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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Wed, Jul-07-2010, 03:26:53 AM   #1
Mookster
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Default Cats or no cats?

Howdy all,


My CSL headers came in today and i still havent decide what to do about cats. Emissions arent due for another 18 months so thats not an immediate concern.

How will the car run and sound without cats and what are the drawbacks of not running cats?

Those of you NOT running cats, have you run into any problems?

If i do run cats, it will be CPI's CRT(200 cell).
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Old Wed, Jul-07-2010, 03:38:59 AM   #2
EricSMG
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without any other modifications to the exhaust, the car will sound pretty bad. The rasp is WAY over the top and very very loud. If that's okay with you and you don't mind some fumes once in a while, the car will haul asss
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Old Wed, Jul-07-2010, 03:41:26 AM   #3
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I was in your shoes two weeks ago. I decided to stay cat-less and it is not that bad. I only have stepped headers and everything else is stock it sounds great to me. IF you run cats it would be quieter.

As for the smell I have a convertible it is definitely noticeable but some how it did not bother me enough to want to put cats on. I also do not have a ses light 300 miles + (no tune) so I am planning on staying cat-less.

My only draw back is that I have to clean my exhaust tips more often, which i do at shell every time i pump gas.
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Old Wed, Jul-07-2010, 03:44:55 AM   #4
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Quote:
Originally Posted by EricSMG View Post
without any other modifications to the exhaust, the car will sound pretty bad. The rasp is WAY over the top and very very loud. If that's okay with you and you don't mind some fumes once in a while, the car will haul asss

looks like we got different taste in exhaust note
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Old Wed, Jul-07-2010, 04:10:48 AM   #5
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I have headers with no cats. I am running stock software and no CEL light on ( not sure why CEL not on). There are no problems as I know of at all for running headers with no cats. I even did a Fuel/Air ratio which came out to be a nice straight line with very small variations. It will be a little more noisy but that's about it (I hate that rasp).
Now for the emission problem there is a cat and cat bypass midsection for sale if you want to run both:
http://www.youtube.com/watch?v=6PZCJYvBKac
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Last edited by teoirimia; Wed, Jul-07-2010 at 04:16:35 AM.
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Old Wed, Jul-07-2010, 04:20:11 AM   #6
Mookster
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I guess to clarify some more:

My original setup(in my mind lol)

TMS pulleys
CSL Headers
CPI CRT(200 cell) and rasp terminator(CRT is both rasp terminator and cats)
ESS Tune

but now im thinking of not running cats but running rasp terminator
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Old Wed, Jul-07-2010, 05:30:37 AM   #7
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It's WAYYYYY TOOOOOOO loud catless... maybe I'm getting old but the sound just doesn't sound refined enough for the M3. Then add that gas smell along with the SES light.... When my wallet reloads I'm doing the CP 200 race cats.
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Old Wed, Jul-07-2010, 05:42:13 AM   #8
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Quote:
Originally Posted by ///M3AN ONE View Post
It's WAYYYYY TOOOOOOO loud catless... maybe I'm getting old but the sound just doesn't sound refined enough for the M3. Then add that gas smell along with the SES light.... When my wallet reloads I'm doing the CP 200 race cats.
Really??? Are you running stock exhaust??? If you think that's loud I am running Agency Power exhaust with no cats. There are guys on here that run straight pipes no exhaust. LOL I can't imagine you hearing that then ha?
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Old Wed, Jul-07-2010, 07:20:24 AM   #9
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Quote:
Originally Posted by Mookster View Post
Howdy all,


My CSL headers came in today and i still havent decide what to do about cats. Emissions arent due for another 18 months so thats not an immediate concern.

How will the car run and sound without cats and what are the drawbacks of not running cats?

Those of you NOT running cats, have you run into any problems?

If i do run cats, it will be CPI's CRT(200 cell).

Mook,

If you love rasp, do it! I've ran the w/ and w/o cats. The headers will give you more power no mater what.

I would pick up a set a cats, you dont have to worry about emissions, extra soot, fumes and you'll gain some low end tq..

Ravi
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Old Wed, Jul-07-2010, 09:43:25 AM   #10
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There is no extra power with catless in M3. Even when SC, there is dyno charts proving that it makes more power with euro setup: long headers and cats in s-pipe. So beside the green view, no need for catless unless you don't have the money for it. The sound will be worst catless vs cat system.
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Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)