What is the purpose of the secondary cats on the M3?

Pauldramos · 02-26-2012, 07:10 PM

Maybe just go cats back and avoid any problems?

E30M3Brill · 03-23-2016, 08:42 PM

Okay here's a question... in reviving an old thread...

I'm lucky enough to have a lime rock edition with the M-performance mufflers but I would like to add some grunt/rumble. I would not like to mess with throwing O2 sensors errors /deletes - so my thought was to continue to use the primary cats and add on a Challenge Street Pipe - how do you guys think it will sound???

I don't want to go test pipes/ full ipe route because of $$$ and as my car is under warranty til 2021 and would not like voiding anything.

Thoughts, ideas...

BPMSport · 03-23-2016, 11:17 PM

Removing the secondary cats makes it a lot raspier from my experience. They don't play a role in the cat efficiency tests but they do reduce tail pipe emissions. That said, I think you'd still pass with the OEM primaries in place without issue.

Edit. Just realized I replied to this 4 years ago a couple posts up. Sorry for the double post.

E30M3Brill · 03-24-2016, 09:08 PM

Thanks Mike - is there another set of pipes other than the challenge street that retains the primary cats???

BPMSport · 03-24-2016, 11:28 PM

Quote:

Originally Posted by E30M3Brill

Thanks Mike - is there another set of pipes other than the challenge street that retains the primary cats???

It's all one piece, so no matter what you'd have to cut.

02-26-2012, 07:10 PM	#23
Pauldramos 27 Rep 420 Posts Drives: Dinan '11 M3 Join Date: Mar 2011 Location: Solvang, CA iTrader: (1)	Maybe just go cats back and avoid any problems?
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03-23-2016, 08:42 PM	#24
E30M3Brill E90 ZCP 6MT, E92 LimeRock DCT, E30 M3 60 Rep 199 Posts Drives: E30 M3 Join Date: Jun 2015 Location: NY/MA/NC iTrader: (3)	Okay here's a question... in reviving an old thread... I'm lucky enough to have a lime rock edition with the M-performance mufflers but I would like to add some grunt/rumble. I would not like to mess with throwing O2 sensors errors /deletes - so my thought was to continue to use the primary cats and add on a Challenge Street Pipe - how do you guys think it will sound??? I don't want to go test pipes/ full ipe route because of $$$ and as my car is under warranty til 2021 and would not like voiding anything. Thoughts, ideas...
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03-23-2016, 11:17 PM	#25
BPMSport BimmerPost Supporting Vendor 3387 Rep 7,542 Posts Drives: Harrop M3 / F10 M5 / F82 M4 Join Date: Apr 2008 Location: SoCal iTrader: (9) Garage List 2000 BMW M5 [0.00] 1990 BMW 735i Turbo [0.00] 2008 BMW M3 [7.50] 2015 BMW M3 [0.00] 2015 BMW M5 [0.00]	Removing the secondary cats makes it a lot raspier from my experience. They don't play a role in the cat efficiency tests but they do reduce tail pipe emissions. That said, I think you'd still pass with the OEM primaries in place without issue. Edit. Just realized I replied to this 4 years ago a couple posts up. Sorry for the double post. __________________ -----\| Like us on Facebook \| Instagram \|\| Tuning Information \| Remote Coding \|----- ----Visit us at www.BPMSport.com - Emotion. Driven. \| Toll Free: (888) 557-5133----
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03-24-2016, 09:08 PM	#26
E30M3Brill E90 ZCP 6MT, E92 LimeRock DCT, E30 M3 60 Rep 199 Posts Drives: E30 M3 Join Date: Jun 2015 Location: NY/MA/NC iTrader: (3)	Thanks Mike - is there another set of pipes other than the challenge street that retains the primary cats??? __________________ E30 M3 '91 Briliantrot Garage Queen ----- E92 M3 '13 LRP (FO) DCT Stock, w/ only Challenge Mid-Pipe ----- E90 M3 '11 AW 6MT ZCP, Turner Test Pipes, Turner Stage 2 Tune, RAC wheels and other bits...
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