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.

you right about it,i've done it last year :) but lack of words to wrote it :D: anyway good write up for DIY :icon_tup:

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?

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 ass

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 ass spend 200 bucks or so and get a race pipe or make one yourself.

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).

[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 ass

sounds good to me!

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.

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!

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.


S

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

damn, i would have loved to see pictures...

next person to do this DIY, take pictures and post them!

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.

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.

True. That is explained very well by the Mighty Red elsewhere in the thread.

Or not. I've passed emissions testing in Maryland both times with no CAT at all. No CEL, no fail.

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.


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.

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.
:ylsuper:

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?
olddragger

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?
olddragger

One question, the gutted out cat sound as high as a simple midpipe, lower as a resonated midpipe or somewhere in the middle?

Pics/sounds/results from someone who's done this please!

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...

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

Thanks for the tip I might use it these coming weekend. I ordered some sets of them & will replace older set.

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]

Please read !!!!

https://www.rx8club.com/rx-8-parts-sale-wanted-44/giving-away-your-catalytic-converter-193352/

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

For whatever reason i fail to shoot flames. ) =
Gutted cat, but i must be doing it wrong lol...

what catback do you use mine i used factory mazda and just removed the muffler and Y piped it aswell as i run a mixture of 91 and 100 octane gotta love race fuel

okay so i gutted my cat(all of it) throttle response is better & i can feel the engine picks up quicker, but now im getting a cel light. so im doing the non fouler mod & i will post on how that works.

1 week and no cel light. non-fouler is working good.

I run 93 in my eight. And yeah, no flames but either way haha... and yeah, the whole non-fouler thing has been tried a whole bunch without any long term success from what i understand. Lemme know if it works though, might be worth pickin up.

Pics tomorrow, maybe a vid too, i get such great POPs now 3rd gear just tapping the gas and a nice flash at night, i just gutted mine yesterday and installed it, had to buy new bolts and washers and nuts because i stripped RPs threaded pipe , suced ass was too late with my air tools turned up. but over all smells better and sounds cleaner. i like that boat smell :) but the stock cat gets way better mpg. over all rp or any high flow replacement pipe is worth is accel is better and revs are, but keep that old cat for smog reasons imo. good tread thanks again.

There is a demand for cat's out there. Trade your working cat for a straight midpipe.

Just gutted converter
 

Thanks to all the comments posted on here i wasn't to sure weather or not i wanted to gut my converter but i know it was getting red hot from driving a long distance then quickly checking under the car to see if it was red and yep just like santa's coat. I didn't have the money to get an mid pipe due to i just got the car completly tuned up and was short on cash so i took a chance and yeah there is an lil bump in power but i lost on top end but i don't go that high anyway and my engine light just came on :scared: after 3hrs of driving which i already know what its going to say :tear:

Ok so a couple questions-

- would doing this decrease the mpg?

-does it increase the hp at all?

- should I do this if the cat is just starting to go bad, but still livable (it is setting off the sensors though) or would it be better for the car to just keep the cat?

-how much louder does it make the car?

Just did this mod to my 8, in addition to doing the seafoam treatment, and WOW, that made a world of difference!!!!! I had 4 CEL codes on before I did this and now they are all gone. Idk whether it was all the seafoam, or all the pipe but it worked wonders. Highly recomended.

You left out the first step; gutting out your common sense. :bash:

well like i said when i gutted my cat it gave me a little bump but it sounds awesome i made a youtube clip so you guys can hear it. It really did increase gas mpg when regular driving but it decrease when at full throttle. but what hp gain don't.
http://www.google.com/url?sa=t&sourc...wbPrHJ7rgCdE_g

Pshhh whats that supposed to mean??? F^%@ u too

so is there a glowing red light around the o2 sensor on the cat is it the cat thats clogged up or is it the o2 sensor that needs replacing????

The red you see is just the hole for the sensor, there's no shielding there, so it's visible.

It doesn't mean the cat nor the sensor is bad, it's pretty much normal.


S

but you see u havent seen the thread i posted my 8 is messing up is shaking severely and well u c the vid

https://www.rx8club.com/series-i-trouble-shooting-95/help-me-identify-problem-please-video-206100/

No I haven't - that's why it is a good idea not to start THREE threads about the same problem.

.....but keep asking until you get the answer you want, by all means.


S

No I haven't - that's why it is a good idea not to start THREE threads about the same problem.

.....but keep asking until you get the answer you want, by all means.


S

errr my car light went off and came back on when the weather changed from hot as hell to cold as fuck but i heard there is something you can buy called an by pass valve or something i'm going to research it and see if it works unless somebody already did

[/quote]It helps me out of the problem, Thanks for your analysis! Nice writing.
 

[quote=toxin440;1725990]1 you will get a CEL2 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 emissions4 your car will stink like assbut 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 ass spend 200 bucks or so and get a race pipe or make one yourself.

yeah i was going to get a mid pipe but i needed get this cat from turning hot right now. i already ordered my hks lega exhaust and and a mid pipe i'm just waiting for it to come in and where i live there is no passing emissions because we don't have it num nuts

dont know if im the only one, but does anyone else have the thread stripping nuts on the header bolts? i started taking the pipe out, got everything done except the header bolt/nuts. i cant get the bottom one halfway off w/ breaker bar and impact wrench. i tightened it back b/c it was getting late last night and noticed the nut stripped the threads clean. not just stripped the threads a bit; no there were no threads left(except at the end where i had given up). wondering if anybody is having this issue or not, im gonna take it up to a muffler shop and have them take the bastard off

Ya those damn bolts. I only stripped one; but, it seems like the ones mazda used are knocked in and use like a counter thread so they don't move easily. I just took off my oem cat pipe cause it was shot and put on that rx7store high flow cat pipe to pass smog. Plan on gutting the old pipe this week and putting it back on and just keeping the new one around. I don't know. Well anyways, ya i pulled up to my buddies shop and we just cut those suckers off. Made one long day but the cars sounds good. Will sound better I think with the old pipe gutted. Probably won't even buy a new cat back. the stock one sounds fine with the messing around with different mid pipes.

Also, anyone with a gutting oem mid pipe... Did you fill the o2 sensor spot with a anything? or left it open? To me i would think to fill it; but, any input is good.

Thanks

What code would the cel would pull up if it was a bad cat.
Thank you guys

Ok... my cat is off... I'm goin at it with a small metal rod and screwdriver through the O2 sensor hole... Tryin to pull it off like Stealth did... Has anyone else tried this? If so, what the hell did you use to gut this bad boy?

I used a 3 foot metal rod and knocked it out through the front opening. Don't go through the O2 sensor hole. You might damage it.