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-   -   how to make oem cat into a high flow one (https://www.rx8club.com/series-i-tech-garage-22/how-make-oem-cat-into-high-flow-one-109362/)

zenmoused 08-30-2007 10:28 PM


Originally Posted by dothackRAVE (Post 2036093)
Ya know..., you guys can chalk up $500 for a MazdaSpeed exhaust. I have one, and god damned, it makes Rena purr. I've seen many RX8s around town, but none sound as good as Rena. It has an authentic rumble to it, unlike cheap "custom jobs" that any fool can tell from afar that you did it in your garage.

Are you talking about the CAT-BACK mazdaspeed exhaust? Because that actually has nothing to do with what people in this thread are doing. They're talking about (partially) gutting the cat, which is before the part the mazdaspeed replaces.

dothackRAVE 08-31-2007 07:05 AM


Originally Posted by zenmoused (Post 2036102)
Are you talking about the CAT-BACK mazdaspeed exhaust? Because that actually has nothing to do with what people in this thread are doing. They're talking about (partially) gutting the cat, which is before the part the mazdaspeed replaces.

Oh. I thought they were talking about taking out the "bulged parts" and gutting them.

CnnmnSchnpps 08-31-2007 07:14 AM


Originally Posted by dothackRAVE (Post 2036284)
Oh. I thought they were talking about taking out the "bulged parts" and gutting them.

:lol2:

Don't you be touching my bulged parts...

Seriously though, this thread is about gutting the catalytic converter, which is under the car (yes, a bulged part... close to your transmission and what provides the cup warming effect)... It also happens to be the single most restrictive piece of the exhaust system, hence removing / gutting.

By the way, I seem to remember that the two parts of the cat actually clean the exhaust of two different gases, but for the life of me I can't remember where I read that.

dothackRAVE 08-31-2007 07:29 AM

Well, thinking about it:

7" of consumable catalyst, and 3" of safety catalyst.

I'm guessing you're gutting it for a little extra horsepower (if not for acoustic purposes). So you mean..., the longer I drive this thing, the more power I get...? That honestly sounds farfetched.

Why is why I thought you guys should just get a MazdaSpeed exhaust.

mac11 08-31-2007 07:31 AM

what the hell do you mean the longer you drive this thing the more power you will get? where did that come from?

And I am going to assume this is your first rotary vehicle? They run quite a bit louder than piston motors naturally so you can really tell Mazda used a very baffled muffler and cat from the factory to get the car as quiet as it is. With as much as the cat itself quiets down the car there is a good amount of restriction in that piece. You will see the biggest improvement in power by replacing the cat as compared to a cat back exhaust, header, intake, u/d pullies, etc.

zenmoused 08-31-2007 09:06 AM

anyway- I'm probably going to tackle this project tomorrow and see what kind of gains I can get. I figure if I REALLY screw something up, I can always buy a supercat like I was originally planning. I'll take pictures for everyone's enjoyment... maybe do a little DIY :-)

TaterTot_USMC 08-31-2007 10:24 AM

So, this is my first Rotary engine. I have been perusing the posts for about 2 months now to find out what kinds of mods i can do to get more audio/visual flare out of my car for little money (gotta love military salary). This seems like a good candidate as it sound fairly cheap and effective.

Question though: the flames, when do you start to see flames coming out...and is that only with an aftermarket muffler, i am thinking about making a custom exhaust come out the center, would this cat mod make a single exhaust too hot?

zenmoused 08-31-2007 11:24 AM

Nope, I've gotten flames with a completely stock exhaust. The most effective way of producing them though is getting a hi-flow cat or midpipe. The stock muffler isn't too restrictive.

Silver_Surfer 08-31-2007 11:25 AM

Will give it a try this long weekend. PRAYING everything goes OK!!!!!!!!!!!!

Wifes already seen me putting car on jackstands. "Now what-ya doing to your car??:banghead:


:lol2: :lol2: :lol2:

zenmoused 08-31-2007 02:45 PM

Silver- I'm doing mine tomorrow... if you get to yours beforehand, or if you're near your computer, please post your progress and any tips you may have!

DOMINION 09-01-2007 01:20 PM


Originally Posted by olddragger (Post 1733668)
:bowdown: Thanks to Stealth for this finding!!! You rock dude :bowdown:

All that are interested please see the gutting your cat thread in this section. Stealth told us his finding and I am passing it on. The thread has this info and I will tell you how I got it done in a shorter period of time.
That 9" of "extra cat material" can be removed from the rear by just obtaining a 5ft section of 1/4 inch threaded rod from Home Depo/Lowes and ramming it repeatively into it. This size rod is thin enough to go around the bends of the assembly but strong enough to break up the ceramic.. Be sure to mark the rod to the dept you need(you dont want to go into the front section of the cat) and dont go past it. The rod can be bent on the end to increase the area it cleans as you go. Wear a mask when you are doing this as when you are shaking out the pipe to clear it --it can get a little dusty and I wouldnt think you want to beathe that stuff into your lungs.
Damn good find.
olddragger :rofl:

Right, I'm new to all this cat stuff. Can someone point out to me what we're doing?
From what I get you take a 5ft 1/4 inch threaded rod mark it, then hammer it into the _______ on the cat?

How deep do you need to go when your braking up the ceramic? 9"?

Shaking out the pipe to clear it. What pip? the one I'm useing to brak up the ceramic?

About how much time will this take?

Thank you

mac11 09-01-2007 01:40 PM


Originally Posted by DOMINION (Post 2037869)
Right, I'm new to all this cat stuff. Can someone point out to me what we're doing?
From what I get you take a 5ft 1/4 inch threaded rod mark it, then hammer it into the _______ on the cat?

How deep do you need to go when your braking up the ceramic? 9"?

no further than the end of the rear brick of ceramic. or no further than the opening for the 02 sensor.

Shaking out the pipe to clear it. What pipe? the one I'm useing to brak up the ceramic?

the piece of pipe the catalytic is welded too. If you unbolt the section of pipe the cat is on and look at it the directions will make complete sense.

About how much time will this take?

hour. maybe 2. did this on an old car.


Thank you

you're welcome.

DOMINION 09-01-2007 01:47 PM

I'm getting sick of you real quick.













Thats just too quick lol thanks!

mac11 09-01-2007 01:56 PM

what?

DOMINION 09-01-2007 02:20 PM

That was sarcasm ;)

Can you point out the part that we are hammer into? please.
1. Front of car is to the left
http://img508.imageshack.us/img508/867/p9010930fr8.jpg
2. Mid
http://img508.imageshack.us/img508/5617/p9010931kd3.jpg
3. Rear
http://img410.imageshack.us/img410/1880/p9010932mr3.jpg
Thanks

StealthTL 09-01-2007 02:32 PM

First you have to take it out, and stand it upright, "front" part up.

The first pic shows the O2 sensor , this is the hole I used. Rods curved towards the back, smashed the ceramic substrate, the pieces fall out thru the resonator (pics 2 and 3)

Olddragger went in thru the resonator, with a carefully measured rods.

The piece of catalyst that must remain is in "front" of the O2 sensor space.

S

HCTR154 09-01-2007 02:36 PM


Originally Posted by Silver_Surfer (Post 2036619)
Will give it a try this long weekend. PRAYING everything goes OK!!!!!!!!!!!!

Wifes already seen me putting car on jackstands. "Now what-ya doing to your car??:banghead:


:lol2: :lol2: :lol2:


^^^^I thought I was the only one to hear that!! :rolleyes:

DOMINION 09-01-2007 02:47 PM


Originally Posted by StealthTL (Post 2037953)
First you have to take it out, and stand it upright, "front" part up.

The first pic shows the O2 sensor , this is the hole I used. Rods curved towards the back, smashed the ceramic substrate, the pieces fall out thru the resonator (pics 2 and 3)

Olddragger went in thru the resonator, with a carefully measured rods.

The piece of catalyst that must remain is in "front" of the O2 sensor space.

S

OK cool. So I should not start from this point right?
http://img407.imageshack.us/img407/6...large29tf2.jpg
and crap like this should fall out right?
http://img236.imageshack.us/img236/4...2818429ij5.jpg
Thanks

StealthTL 09-01-2007 02:51 PM

Absolutely not!

....of course, that would be WAY too easy!

Your cat should still look pristine like that when the job is finished, or you get a big fat FAIL!

Yes, the pieces will look like that. If you work thru the resonator, be SURE that stuff doesn't get rammed into that first bed.

S

DOMINION 09-01-2007 03:06 PM


Originally Posted by StealthTL (Post 2037969)
Absolutely not!

....of course, that would be WAY too easy!

Your cat should still look pristine like that when the job is finished, or you get a big fat FAIL!

Yes, the pieces will look like that. If you work thru the resonator, be SURE that stuff doesn't get rammed into that first bed.

S

Right but I'm not and you said to take it off so my next question is; Can I use something to drill it out vs ramming it? wont that compromise the front ceramic structure?
Thanks

StealthTL 09-01-2007 03:10 PM

I'm not proud of the technique I used, almost ANY other method would be easier/work better/faster.

You aren't trying to do it all from that position, are you?

S

DOMINION 09-01-2007 03:16 PM

No I hear you but, what I'm asking is;
If I take my cat off and do what you said;"First you have to take it out, and stand it upright, "front" part up." then I should be ok drilling out from the back of the cat starting with the part that is facing the back of the car right?

That make sense?

I mean can just drill the end out useing a drill bit on my black and decker and start drilling from the back of the cat up to the front where the O2 sensor is right? but dont pass the O2 sensor right?

**Thanks STL thats what I was looking for**

Silver_Surfer 09-01-2007 03:45 PM

Started mine. Tight exhaust bolts is an understatement! After checking it out, DAM the 02 sensor hole is small! After about an hour of crunching from the 02 hole. Still unable to reach the rear portion of cat material, I did'nt have a long bar handy. Found my dewy gun cleanning rod would work. Will start later this afternoon when its cooler and start working it from both ends.

***For you people who already done this mod. Theres no way all the rear 9" portion of the cat can be cleanned up entirely(Clean). You're just doing this mod to increase flow. Right? Or is there more to this mod?***

Silver_Surfer 09-01-2007 03:48 PM


Originally Posted by DOMINION (Post 2037992)
No I hear you but, what I'm asking is;
If I take my cat off and do what you said;"First you have to take it out, and stand it upright, "front" part up." then I should be ok drilling out from the back of the cat starting with the part that is facing the back of the car right?

That make sense?

I mean can just drill the end out useing a drill bit on my black and decker and start drilling from the back of the cat up to the front where the O2 sensor is right? but dont pass the O2 sensor right?

**Thanks STL thats what I was looking for**


No, its not that easy! Craw under your car and check it out. From the rear end the rod has to snake through the resanator to reach the rear portion of the cat.

***THIS IS NOT AN EASY JOB!!!***

DOMINION 09-01-2007 03:56 PM

Thanks but STL beat you to it ;)
See pic
http://img409.imageshack.us/img409/5...io20catef1.jpg


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