Aftermarket Catalytic Converter

[TheNextEpisode]

Ever since my H swap, I've been running aftermarket cats. They seem to be effective during the first 6 months, and after that, judging by the smell of my exhaust and the terrible smog test numbers I get 18 months later, they completely stop working. I'll then replace the cat with a new aftermarket cat, pass smog easily, and be good for about another 6 months.

I've used a CATCO cat and 2 Magnaflow cats. At this point, I'm assuming aftermarket cats are just crappy across the board. Is my assumption correct? Do other brands fair any better?

[King James]

Hmmm....How many miles do you drive in that 6 months....Im more concerned cuz Im about to buy a hi-flow magnaflow for my cressida....and if you drive a comparable number of miles to me I dont want it going bad in six months....probably less as Ill have 2 turbos and 2 more cylinders feeding the fucker

Ive googled it and it seems to be hit or miss....some people say they are good to go....and some say they are going bad after 6 months....this was mostly stock cars though.

I did learn thought that OEM cats are required by law to last 100k....unsure what aftermarket are supposed to last....but maybe they arent so stringent thus the problems.

[TheNextEpisode]

It varied between cats, but it was between 3 and 6 thousand miles. One of them seemed to last nearly a year, but I don't recall which.

Even when I was running the stock F22, which was last time, the cat failed real quick. I would suspect other emission issues with my car, but the car passes fine once I swap to a new cat.

When I switched to 2.5" exhaust, I didn't think to ask for my old cat back. It was doing fine at 190k when I swapped it, so I'm definitely looking to [illegally] buy another used oem one.

[Warudakumi]

From my understanding a aftermarket ceramic cat will never perform as well as a OEM period! Just like you I had to swap out cats every time I smogged my car. I finally gave up and started getting hot smogs because I couldn't justify the price of another magnaflow and the labor of having one welded on everytime to my custom exhaust.

The smell you are smelling is your car running too rich... most likely unburnt fuel being thrown at your cat(are u doing v-tAk runs often? or spirited high rpm shifting?) When your car runs like this all the time and if you drive hard as well, those highflowing ones especially don't tend to last as long no matter how much you pay..... This was my case anyways. Maybe some fine tuning or better ignition components can help you out? I've never heard of a F22 running uber rich. My first CB had a JDM auto H22 and I could wipe the exhaust clean of deposits and the next day it's almost black again :P

The best thing you can do is find yourself a SRT-4 cat and make it "hot swappable" everytime you want to smog your car.

[King James]

Thats actually what I was thinking for me....cuz I was concerned about passing smog with an aftermarket cat (I dunno how well the 1J does for smogs)....So I was thinking keep the oem as a bolt in for smogs then run test pipe for daily use.

Sorry for the kinda OT

[TheNextEpisode]

Yeah it does seem like its a rich-scent. I've been running the F22 for the last 15k miles, though, and have been had the same problems. I drive like a grandma too, so I'm not entirely sure what the deal is. Thanks for the suggestions, regardless.

What is the SRT4 Cat you're referring to? Do you mean the Neon SRT4 oem cat? That sounds awesome, assuming the price is reasonable.

ninja edit: all good on the OT, we're having the same issue.

[deevergote]

I know SMSP makes some decent looking performance cats... and SMSP is known for making great stuff (well, headers anyway), so I wouldn't expect them to sell crap. Other than that, OEM is all I'd go with.

[wed3k]

id try and find out why you are taking out cats...misfires, consumption issues, leaks, too high egt's?

[Losiracer2]

something's definitely causing the cat to burn up it sounds like.

You must be running really hot causing the honeycomb material to break down. I'd suspect something's wrong with your engine and not the cats if you've been through that many. What do the old cats look like after you get done with them?

I'm running an aftermarket high flow 2.5" cat on my H22 and it passed emissions no problem, I even passed with a Random Technology 2" high flow cat the time before that so it's more than likely your engine causing you issues.

[TheNextEpisode]

^ How recently after replacing the cat did you get that smog test?

I don't burn oil (seemingly at all), the oil pan stays clean and dry, and I get no misfires, no CELs, and no soot around the tailpipe. And, like I've said, when I change to a new cat, I pass well under smog requirements. I guess I could be running rich? That would be kinda cool, since I've already been getting 40-45 mpg for the last couple thousand miles.

I guess EGTs could be an issue then, I've been using a wrapped DC header which might be contributing to heat being transferred to the cat.

[YK86]

I've been using aftermarket Walker brand cats (oem direct fit) and so far, it's been fine for all the cars I get them for. This includes my 4th gen Accord that I have driven for over 6 years and 50,0000miles with the "new" cat and pass emissions with flying colors every year.

But it is quite certain the oems are expensive (and last longer) due to the greater amounts of precious metals they use vs the cheaper aftermarket. The only high flow cat I've had was a Bassani for my Mustang but those were crap and didn't pass emissions even when brand new but that's a totally different car.

One thing that caught my eye was 40-45mpg??? That sounds really high. Maybe your car is running too lean spiking up the EGT and melting the internals of the cat thus making the hc and co numbers spike too??? Have you ever changed your O2 sensor?

[TheNextEpisode]

^Thanks for the info on the Walker cat.

Yeah, I've replaced my O2 sensor in the past.
I just drive carefully. I can get my Cherokee over 30 MPG, so getting over 40 in the Accord isn't too big of a deal.

[Losiracer2]

^ How recently after replacing the cat did you get that smog test?

I don't burn oil (seemingly at all), the oil pan stays clean and dry, and I get no misfires, no CELs, and no soot around the tailpipe. And, like I've said, when I change to a new cat, I pass well under smog requirements. I guess I could be running rich? That would be kinda cool, since I've already been getting 40-45 mpg for the last couple thousand miles.

I guess EGTs could be an issue then, I've been using a wrapped DC header which might be contributing to heat being transferred to the cat.

Well my bumper is still pretty Sooty looking after about a thousand or so miles. I always have to clean it. But I got the emissions tested about 5 months after I got the cat replaced.