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      02-20-2009, 03:26 PM   #1
TBONE1969
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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, 03:28 PM   #2
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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.
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      02-20-2009, 03:36 PM   #3
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Yeah, it totally depends on the cats and how efficient they are.
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      02-20-2009, 03:56 PM   #4
TBONE1969
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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, 04:35 PM   #5
TBONE1969
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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, 05:04 PM   #6
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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, 05:09 PM   #7
TBONE1969
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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, 05:49 PM   #8
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Quote:
Originally Posted by TBONE1969 View Post
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.
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      02-20-2009, 06:21 PM   #9
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The AA 200 cell cats are clear of CEL's

Again, depends how well the exhaust is designed.
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      02-20-2009, 08:09 PM   #10
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Quote:
Originally Posted by sparkyg View Post
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?
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      02-21-2009, 02:54 AM   #11
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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, 04:47 AM   #12
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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, 04:53 AM   #13
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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.
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