CEL with high flow primary cat?

TBONE1969 · 02-20-2009, 02:26 PM

I am considering have a shop in LA install a custom header back exhaust on my M3. I am planning on replacing the primary cats with high flow "off-road" cats and replacing the secondary cats with resonators. I have been reading all the threads on this topic, but there are a lot of mixed opinions on whether high flow primary cats will cause the CEL problem. I would rather not have to run new ECU software if I can avoid it! What are the odds of having a CEL?

JuniorDee · 02-20-2009, 02:28 PM

it depends on the cell count of the cats. I would say you would be safe with a 300 count and maybe even a 200 count, but no way with a 100 count.

FStop7 · 02-20-2009, 02:36 PM

Yeah, it totally depends on the cats and how efficient they are.

TBONE1969 · 02-20-2009, 02:56 PM

They are a good quality 400 count cat, but they are short. The core is only 3" long.

TBONE1969 · 02-20-2009, 03:35 PM

I had them on my '04 Audi S4 and I had no CEL problems. I am unsure if BMWs are more sensative!

Sticky · 02-20-2009, 04:04 PM

400 cell cats SHOULD be fine, but no way to say 100% for sure until you find it out yourself. I can say 100% for sure software will turn it off. Plus, a CEL is not really that big of a deal.

TBONE1969 · 02-20-2009, 04:09 PM

Does a CEL have any effect on performance (i.e. limp mode) or is it only the annoyance of having the CEL lit up on the dash?

Sticky · 02-20-2009, 04:49 PM

Quote:

Originally Posted by TBONE1969

Does a CEL have any effect on performance (i.e. limp mode) or is it only the annoyance of having the CEL lit up on the dash?

Just annoying.

sparkyg · 02-20-2009, 05:21 PM

The AA 200 cell cats are clear of CEL's

Again, depends how well the exhaust is designed.

mixja · 02-20-2009, 07:09 PM

Quote:

Originally Posted by sparkyg

The AA 200 cell cats are clear of CEL's

Again, depends how well the exhaust is designed.

I thought the AA's were 300 cell?

Jonmartin · 02-21-2009, 01:54 AM

I think my car is a freak lol my car went 1200 miles with no CEL after i chopped my front cats and then it wasn't until I drove up in the Higher elevations to go snowboarding that the CEL came on. I dynoed with it on and after I left the CEL went away and hasn't come back since..

BimmerRob08 · 02-21-2009, 03:47 AM

What is CEL exactly? I'm assuming some kind of engine check light or code for something to do with the ECU and an error code. Any definitions?

FStop7 · 02-21-2009, 03:53 AM

Check
Engine
Light

It pops up when there is a notable fault in the fuel/ignition/exhaust/electronics etc.

Removing the cats throws a code and causes a CEL but it has no adverse impact on performance.

02-20-2009, 02:26 PM	#1
TBONE1969 Private 15 Rep 97 Posts Drives: AW '18 340i Join Date: Feb 2009 Location: Santa Cruz iTrader: (1)	CEL with high flow primary cat? I am considering have a shop in LA install a custom header back exhaust on my M3. I am planning on replacing the primary cats with high flow "off-road" cats and replacing the secondary cats with resonators. I have been reading all the threads on this topic, but there are a lot of mixed opinions on whether high flow primary cats will cause the CEL problem. I would rather not have to run new ECU software if I can avoid it! What are the odds of having a CEL?
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02-20-2009, 02:28 PM	#2
JuniorDee Captain 73 Rep 610 Posts Drives: the speed limit Join Date: Apr 2007 Location: the land of brat and brotchen iTrader: (1)	it depends on the cell count of the cats. I would say you would be safe with a 300 count and maybe even a 200 count, but no way with a 100 count. __________________ EDC.....viagra for your car
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02-20-2009, 02:36 PM	#3
FStop7 I like cars 329 Rep 5,052 Posts Drives: M6 Join Date: Oct 2008 Location: Newbury Park, CA iTrader: (3)	Yeah, it totally depends on the cats and how efficient they are. __________________ My photostream: http://www.flickr.com/photos/racelap/
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02-20-2009, 02:56 PM	#4
TBONE1969 Private 15 Rep 97 Posts Drives: AW '18 340i Join Date: Feb 2009 Location: Santa Cruz iTrader: (1)	They are a good quality 400 count cat, but they are short. The core is only 3" long.
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02-20-2009, 03:35 PM	#5
TBONE1969 Private 15 Rep 97 Posts Drives: AW '18 340i Join Date: Feb 2009 Location: Santa Cruz iTrader: (1)	I had them on my '04 Audi S4 and I had no CEL problems. I am unsure if BMWs are more sensative!
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02-20-2009, 04:04 PM	#6
Sticky Banned 78 Rep 2,244 Posts Drives: E92 Jerez DCT M3 Join Date: Jan 2008 Location: Anaheim Hills / Malibu iTrader: (0)	400 cell cats SHOULD be fine, but no way to say 100% for sure until you find it out yourself. I can say 100% for sure software will turn it off. Plus, a CEL is not really that big of a deal.
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02-20-2009, 04:09 PM	#7
TBONE1969 Private 15 Rep 97 Posts Drives: AW '18 340i Join Date: Feb 2009 Location: Santa Cruz iTrader: (1)	Does a CEL have any effect on performance (i.e. limp mode) or is it only the annoyance of having the CEL lit up on the dash?
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02-20-2009, 05:21 PM	#9
sparkyg Brigadier General 142 Rep 3,523 Posts Drives: A6 Allroad Join Date: Sep 2007 Location: Oil Country iTrader: (5)	The AA 200 cell cats are clear of CEL's Again, depends how well the exhaust is designed.
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02-21-2009, 01:54 AM	#11
Jonmartin Banned 121 Rep 2,097 Posts Drives: E90 M3 Join Date: Nov 2005 Location: Los Angles (818) iTrader: (1)	I think my car is a freak lol my car went 1200 miles with no CEL after i chopped my front cats and then it wasn't until I drove up in the Higher elevations to go snowboarding that the CEL came on. I dynoed with it on and after I left the CEL went away and hasn't come back since..
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02-21-2009, 03:47 AM	#12
BimmerRob08 Major 110 Rep 1,311 Posts Drives: 2008 M3, Space Gray Join Date: Mar 2008 Location: KIKR (ABQ), NM iTrader: (0)	What is CEL exactly? I'm assuming some kind of engine check light or code for something to do with the ECU and an error code. Any definitions?
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02-21-2009, 03:53 AM	#13
FStop7 I like cars 329 Rep 5,052 Posts Drives: M6 Join Date: Oct 2008 Location: Newbury Park, CA iTrader: (3)	Check Engine Light It pops up when there is a notable fault in the fuel/ignition/exhaust/electronics etc. Removing the cats throws a code and causes a CEL but it has no adverse impact on performance. __________________ My photostream: http://www.flickr.com/photos/racelap/
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