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Discussion Starter #1
Hey guys I searched, searched, and searched for two days now about this cat failure and got a little information but not the whole answer im looking for. Ok so I found out we have 4 cats...two pre cats on the headers and two actuall cats under the car...I want to avoid f***ing up my engine so I want your guys advice. Can someone take pics and point to the cats? I want to know exactly where they at...Also does replacing my headers with MSDS and putting straight pipes instead of the cats under the car fix all of my problems that i may encounter? I have almost 118k on my car thats why its worrying me so please anyone know any lil bit of info post your responses as it will be much appreciated. Thanks in advance.
 

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There is nothing to point at. You either leave them or replace them. A misfire (bad plugs or coil etc) will cause premature wear on the pre cats and will kill your engine. Proper maintenance will help eliminate that problem. Only way to completely avoid this is get the MSDS or NPG headers and add a high flow cat.
 

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Discussion Starter #3
ok well thats what I want to do...MSDS headers and a high flow cat...any recommended websites you know of that have good service?
 

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I just punched out my precats. Didn't cost anything and no worries about passing the visual emission inspection.
 

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what do you mean by "punched out"? banged the living shit out of them till everything came loose and cleaned it out? lol
 

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for all the work it takes to get the sob's off... ^ sounds like a bad idea, you miss any and you will suck em up the egr and defeat the purpose. if you have the time and ability to take them off then putting MSDS on would be easy.
 

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Discussion Starter #11
well then im not doing that and taking a chance...ill just buy the MSDS headers from their website and like a Magnaflow High Flow cat from their website also and post pics and a video later...total its going to be close to $1100
 

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what do you mean by "punched out"? banged the living shit out of them till everything came loose and cleaned it out? lol
What state are you in? Do you have to worry about inspections? I have a complete set of cats off an 03 that have been completly cleaned out. I used them until I put on my MSDS headers. Willing to part with them for cheap, but they weigh like 56 pounds so $$$ to ship UPS. Below is some info on gutting cats and some pictures.

Gutting the rear precat is easy because you have a straight shot up into it from the outlet end. The front one is really hard because you have to do it all through the O2 sensor hole. Unfortunately my car did both of them all by itself. All that was left inside the precats was the mesh separator rings laying in the bottom. The rest of the stuff flushed down stream and clogged the secondaries. Check out the pile of stuff I poured out of secondaries and tailpipe. When the ceramic does break-up it sparates cleanly from the interior with no residue like a metalic CAT.

The second picture is a side by side of the stock 03 exhaust and an MSDS header CAT-less set-up. A hi-flow CAT can be installed in the straight section of pipe at the far right if you wish.

For those confused about how many CATs there are look at the stock set-up. There are 2 preCATs (1 in each header) about the size of a coffee can. Then there are 2 secondary CATs just downstream. The front/right bank one is directly under the oil pan and the rear/left bank one is back in the y-pipe just behind the subframe and 2 braided flex tubes.
Attached Thumbnails
 

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Discussion Starter #13
oh wow see thats the answer im looking for...i can now go under my car and see that same exact pic u posted and know what im looking at...I now understand everything thanks to you...so what kind of high flow cat did you get? basically what im trying to get at is i want exactly what in the pic...MSDS headers with high flow cat...where did you buy them from? and I dont care about emissions n all the state inspection bullshit haha
 

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I got mine straight from MSDS, but if you look at the pic you'll notice something a little odd with the new pipe layout. I put a 07 engine (with the upgraded oil pan) into my 03 body and subframe. Marty at MSDS set me up with the beautiful set you see in the picture that made it all work. He now has kits for normal 03-05's, normal 06-08's and a blended set up like I did that lets you combine the 2. If you have any appreciation of metal work, the bends on my y-pipe to go up over the older subframe are spectacular.
I currently am running without a cat, so I can collect performance data for a "before and after" comparison. Later this spring I will install a Magnaflow based on exhaust pipe and engine size.
 

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Discussion Starter #15
oh i see...nah i have a stock 2004 mazda 6s v6 with 118k all original even clutch lol and thats why i wanted to do this cuz of the high miles...so im just going to buy msds off of their site and then put straight pipes all they way back...drive it for a week and see if i like it or if its too loud n then do some adjusments...first the magnaflow catback exahust system n then drive for another week to see if i like it...n if i dont i will put a magnaflow cat and then hopefully i like it...hahaha so do u think its going to loud as hell if i do MSDS and straight pipes no cat? cuz i have straight pipes now and it sounds beautiful not too loud and not too quiet...i can bare with it
 

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i still dont understand how you punched those things out without cutting them
The front precat I used a long screwdriver through the top O2 bung. The rear is easily accessed through the exhaust pipe.

what do you mean by "punched out"? banged the living shit out of them till everything came loose and cleaned it out? lol
You use a chisel to break up the ceramic catalyst then dump it out. The catalyst is not bonded to the sides at all so when its broken up it all falls right out. There is also this white fluffy stuff that I believe is some sort of insulation that will also come out.
 

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oh i see...nah i have a stock 2004 mazda 6s v6 with 118k all original even clutch lol and thats why i wanted to do this cuz of the high miles...so im just going to buy msds off of their site and then put straight pipes all they way back...drive it for a week and see if i like it or if its too loud n then do some adjusments...first the magnaflow catback exahust system n then drive for another week to see if i like it...n if i dont i will put a magnaflow cat and then hopefully i like it...hahaha so do u think its going to loud as hell if i do MSDS and straight pipes no cat? cuz i have straight pipes now and it sounds beautiful not too loud and not too quiet...i can bare with it
It will be louder, but sound is so subjective. I have the headers and stock from the cat back. I think it sounds fine, but other members think it is loud. You'll just have to see.
 

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for all the work it takes to get the sob's off... ^ sounds like a bad idea, you miss any and you will suck em up the egr and defeat the purpose. if you have the time and ability to take them off then putting MSDS on would be easy.
I made absolutely sure there was nothing left which was pretty easy since the catalyst material is not bonded to anything. Taking the exhaust apart was the most difficult part but I had to weld the front manifold so it had to come off anyway. Now I don't have clogged cats or the visual emission inspection to worry about.
 

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Discussion Starter #20
I would say the same failure cuz I heard alot about Mazda 6 in general their exhaust was so poorly designed
 
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