General Miata Chat A place to talk about anything Miata

Adding cat to custom exhaust, looking for advice about placement

Thread Tools
 
Search this Thread
 
Old 08-14-2011, 05:04 PM
  #1  
Newb
Thread Starter
 
Neon01's Avatar
 
Join Date: Jul 2011
Location: Forest Hill, MD
Posts: 27
Total Cats: 0
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.
Neon01 is offline  
Old 08-14-2011, 09:28 PM
  #2  
Newb
iTrader: (2)
 
bboyalan's Avatar
 
Join Date: Jul 2011
Location: Chula Vista SD
Posts: 44
Total Cats: 0
Default

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.
bboyalan is offline  
Old 08-14-2011, 09:58 PM
  #3  
Senior Member
iTrader: (8)
 
aaronc7's Avatar
 
Join Date: Jun 2010
Location: Florida
Posts: 1,116
Total Cats: 43
Default

put the cat as realisitically close to the turbo as possible.... that will help it heat up to temp faster
aaronc7 is offline  
Old 08-14-2011, 09:59 PM
  #4  
Newb
Thread Starter
 
Neon01's Avatar
 
Join Date: Jul 2011
Location: Forest Hill, MD
Posts: 27
Total Cats: 0
Default

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.
Neon01 is offline  
Old 08-14-2011, 10:43 PM
  #5  
Newb
iTrader: (2)
 
bboyalan's Avatar
 
Join Date: Jul 2011
Location: Chula Vista SD
Posts: 44
Total Cats: 0
Default

Good luck! Out of curiosity, what does your state inspection consist of? Visual only or sniffer too?
bboyalan is offline  
Old 08-14-2011, 11:35 PM
  #6  
Newb
Thread Starter
 
Neon01's Avatar
 
Join Date: Jul 2011
Location: Forest Hill, MD
Posts: 27
Total Cats: 0
Default

Originally Posted by bboyalan
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
Neon01 is offline  
Old 08-16-2011, 04:34 AM
  #7  
Newb
iTrader: (2)
 
bboyalan's Avatar
 
Join Date: Jul 2011
Location: Chula Vista SD
Posts: 44
Total Cats: 0
Default

Ah, I assume that you will go/went in for the emissions inspection then, yes? How were the results btw?
bboyalan is offline  
Old 08-16-2011, 08:25 AM
  #8  
Newb
Thread Starter
 
Neon01's Avatar
 
Join Date: Jul 2011
Location: Forest Hill, MD
Posts: 27
Total Cats: 0
Default

Originally Posted by bboyalan
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+).
Neon01 is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Full_Tilt_Boogie
Build Threads
84
04-12-2021 04:21 PM
StratoBlue1109
Miata parts for sale/trade
21
09-30-2018 01:09 PM
Corky Bell
Prefabbed Turbo Kits
18
11-22-2016 09:01 PM
Goldwar
DIY Turbo Discussion
2
09-29-2015 09:20 AM



Quick Reply: Adding cat to custom exhaust, looking for advice about placement



All times are GMT -4. The time now is 04:48 AM.