritches
All the sensors are in the stock headers, so as far as a CEL is concerned, you're free to do what you want to the s-pipe.
Does anyone just delete the secondary cats and result in better sound?
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      07-08-2015, 03:06 AM   #5
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You must not be using the correct terms because this has been discussed many many times. You could do straight pipes by eliminating the secondary cats in section 1. This will make the car more raspy and you will get no CEL.

As far as horsepower it would be better to eliminate the front header cats but that involves way more work. For that you can search euro cats, euro headers, rewiring O2 sensors.
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      07-08-2015, 01:33 PM   #6
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If you want to make more racket without danger of a CEL:

1) Aftermarket mufflers, louder, very little rasp
2) Catless section 1, slightly louder, moderate rasp
3) "Silencer" free X-pipe, bring on the rasp

I declared loud enough after phase 2.
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Last edited by StickMon; 07-09-2015 at 12:48 AM.
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      07-08-2015, 04:51 PM   #7
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Quote:
Originally Posted by StickMon View Post
If you want to make more racket without danger of a CEL:

1) Aftermarket mufflers, louder, very little rasp
2) Catless section 1, slightly louder, moderate rasp
3) "Silencer" free X-pipe, bring on the rasp

A declared loud enough after phase 2.
What is this x-pipe mod that you speak of?
"Catless section 1", does that mean new aftermarket headers?
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      07-08-2015, 05:31 PM   #8
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You really should search the forum.
The system is in 4 parts:
1) Headers, includes primary cats, 4 O2 sensors (fore and aft on each cat) and exhaust gas temp sensor. You don't want to mess with this if you just want to make more racket. It's a pretty deep rabbit hole.
2) "Section 1" a.k.a S-pipes, includes secondary cats. Can be deleted to increase volume and rasp, but will increase HC emissions. I still passed Cali sniffer smog.
3) "X-pipe" a.k.a. cross-pipe, crosses the streams to smooth out pulsations, stock has a "silencer" (pre-muffler) to eliminate rasp. Aftermarket is just 2 pipes that come into one for a couple of inches, then split.
4) Mufflers (cans)

You can have your way with 2-4 without a CEL.

Now see here. Many other brands available.
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      07-08-2015, 06:54 PM   #9
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There's a decent amount of documentation here for Stick's option one as well. I'm about to embark on that endeavor.

It is true that it will yield the greatest performance gains, but it is also the most costly for likely the least amount of sound. However, my catalytic converters in my headers are gone for good (they have failed) so in a way I'm forced into it. I do not believe anyone else has reported such issues here before though. (They're under warranty up to 60k, no year requirement).

The rogue engineering x-pipe that stick posted up is one I can recommend. Truly quality work with a real easy install. I slapped it on without having changed the mufflers, and I have to say I was truly underwhelmed with the outcome. Pair it with a set of cans and it really comes to life. It's quite loud with just an X-Pipe (or section 2) and cans, I've almost grown a little tired of it and I'm still a youngin. But when you get on it... my lord. Too many compliments have I received for the combination currently.

Just another two cents.
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      07-08-2015, 07:59 PM   #10
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Quote:
Originally Posted by StickMon View Post
You really should search the forum.
The system is in 4 parts:
1) Headers, includes primary cats, 4 O2 sensors (fore and aft on each cat) and exhaust gas temp sensor. You don't want to mess with this if you just want to make more racket. It's a pretty deep rabbit hole.
2) "Section 1" a.k.a S-pipes, includes secondary cats. Can be deleted to increase volume and rasp, but will increase HC emissions. I still passed Cali sniffer smog.
3) "X-pipe" a.k.a. cross-pipe, crosses the streams to smooth out pulsations, stock has a "silencer" (pre-muffler) to eliminate rasp. Aftermarket is just 2 pipes that come into one for a couple of inches, then split.
4) Mufflers (cans)

You can have your way with 2-4 without a CEL.

Now see here. Many other brands available.
Thanks!
I can just remove the stock silencers from the X portion and it will end up to be the same setup as the 545.00 option right?
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      07-08-2015, 08:06 PM   #11
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Quote:
Originally Posted by Arsonism View Post
There's a decent amount of documentation here for Stick's option one as well. I'm about to embark on that endeavor.

It is true that it will yield the greatest performance gains, but it is also the most costly for likely the least amount of sound. However, my catalytic converters in my headers are gone for good (they have failed) so in a way I'm forced into it. I do not believe anyone else has reported such issues here before though. (They're under warranty up to 60k, no year requirement).

The rogue engineering x-pipe that stick posted up is one I can recommend. Truly quality work with a real easy install. I slapped it on without having changed the mufflers, and I have to say I was truly underwhelmed with the outcome. Pair it with a set of cans and it really comes to life. It's quite loud with just an X-Pipe (or section 2) and cans, I've almost grown a little tired of it and I'm still a youngin. But when you get on it... my lord. Too many compliments have I received for the combination currently.

Just another two cents.
Thanks for the info man!
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      07-08-2015, 08:17 PM   #12
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Quote:
Originally Posted by ///S54 View Post
Thanks!
I can just remove the stock silencers from the X portion and it will end up to be the same setup as the 545.00 option right?
Were it that easy.
I'm pretty sure it's all welded as one piece.
You could maybe take a sawzall to it.
There are threads on here where peeps have taken a sawzall to the stock mufflers, pulled all the guts out, and welded the cover back together.

Keep an eye on the classified section and you may see a used x-pipe come up for sale.

If you want to make a racket on a budget, here you go:
http://www.zpost.com/forums/showthread.php?t=1102873
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      07-09-2015, 06:20 PM   #13
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Quote:
Originally Posted by StickMon View Post
If you want to make a racket on a budget, here you go:
http://www.zpost.com/forums/showthread.php?t=1102873
I was JUST about to throw this up there. Honestly you could do that and have a shop weld on some different tips. There was another member looking for some options there not too long ago.
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