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Old 08-14-2011, 06:04 PM   #1
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Default Adding cat to custom exhaust, looking for advice about placement

I bought the car with a full-back 3" exhaust which had only two resonators in it. I've since replaced one of them with a magna flow straight through muffler, which did tone the sound down somewhat. Now I need to add a cat to pass md state inspection, and I'm left wondering if I should just replace the other resonator with the cat, or add it in addition to the resonator. If I added it, it would have to go behind the resonato, since it's currently sitting just behind the flex pipe that's behind the down pipe, so there's really no other way to go but back. Would this be a problem - as in, would it make the cat less effective for some reason?

Any advice is appreciated.
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Old 08-14-2011, 10:28 PM   #2
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IMO, you should just install it in place of the resonator since it is already downstream of the flex section after the downpipe. The catalytic converter will quiet things down a bit more too, so you can always decide on adding back the resonator if desired.
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Old 08-14-2011, 10:58 PM   #3
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put the cat as realisitically close to the turbo as possible.... that will help it heat up to temp faster
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Old 08-14-2011, 10:59 PM   #4
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Thanks, that's kind of what I was thinking. I'll probably go with replacing the resonator with the cat and see where that puts me.
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Old 08-14-2011, 11:43 PM   #5
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Good luck! Out of curiosity, what does your state inspection consist of? Visual only or sniffer too?
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Old 08-15-2011, 12:35 AM   #6
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Originally Posted by bboyalan View Post
Good luck! Out of curiosity, what does your state inspection consist of? Visual only or sniffer too?
In md, it's visual only for state safety inspection (thorough, but only done once), but the sniff test is done once every two years with emissions insp
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Old 08-16-2011, 05:34 AM   #7
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Ah, I assume that you will go/went in for the emissions inspection then, yes? How were the results btw?
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Old 08-16-2011, 09:25 AM   #8
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Ah, I assume that you will go/went in for the emissions inspection then, yes? How were the results btw?
Not yet. I need to get it state safety inspected to get my title in MD, then once I get that, they make me go in for emissions two months later.

Nah, the guy caught the fact that it was a resonator and that I didn't have a cat. The safety inspection is really tough - it's at least 100 points. The check for the cat during this inspection is for "presence and function", but they don't do the sniff test until the emissions. I know, it makes no sense. In 3 more years I'll be able to qualify for classic car tags though, which is no inspections ever.

Do you think there's a chance that I'll fail the emissions even with the cat on board? It seems like an easy test now since they removed all of the dynos from the emissions facility. They essentially just get in the car and rev it a little bit without loading it up. I figure the car can't be making that much exhaust gas under that condition... Guess they figure it's not worth keeping the dynos when I'm sure at least 95% of their traffic is OBDII port scan only (MY 96+).
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