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DC Crew
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Discussion Starter #1
Holy Restriction Batman!

Sure, the EPA will hate you, or fine you. It's your call.

But, why are we spending $900 on an exhaust system when the real GROWL and flow happen when you gut your catalytic converters?

You want to see what's between your exhaust maniforld and your cat back exhaust system.

Talk about restriction!!!!

All the debree you see is from ONE CATALYTIC CONVERTER on my GS.

The car has been driven 700 miles since the gutting and the car has NOT thrown any codes.

Gutting...



More gutting... (yes, that pile is from ONE cat)



Even more gutting... (yes, that pile is from ONE cat)



Your passenger side cat...



To get at the guts, you have to cut the passenger one and then re-weld it, the drivers side you can do it while it's on the car.



Passenger side cat...



Emptied driver side cat. Have a shop vac handy after you shatter all the stuff inside. And DO NOT breath this stuff in.



Why get an aftermarket exhaust when THIS is the power-robbing restriction!!!
 

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Black 08, A&A TI supercharger. Kooks headers. CCW wheels. Much more
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i did that a year ago.i also got code's after driving and had to install o2 simulator's,i'm sure you will have to do the same.the good thing is if some one look's,there still there.you can say,"i'm not the origanal owner,i alway's thought the exhaust was stock."

but the fella's that get the sniffer test,probably would fail the test badly.most place's have some sort of smog testing....
 

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DC Crew
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Discussion Starter #3
hawaii-5-lo said:
i did that a year ago.i also got code's after driving and had to install o2 simulator's,i'm sure you will have to do the same.


Put about 200 miles on the car, no codes at all. :excited:
 

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DC PIT CREW BOSS
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Aren't the O2 sensors located upstream of the cat?
 

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How does it sound now Patrick?
I put on 2 Borla's a couple of years ago and hardly noticed any sound increase. I removed the 2 pre cats and tried again, WHALA!
Big differance in sound and performance. Like a totally different car!:thumbsup:
 

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Torch Red 2K said:
Aren't the O2 sensors located upstream of the cat?
there's one in front,and one behind the cat.on both pipe's.that's how the computer know's there hollow,or when there clogged.
weird how some car's get code's and other's don't.i only have two cat's,the later c5s have four cat's....meow...
 

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DC Crew
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hawaii-5-lo said:
but the fella's that get the sniffer test,probably would fail the test badly.most place's have some sort of smog testing....
Our cars get the anal probe test here. Dallas has a lot of pollution (smog). Constant ozone warnings in the summer. I choose to blame it on the amount of hairspray that escapes into the atmosphere. :D
 

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:laughing: hair-spray...

if i had to have the sniffer test,i would put some random tech cat's on,i would not try to get into trouble.
no-smog test's here,and my convertor's are actually "in place",i'm not breakin the law.:thumbsup:
 

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I dont have any cats!:lookinup: Unfortunatly for me I have to go through emissions soon so I will be getting a set of random tech free flow ones. Patrick arnt you a little nervous that someone will read this thread that shouldent....epa,mvd etc....?:huh:
 

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DC Crew
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Discussion Starter #12
Magic Man said:
How does it sound now Patrick?
I put on 2 Borla's a couple of years ago and hardly noticed any sound increase. I removed the 2 pre cats and tried again, WHALA!
Big differance in sound and performance. Like a totally different car!:thumbsup:
BAD ASS GROWL! Thick and crackly. It demands authority and respect on the street!
 

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resident conservative
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Soon the Feds will crack down on states the dont do emission checks. The new techology is road side checks that are non evasive, it checks you on drive by, they radio the cop car ahead, then site you for emission failure ticket
Sometimes techology sucks!!:(
 

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DC Crew
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Discussion Starter #14
84 GRANDSPORT said:
I dont have any cats!:lookinup: Unfortunatly for me I have to go through emissions soon so I will be getting a set of random tech free flow ones. Patrick arnt you a little nervous that someone will read this thread that shouldent....epa,mvd etc....?:huh:
Jesus. How much more trouble could I POSSIBLY be in right now? :laughing:
 

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Hey patrick thats pretty awesome you havent thrown any codes yet! i am very seriously considering gutting my cats! That sure was a hell of a lot of junk in there! how many miles do you have on your car? if i remember right its a lot lower compared to mine! i htink i have close to if not over the amount of miles you do! i should really look into gutting mine! who knows what they look like now!
 

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i have to say im impressed that you havent thrown a code yet. I am sure it sounds awesome even with stock manifolds but i have a couple questions. Did you cut off the cats with a hacksaw and then reweld them yourself? what did you use to gut them? is the old broomstick method doable? I dont think a muffler shop will take off cats for you id you done cut them off yourself although they may weld them abck on for you if you already had them cut off and gutted. how is backpressure? it does look like it was extremely clogged but i would be afraid of losing to much back pressure without an Xpipe.
 

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O2 sensors with gutted CATs

If you 96 and newer, OBDII guys are thinking of gutting your cats, here's some more info for you:

ODBII cars have two O2 sensors per side (one in front of the cat, 1 behind it). You will want to put a resistive O2 sensor simulator in place of the REAR sensor after you remove or gut your cats. The data from the forward sensor is very important because it is used by the PCM to help regulate the air/fuel ratio for performance and economy. The sensor after the cat tells the computer if the car's tuning is in accordance with CARB (California Air Research Board)'s emissions standards.

Many states, including AZ where I live, don't do a tailpipe sniff on ODBII cars, they simply plug into the OBDII port and check for PCM codes. If your car has no codes, they give you a pass and send you on your way. If your state does do tailpipe sniffs, and your car's engine is tight, and the fuel and all your filters are clean your car may STILL pass. the CAT is not as vital to reducing emissions on an ODBII car as they were on older, less sophisticated PCM systems

Also, if you plan to do this mod, then the best thing to do after gutting your cats is to modify them by lopping the ends off and running a pipe that's the same diameter as the rest of your exhaust straight through them, leaving the external casing as camouflage in case your state does visual inspections. Leaving the hollow casings in place is OK, but it still creates some turbulence and back pressure in your exhaust flow. A stright pipe running through them ensures smooth exhaust flow. This. of course, can only be done if you are a do-it-yourselfer. No exhaust shop is going to perform any of these mods for you.
 

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DC Crew
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Discussion Starter #19
1996man said:
Hey patrick thats pretty awesome you havent thrown any codes yet! i am very seriously considering gutting my cats! That sure was a hell of a lot of junk in there! how many miles do you have on your car? if i remember right its a lot lower compared to mine! i htink i have close to if not over the amount of miles you do! i should really look into gutting mine! who knows what they look like now!
No codes at all.

But, I can now spin the tires on the 2-3 shift @ 85 MPH.

I'm telling you, gut the cats and change your fuel filter, you won't be disappointed.

:thumbsup:
 

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DC Crew
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Discussion Starter #20
Originally posted by 1996man

Did you cut off the cats with a hacksaw and then reweld them yourself?


Nope, my buddy cut them with a saws-all and then welded them back up nice and perty.

what did you use to gut them? is the old broomstick method doable?[/b]
Anything we could find. But found that a BIG ASS screwdriver with a small sledge hammer shattered most of it, then you scrape the sides. Easy, really.

I dont think a muffler shop will take off cats for you id you done cut them off yourself although they may weld them abck on for you if you already had them cut off and gutted. how is backpressure? it does look like it was extremely clogged but i would be afraid of losing to much back pressure without an Xpipe. [/B]
You don't want back pressure in a 96. I have heard repeatedly that gutting the cats get's you 20HP, period. It's a major restriction.

Like I said, my car now spins the tires on the 2-3 shift, and goes sideways on the 1-2. Crazy **** man.
 
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