Hi all,

I recently purchased a 04 6 speed. Well 40 miles after purchase I now have (sel)
Mazda says I need a new cat. I want a good cat that will get rid of sel and not brake the bank.
Any suggestions, anyone run into a brand or specific cat that isn't good to buy.

 

There are really no cheap cats that are going to work well. How cheap are you wanting to go? You can buy a used cat from someone on the forums for ~300-400 I think.

 

Not cheap just not mazda prices. Not looking for any hp gains just something that will do it's job. For example at autozone there are either a walker direct fit for $233 or magna flow universal for like a$100 will any of these work or just garbage that will fail next year




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Most replacements should offer a warranty, just save your reciept. I'm running a high flow magnaflow that i custom made. Works great!

 

Dont have cat tore out yet so can anyone enlighten me as to pipe dia and length needed for universal type so I can get it ordered

 

You will for sure melt/destroy a universal cat. A bad cat can take your engine out as well, so either spend the money now(even the used mazda one I mentioned above) or end up possibly spending more later. The davesport cat that BHR puts in their midpipes seems to work good, maybe talk to them and see which model it is.

My car with a midpipe puts out around 1600 degree temps, not sure where that gets measured but you will only increase heat with a restriction in there(the cat) so expect hotter than that. So make sure you find out if the cat you will be getting can handle that, the davesport does fine I think.

If your cat died, make sure your ignition is healthy. Since you just purchased the car you should consider replacing the coils, plugs, and maybe even the wires. Unless you have all the maintenance history and know they were replaced somewhat recently.

 

Oh cool, then my $100 Magnaflow metallic-substrate cat #59959 really isn't working after 11,000 hard miles? And the Davesport on the BHR midpipe isn't being reported as failing after as little as one track day or a few WOT runs?

Unless you have an extra EGT specific sensor installed, you don't know what the temps really are.

The only correct advice you gave is to figure out why the cat failed and fix that problem. Otherwise a replacement will fail too.

I suggest the OP search and read the various threads on this exact same topic.

 

Depends how you want to do it. Work it out yourself with the guy who's gonna do the welding.

 

People have melted lots of metallic cats in the past. Yours may last and be a good solution for whatever amount of miles and at $100 isn't bad to replace but I have no clue about it. Don't act like people should have somehow read every single post on this forum to do with a cat, and if they didn't they are somehow wrong about everything. Not meaning that in a rude way, just be a little more couth is the nicest way I can think to say it.

For the most part the people I have seen that had the davesport cat fail were either boosted or using nitrous. There was another guy who had it fail in 1 autox run I think.

I'm just going by what the ecu states the cat temp is.

 

Your post reads as written from a viewpoint of absolute authority. "You will for sure destroy/melt a universal cat" is a statement that is both authoritative and simply not true. For example, HKS makes a universal cat that is generally regarded as being robust for n/a use, though it does cost a lot.

This is fair: "I'm just going by what the ecu states the cat temp is." You are reporting a reading you saw and where it came from.

This is also fair: "There was another guy who had it fail in 1 autox run I think." That is you think you remember reading about this happening. A reader can then make up his own mind or do further investigation, perhaps concluding that a cat which can die in 60 seconds of hard running isn't so great.

See the difference?

 

Have you actually had it eTested?

I've been looking for another solution, and every CAT I've tested fails the sniff test.
(not including the OEM cat)

 

Good point. I've not had a sniffer test done on the $100 Magnaflow; I only note that it runs without smell or CEL.

 

I had it in the mazda garage that I heard was a good place to take it. All I was told was it looked like a mouse had chewed on down stream o2 sensor wires, so that needed changed and primary cat is98% plugged and that needed changed or may damage engine. So I have dementions now if I do go with universal do I go with metallic or ceramic

 

Also looks like plug wires are new and coils look old. Not sure about plugs yet.

 

Oh ya and car does have 80k on it.

 

in California we have one choice, the stock OEM cat. current list is $1385.

outside of CA there is a Magnaflow for like $600. there is also a walker direct bolt in for $300. 2005 Mazda RX-8 Catalytic Converter - Buy 2005 Mazda RX-8 Catalytic Converter Online

i don't know about the performance aftermarket.

you can assume the OEM converter will outlast anything else by a factor of at least two

 

Ordered magnaflow cat. 99356hm. Direct fit just not bolt on must be welded. Also ordered new o2 sensor and cat back system. Cant wait for all to come in and get back on the road.


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I wouldn't trust Walker at all, last time I bought 2 Walker direct fit exhaust (muffler) for my FC/S5. that **** was WAY off, it knocks on the body of the car. I got mad pissed and returned it the 2nd day, ordered 2 brand new OEM. perfect.

 

I think it is pretty fair to say that he would destroy a universal cat. He was asking about a low cost solution from autozone. I did some digging and all I can find is a post by you about the cat you bought so others have not tried it or didn't feel the need to talk about it. If you do a search for replacement cats you find pretty much the same info "oem or you will kill it fast" with a sprinkling of teamrx8 talking about the HJS cat. You would have more cat knowledge than I do since you actually have one and probably spent the time researching, I just went off the general consensus of the forum in other threads.

I think you mean HJS and not HKS? I didn't tell him to try that one because he seemed to want to pay less than a used oem on the forums, which he later confirmed. The HJS one is $500+ Isn't it? I believe it is also a high flow cat and may not pass the sniffer test in whatever places still have it.


Censming if you have no papers showing when the coils/plugs/wires were replaced and you already stated at least the coils looked old you might as well replace them. There are some very low cost coils from autozone or you can get the higher priced oem ones. The plugs are pretty much $80 for the set of 4 anywhere you go without a coupon(make sure you get 2 trailing and 2 leading), you can get a cheap set of ngk wires from rockauto.

 

Still not race / forced induction friendly? Curious if you were able to improve upon it. My wife would be very happy with me if I put a cat back on my 8.

 

Update: All of my parts are in. Removed old exhaust system and there wasn't any material in the cat at all. Previous owner gutted it. I contacted the BBB about the dealership telling me that it was 98% plugged. Ohmed o2 sensor and it was good 2. I love dealerships you can't trust. I'm going to put all new on bc I got dealership I got car from to give me a check for the parts.


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Everything is in and sounds great nice tone. Got a 4caroption cat back system for under $200. Quality seems really good. Time will tell how good it really is. Now the wait to see if sel comes back.

 

You'll want to solve the problem that killed your cat in the first place, which is likely the ignition coils. If you don't know when those were last changed, change them.

 

Ya I figured they probably needed changed. Coils, wires and plugs will get here tomorrow. Cat was hollowed out so who knows when the previous owner had problems with it. Guess beter to start with a clean slate.

 

I hope you can weld. If not, you will be able to after the third cat goes in. Also, good luck with that ebay exhaust. I just removed one for a friend after being on for a year. Looked like a supreme rusted pile of crap. The tips still looked really cool, though. So I guess that's good to look forward to.