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Old 02-04-2007, 10:11 PM   #1
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DIY: Gutting out your Catalytic Converter

If you suddenly experience a loss of power at around 4K rpm and your car just refused to go, there is a very good chance the your CAT is gone.
I had just spent a week trying to figure out what was wrong with my car, just to find that the reason for it all was a burned cat.

This DIY is for those of you, who always thought of getting a catless midpipe, but never got their hands to do it and waited long enough until their cat has finally failed, or whatever the reason it might be that you want to run your car catless.

Here is a clean and simple way of doing it, without spending any money.

1. Take off your cat.
Taking it off is very straightforward.
All you neet is to disconnect the oxygen sensor from the connector jst above it.
Unscrew three 14mm nuts on the front joint, two 14mm nuts on the back joint, detach the 2 horizontal support panels by unbolting 12 mm bolts that hold them in place (4 in each) and finally pulling off the rubber mount.
Even after you take off everything that holds your cat, the pipe will remain in place. To get it off grab a large screwdriver (carefully not to damage the metal ring in there) jam it between the flanges on the front join and using the screwdriver as a lever separate the joint. Once it is out, Just pull the whole pipe out of the rear joint.

2. Take out the Oxygen sensor:
Remove the sensor guard by unscrewing two 10mm nuts.
Unscrew and remove the sensor.

2. Gutting your cat.
Get a 11/2-2 foot long half 1/2" steel rod or something similar ( Home depot for about a buck ) and a hammer.
Flip the pipe vertically with the front (triangular flange facing up)
stick the rod inside the cat opening and using the hammer keep on whacking the internals until the rod breaks through. The is made of 2 parts, meaning that there are actually 2 elements inside that pipe, so when you break the first one, shake the pieces out, and continue whacking on it and shaking stuff out until there is nothing left. Use a light to see inside to make sure that it is empty. When everything is out, you'll see that the inside walls of that (now just resonator) are relatively clear and there is nothing left.

This is it. Now you are a proud owner of a completely stock looking catless midpipe
Reinstall the sensor, and put everything back following the directions above in reverse.
Happy modding.

P.S
The dual structure of the cat is actually the reason the car looses power when the damn thing burns out. When the cat goes, the debris from the front part of the converter (which takes most of the abuse) completely clogs up the second portion of it, and blocks that exhaust flow.
Your engine simply can't breathe and so it starts to loose power more and more, and if you continue on pushing it, the cat will eventually clog completely, causing the engine to just shut off.
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Old 02-06-2007, 07:32 AM   #2
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you right about it,i've done it last year but lack of words to wrote it anyway good write up for DIY
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Old 02-06-2007, 07:43 AM   #3
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Does this have any affect on the performance at all I know some car need so much back pressure. Also wouldn't you fail a emission test?
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Old 02-06-2007, 08:05 AM   #4
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1 you will get a CEL
2 the idea you "need" back pressure is stupid and a myth. It's like saying you will be able to get more power running if you cover stuff your mouth 25% full of candy so you can get a little back pressure exhaling.
3 you will fail emissions
4 your car will stink like ***

but if any of that is "your bag" go nuts. A burned out cat is a warrenty issue - i.e. it gets fixed for free. If you want to run with no cat, dont be a lazy *** spend 200 bucks or so and get a race pipe or make one yourself.
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Old 02-06-2007, 09:43 AM   #5
Totally confuzzled...
 
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Throw up some sound clips if you can. I've heard what a gutted aftermarket midpipe sounds like, but never a gutted stock pipe (with resonator).
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Old 02-06-2007, 11:06 AM   #6
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[QUOTE=toxin440]1 you will get a CEL
2 the idea you "need" back pressure is stupid and a myth. It's like saying you will be able to get more power running if you cover stuff your mouth 25% full of candy so you can get a little back pressure exhaling.
3 you will fail emissions
4 your car will stink like ***

sounds good to me!
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Old 02-06-2007, 11:18 AM   #7
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The back pressure thing is not so much a myth as much as a misunderstanding.

The optimal exhaust design minimizes back pressure while maintaining an adequate air velocity to maximize the benefits of exhaust scavenging.

It's the same effect that occurs when an oversized exhaust system is used (such as a full 3" system). The top end gets more peak power because the back pressure is reduced - but - the low and mid power ranges drop.

The science behind it is the same volume of moving air (measured in cubic feet per minute) through a larger volume of space (3" pipe as opposed to a 2" pipe for example) means the exhaust's velocity is reduced.

Long story short.. reduction in exhaust velocity = reduction in effective exhaust scavenging = residual exhaust gasses in chamber = loss of power.

At least that's the way it was explained to me.
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Old 02-06-2007, 11:23 AM   #8
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All in all - it's really just best to get a hi-flow cat. Because..

1 - with the permanent check engine light, you'll never know if the light comes on for a real legitimate reason.

3 - failing emissions test means no sticker for your car (maybe not in all states). No sticker means no drive!

4 - I had a midpipe for a while.. it was bad! The fumes come back into the car even when driving - I don't know how but it does and they are rough!
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Old 02-06-2007, 11:42 AM   #9
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Exclamation Crow-bar.....

"The crowbar is my friend....."

Wear a good dust mask, the ceramic is coated with a heavy metals mixture - you don't want to find out in twenty years that the tumors in your lungs were from that cat you bashed in your garage.


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Old 02-06-2007, 12:01 PM   #10
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Cool Killed a cat....

I solved this problem for myself two years ago.

While getting my car fitted for a wide-band O2 sensor, I noticed that the secondary sensor sits in a space between blocks of catalyst. A little probing with a dental mirror showed that the cat is made of a front "bed" about three inches deep, then the space, then a rear bed about nine inches deep.

The principle is that the cat works from front to back, as the coating wears out, the reaction takes place deeper inside, until the sensor sees no difference in the gas between the first and second readings, at which time it lights the CEL for "failed cat". The only reason to have the second bed is so the car will still be OK to drive, even if you ignore the light for years. When only the first quarter of the cat is used up, the sensor will be on.

So my answer was to remove the second catalyst bed, cutting 3/4 of the material out, while maintaining full functionality, 100% legality, pass any emissions check - including a visual. Even a dealer/mechanic could not detect any problem, unless he had x-ray eyes!

Car sounds better, runs better, throws 'large' flames when prompted, and has been working like that since October 2004.

The actual removal was not as easy as it sounds - the best way would be to attack the material from its outlet instead of inlet, but that is thru the resonator and around two good bends. That way proved impossible. I succeeded by chipping away thru the sensor hole. That is also much harder than it sounds, took three days - the hole is the same size as a sparkplug hole!

If I were to do it again, I would cut the assembly in two at the back of the cat body, allowing easy removal, then get my friendly stainless steel welder buddy to put it back together.

S
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Old 02-06-2007, 05:50 PM   #11
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damn, i would have loved to see pictures...

next person to do this DIY, take pictures and post them!
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Old 02-06-2007, 05:59 PM   #12
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I always thought it had two beds for the two ways it "cleans" up the air. One for HC and CO which uses platinum and palladium and the other side Rhodium for NOx emissions. Btw instead of gutting the cat sell it when you put something else in its place. Platinum is after all a very expensive metal so cats (even burned out clogged ones) will sell for something.
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Old 02-06-2007, 06:11 PM   #13
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Quote:
Originally Posted by toxin440
1 you will get a CEL
Or not. There are a bunch of us that run with no CAT at all and NEVER get a CEL.
I've been CAT-less for nearly 3 years.

Quote:
Originally Posted by toxin440
2 the idea you "need" back pressure is stupid and a myth. It's like saying you will be able to get more power running if you cover stuff your mouth 25% full of candy so you can get a little back pressure exhaling.
True. That is explained very well by the Mighty Red elsewhere in the thread.

Quote:
Originally Posted by toxin440
3 you will fail emissions
Or not. I've passed emissions testing in Maryland both times with no CAT at all. No CEL, no fail.

Quote:
Originally Posted by toxin440
4 your car will stink like ***
Perhaps, but it doesn't smell all that great to begin with.
With proper tuning, you can run pretty lean at idle and have no additional smell.
Mine does NOT make my eyes water with the EMU the way it did with the Int-X, which ran a much more rich A/F at idle.


Quote:
Originally Posted by toxin440
A burned out cat is a warrenty issue - i.e. it gets fixed for free.
True. The emissions warranty superceeds the basic warranty by a LONG margin.

Most importantly, a gutted CAT will flow as poorly or worse than an intact CAT.
The shape of the chamber is horrible.
A midpipe is a WAY better option.
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Old 02-06-2007, 09:21 PM   #14
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Good, bad... I don't care.
I needed to get the car running. I put the DIY so others know how to do it, if they need to.
My car is FI, and runs with Interceptor-X, so I get a cell all the time anyhow.
How many FI cars run with cats? and if they do how long the cat is going to last? Not very long. Mine burned after 3K with the turbo and rather than dropping 300 on a new cat, this was a way simpler solution.
Since My turbo is remote, I do get a bit faster spool. Not much when in lower gears, but a very noticeable difference in 3rd, 4th, 5, and 6th. It starts to push air into positive at around 2500 rpms now and 5psi comes at 3000 rpm versus 3500 before. Though this can be attributed simply to the fact that the old cat did not flow well, as it was already partially busted, but who cares? Faster spool is faster spool.
Is it something you guys need or not? Go figure for yourselves, but if you do it is fairly easy to accomplish.
Someone said that it is not as easy as it sounds^^
With a hammer and a steel rod took about 5 minutes and the insides of the cat were in a garbage bag.
And Sorry I didn't take any pictures.
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Old 02-09-2007, 03:14 PM   #15
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stealth that was a good idea--what did you use to break up the material in the last part of the cat--flex rotary drill or something?
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Old 02-11-2007, 09:06 AM   #16
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Well with the help of Lowes and various plumbing tools I was able to break up that part of the cat in about 1 hr. Great DIY man. I will get it back on the car today. It will almost -imho be like a high flow cat.. I think I may post this OK Stealth?
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Old 02-11-2007, 09:12 AM   #17
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One question, the gutted out cat sound as high as a simple midpipe, lower as a resonated midpipe or somewhere in the middle?
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Old 03-04-2007, 09:43 PM   #18
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Pics/sounds/results from someone who's done this please!
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Old 06-03-2008, 01:08 PM   #19
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quick question I attempted to swap my pipe for the BB over the weekend. One of the rear studs didnt come out then attempted to remove the front bolts them selves as well but they wouldnt budge. My question is basically do any of the 2 rear studs or the front bolts have to come out to get the oem pipe out? Or is it just a matter of wedging a large screw driver in the front to seperate the flanges and simply pull it out?

Any tips are extrememly appreciated.

BTW nice DIY...
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Old 06-03-2008, 01:36 PM   #20
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Quote:
Originally Posted by zenmoused View Post
Pics/sounds/results from someone who's done this please!
yeah i did it..... with the MS cat back.

did not get any louder, just a slight change in pitch..

doesnt stink to bad as i idle a little leaner with the AP and MM's maps

i dont intend to stay this way and dont reccomend it really as it cant be good to have a huge bulge in the exhaust stream.... i did it for a quick temporary fix to a dilema i faced
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Old 10-19-2009, 10:18 PM   #21
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If you suddenly experience a loss of power at around 4K rpm and your car just refused to go, there is a very good chance the your CAT is gone.
I had just spent a week trying to figure out what was wrong with my car, just to find that the reason for it all was a burned cat.

This DIY is for those of you, who always thought of getting a catless midpipe, but never got their hands to do it and waited long enough until their cat has finally failed, or whatever the reason it might be that you want to run your car catalytic converter.

Here is a clean and simple way of doing it, without spending any money.

1. Take off your cat.
Taking it off is very straightforward.
All you neet is to disconnect the oxygen sensor from the connector jst above it.
Unscrew three 14mm nuts on the front joint, two 14mm nuts on the back joint, detach the 2 horizontal support panels by unbolting 12 mm bolts that hold them in place (4 in each) and finally pulling off the rubber mount.
Even after you take off everything that holds your cat, the pipe will remain in place. To get it off grab a large screwdriver (carefully not to damage the metal ring in there) jam it between the flanges on the front join and using the screwdriver as a lever separate the joint. Once it is out, Just pull the whole pipe out of the rear joint.

2. Take out the Oxygen sensor:
Remove the sensor guard by unscrewing two 10mm nuts.
Unscrew and remove the sensor.

2. Gutting your cat.
Get a 11/2-2 foot long half 1/2" steel rod or something similar ( Home depot for about a buck ) and a hammer.
Flip the pipe vertically with the front (triangular flange facing up)
stick the rod inside the cat opening and using the hammer keep on whacking the internals until the rod breaks through. The is made of 2 parts, meaning that there are actually 2 elements inside that pipe, so when you break the first one, shake the pieces out, and continue whacking on it and shaking stuff out until there is nothing left. Use a light to see inside to make sure that it is empty. When everything is out, you'll see that the inside walls of that (now just resonator) are relatively clear and there is nothing left.

This is it. Now you are a proud owner of a completely stock looking catless midpipe
Reinstall the sensor, and put everything back following the directions above in reverse.
Happy modding.

P.S
The dual structure of the cat is actually the reason the car looses power when the damn thing burns out. When the cat goes, the debris from the front part of the converter (which takes most of the abuse) completely clogs up the second portion of it, and blocks that exhaust flow.
Your engine simply can't breathe and so it starts to loose power more and more, and if you continue on pushing it, the cat will eventually clog completely, causing the engine to just shut off.
Thanks for the tip I might use it these coming weekend. I ordered some sets of them & will replace older set.
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Old 02-26-2010, 05:49 PM   #22
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Finally gutted mine

Clogged cat so i finally gutted it. And here is a video of what this sounds like. Ill throw up some photos of the actually gutting it just to give an idea. Took about a hour or so to do. Quick once i remembered you need a hammer to do it lol...Also... very happy with results... just wish it was a tad bit louder![EMBED]<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/WVjP174cgCI&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/WVjP174cgCI&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>[/EMBED]
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Old 03-17-2010, 09:50 PM   #23
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Please read !!!!

giving away your Catalytic Converter ?
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Old 03-24-2010, 12:54 PM   #24
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SO... ummmmm ya i do got bored when swapping my clutch since the midpipe was already off i gutted it for the hell of it and that + my custom catback = I Breath Fire gotta love our rotarys they run so rich no CEL either and no bad smell on my end but it did improve my gas milage it seems aswell as i have a little faster of a take off maybe not sure have to do a run this weekend to find out if you have a CEL for ur sensor advanced auto and autozone sell plugs for the sensor spark plug defouler plug and that will make the sensor useless and remove the light
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Old 03-24-2010, 06:31 PM   #25
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For whatever reason i fail to shoot flames. ) =
Gutted cat, but i must be doing it wrong lol...
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Old 03-24-2010, 06:31 PM
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