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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > OBD II Compliant State Emissions Testing and the 335i Exhaust System



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      05-14-2013, 11:36 AM   #23
carlsontheflyer
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Originally Posted by falconey View Post
I'm in Atlanta and I had zero issues passing an emissions test with the downpipe fix. Inspector didn't even look at the cats, but you shouldn't be failed if you keep the secondary cats which aren't deleted with catless downpipes anyway.
The EPA rule book says that primary cats must be present. The secondary cats are too far downstream to heat up enough to initiate the proper chemical reaction. In other words, they are not enough to burn off the remaining HC, CO and NOx gases. The vehicles that only have one cat or dual cats downstream rely heavily on the EGR system, which in those cases is much more prone to failure as it gets clogged up with carbon buildup.

Of course, many, if not most emission inspectors are ignorant of the fact that some cars have primary and secondary cats, or what cats looks like, for that matter. They will often glance under your car with the aid of a mirror on a broomhandle, see the resonators and assume those are the cats, and you get a pass.

Next time come to my station for emission test. I wont open your hood.
I'm in Alpharetta / Johns Creek area.
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      05-14-2013, 12:52 PM   #24
falconey
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Originally Posted by carlsontheflyer View Post
The EPA rule book says that primary cats must be present. The secondary cats are too far downstream to heat up enough to initiate the proper chemical reaction. In other words, they are not enough to burn off the remaining HC, CO and NOx gases. The vehicles that only have one cat or dual cats downstream rely heavily on the EGR system, which in those cases is much more prone to failure as it gets clogged up with carbon buildup.

Of course, many, if not most emission inspectors are ignorant of the fact that some cars have primary and secondary cats, or what cats looks like, for that matter. They will often glance under your car with the aid of a mirror on a broomhandle, see the resonators and assume those are the cats, and you get a pass.

Next time come to my station for emission test. I wont open your hood.
I'm in Alpharetta / Johns Creek area.
Cool, I live off of Nesbit Ferry. Moving soon though. I think the key is the knowledge part of this. Most inspectors don't even know all the tricks to get around what the computer reads, let alone what stock parts come with the car, so if the computer says 'pass', they just roll with it.
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      05-18-2013, 07:10 PM   #25
fistofsouth
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So after conducting some research apparently there is not a custom exhaust/ muffler shop in DFW that can make mandrel bends. That being the case I guess I'm back to buying a pre-built cat-back.

Is the AFE 2.75 inch cat-back the largest diameter cat-back made?

If it is then I guess my best option is to get the Ar Designs catted DPs, which are a full 3 inches up until the flange, then have the muffler shop cut off the flange on the DP and then fashion a stainless steel transition to the 2'75 inch aFe cat-back, giving me at leas 2.75 inches throughout the system. Ultimately I just want the system that reduces back pressure by the maximum amount.

Last edited by fistofsouth; 05-18-2013 at 10:54 PM.
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