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Catalytic Converter Question

1941Galant

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Aug 21, 2004
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Charles Town, WV
I am currently running a 3" exhaust w/ no muffler and no cat. The car still has an 05 inspection sticker, so I need to throw both a muffler and cat on it before I take it in, not to mention I want to quiet the car down some. Now here is what I was thinking. I have enough room to install my 3" magnaflow and a highflow cat at the end of the exhaust between where the exhaust currently ends, and where the muffler would sit, and I would use a v-band clamp to attach the muffler/cat to the rest of the exhaust so I can easily pop it off and throw a downturn on for when I go to the track.

My question is, will my exhaust get hot enough towards the back to allow the cat to function properly? From the little bit of research that I have done (http://www.aa1car.com/library/converter.htm), the cat needs to be between 400 and 600 degrees to start functioning properly. Is there anything else I should be concerned about with doing this?
 

1941Galant

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Aug 21, 2004
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Charles Town, WV
I forgot to say that I would rather not pull the exhaust off and install a cat in the middle. I don't want to deal with crawling under it to switch to a test pipe everytime I go to the track.
 

ktmrider

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Sep 10, 2007
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3,128
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Tempe, AZ
You already covered the question, the cat efficiency will degrade the further you place it from the exhaust manifold.
Also not knowing your local/state regulations, specifically if there is a visual on OBD-I cars, you could fail by not having it in a stock-type location.
 

atc250r

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Sep 11, 2003
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Orange County, NY
Do they do a sniffer where you are or just a visual?

John
 

CP

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Aug 30, 2004
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West Simsbury, CT
^^^Then why would you care about cat efficiency? If they don't sniff your exhaust, you could put a gutted cat on there and pass.
 

1941Galant

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Aug 21, 2004
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Charles Town, WV
The reasons I wanted to put an actual cat on are that I already have one sitting in my basement, and it would help quiet the car down. I don't really care about efficiency, but if I did put a cat on the car I would want it to actually work, or else I would go a different route. Now I am considering just saying screw it and pulling the exhaust to install a fake cat and maybe a resonator.
 

atc250r

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Sep 11, 2003
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Orange County, NY
Look around online, you can buy cat shields somewhere. I bought a set years ago on DSMTrader. You just put them over the pipe, weld them together, then weld them to the pipe and it looks like you have a cat. You could also try installing a resonator where the cat should be and telling the mechanic that its a high flow cat.

John
 

1941Galant

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Aug 21, 2004
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Charles Town, WV
That is a good idea John, I tried doing a quick search for just the shields but couldn't come up with much, I'll hit it again tomorrow after class. However, I did find a fake cat for $40 through siliconeintakes.com, so that is always an option.
 

Struc

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Nov 24, 2008
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764
Location
Oconomowoc, WI
I have a prototype (I believe Magnaflow) resonator that looks just like a cat on my Spyder. They never did make it (my guess because of legal issues), but I can't imagine it would be too hard to duplicate.
 

G

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Feb 24, 2004
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zompton

atc250r

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Sep 11, 2003
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Orange County, NY
A modern cat isn't a big restriction. Problems start when the engine starts running too rich or too lean and fouls the cat, then you're stuck buying a new one. I'd spend the $40 for a fake one, by the time you find the shields and have them welded on you'll save money by going with a fake. I still think most mechanics will let a car with a resonator where the cat should be slip through.

John
 

1941Galant

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Aug 21, 2004
Messages
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Charles Town, WV
Thats a good point. The car is running pretty rich right now since I only have a keydiver chip, which aside from running rich, the car runs great. A buddy of mine will help me out with getting the exhaust taken care of, so I think I am just going to go with a fake cat, then put the muffler at the end. If it is still too loud I will look at adding a resonator.
 
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