Secondary Cats and Emissions?

RocketBoots · 02-02-2015, 12:11 AM

For systems, like the Akra Evo, Eisenmann, that replace the midpipe and secondary cats, do they effect emissions so that the car would fail smog?

///M Villain · 02-02-2015, 01:03 AM

From what I've been told, no. The secondary cat's can be removed from the stock exhaust as well. The data for emissions is coming from the downpipes.

irablumberg · 02-02-2015, 10:30 AM

From what we have seen of stock and aftermarket exhausts, there are no O2 sensors behind the secondary cats. Thus, removing them will not cause a CEL. However, the real question is can the car pass a tail pipe sniffer test without these cats and if so, does the engine need to be fully warmed up?

I believe that the purpose of secondary cats is additional exhaust filtering for times when the primary cats are not up to full operating temperature and thus are not working at full efficiency.

Anyone know?

LukasAT · 02-02-2015, 10:42 AM

Quote:

Originally Posted by irablumberg

From what we have seen of stock and aftermarket exhausts, there are no O2 sensors behind the secondary cats. Thus, removing them will not cause a CEL. However, the real question is can the car pass a tail pipe sniffer test without these cats and if so, does the engine need to be fully warmed up?

I believe that the purpose of secondary cats is additional exhaust filtering for times when the primary cats are not up to full operating temperature and thus are not working at full efficiency.

Anyone know?

I would also like to know that. In VA we have to do emissions test and will you pass that without 2nd cats?

agentrnge · 01-18-2019, 05:24 PM

Bumping this old post. Also looking for this info. Love the sound the AA midpipes to get rid of rasp, but that deletes the secondary cat. Any confirmation/source its for warm up only? How important is it for emissions? No CELs?

ThatSquirrelPoweredE90 · 01-20-2019, 05:32 PM

For Californians like myself, we're pretty screwed. When our models show up on their computer, it will state that there are 4 catalytic converters for the car. It will also give a vague description on where the cats are located on the car.(2 on exhaust manifold and 2 under the car) Now taking the gamble of how lenient your smog shop is, they may see a red flag when they only count two cats. Your car will pass the computer, but not the visual. But again, it can really depend on your smog shop.

Fun side story

When I was trying to smog my 2010 335i, I forgot I had a JB+ that was connected to the MAF sensor. I mean, you really had to dig into the car with a mirror to find it, but the guy doing my smog found it and failed me LOL

He also mentioned I should take off my metal charge pipe since it wasn't stock(like that has to do with emissions

) Quickly took off the JB+ and went to another shop right after and passed

02-02-2015, 12:11 AM	#1
RocketBoots Colonel 1860 Rep 2,104 Posts Drives: Horse Drawn Carriage Join Date: Jan 2014 Location: Bay Area iTrader: (3)	Secondary Cats and Emissions? For systems, like the Akra Evo, Eisenmann, that replace the midpipe and secondary cats, do they effect emissions so that the car would fail smog?
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02-02-2015, 01:03 AM	#2
///M Villain Second Lieutenant 91 Rep 258 Posts Drives: Bmw M4 Join Date: Jul 2014 Location: Atlanta, Ga. iTrader: (1)	From what I've been told, no. The secondary cat's can be removed from the stock exhaust as well. The data for emissions is coming from the downpipes.
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02-02-2015, 10:30 AM	#3
irablumberg Lieutenant 239 Rep 407 Posts Drives: 2021 M5 Competition Join Date: Jul 2014 Location: Portland, OR iTrader: (0)	From what we have seen of stock and aftermarket exhausts, there are no O2 sensors behind the secondary cats. Thus, removing them will not cause a CEL. However, the real question is can the car pass a tail pipe sniffer test without these cats and if so, does the engine need to be fully warmed up? I believe that the purpose of secondary cats is additional exhaust filtering for times when the primary cats are not up to full operating temperature and thus are not working at full efficiency. Anyone know?
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01-18-2019, 05:24 PM	#5
agentrnge Lieutenant 382 Rep 487 Posts Drives: 2018 M3 6MT, 2001 740iL Join Date: Dec 2014 Location: Morris County, NJ iTrader: (0)	Bumping this old post. Also looking for this info. Love the sound the AA midpipes to get rid of rasp, but that deletes the secondary cat. Any confirmation/source its for warm up only? How important is it for emissions? No CELs?
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01-20-2019, 05:32 PM	#6
ThatSquirrelPoweredE90 Private First Class 121 Rep 128 Posts Drives: '15 i3 REx, '02 4Runner Join Date: Dec 2015 Location: Orange County, California iTrader: (0)	For Californians like myself, we're pretty screwed. When our models show up on their computer, it will state that there are 4 catalytic converters for the car. It will also give a vague description on where the cats are located on the car.(2 on exhaust manifold and 2 under the car) Now taking the gamble of how lenient your smog shop is, they may see a red flag when they only count two cats. Your car will pass the computer, but not the visual. But again, it can really depend on your smog shop. Fun side story When I was trying to smog my 2010 335i, I forgot I had a JB+ that was connected to the MAF sensor. I mean, you really had to dig into the car with a mirror to find it, but the guy doing my smog found it and failed me LOL He also mentioned I should take off my metal charge pipe since it wasn't stock(like that has to do with emissions ) Quickly took off the JB+ and went to another shop right after and passed
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