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Hi-flow catalytic converters not lasting very long

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Spades

15+ Year Contributor
268
2
Apr 29, 2007
Beaumont, California
Just failed my bi-annual smog test, I passed everything except for HCs at idle, the limit was 100 I got a 133, and HCs was also high @2500 RPMs but passed.

Anyway, about 4 years ago I bought a new Catco 3" hi-flow cat, passed smog the 1st time around with it, and then 2 years later smog time I failed, so I go buy a 3" Magnaflow hi-flow cat and again the car passed fine, well the time has come around again so go to test and it fails. It seems that I cant get over 2 years of life out of these aftermarket hi-flow cats. Does anyone have better luck or longer lasting cats? Im not sure if its my car causing its short life or are aftermarkets cats just not designed to last very long. Id like to keep it legal but I just cant keep buying cats every 2 years. Suggestions? Tips? Advice?.... Thanks!!
 
What you may have to do is use a pipe for daily use and switch to the cat for the test. Walker makes 3" clamps that allow you to but your exhaust pipes together, no welding. Undo the clamps, the pipe will come out and then install the cat.
 
You have any way to tune?? I bet you using dsm link with the proper AFRs the cat will last much longer and you will have an easier time passing emissions. Also using a couple cans of heat fuel deicer helps pass big time as well as its all alcohol. My car passed with no cat using heat treatment and a proper tune.
 
I wonder about those additives they sell over the counter, cant remember the brand but it says things like "guaranteed to pass", anyone try any of those stuff? All my emissions equipment is intact, my 02 sensor is only a year old, my fuel trims are dead on according to my logger, and im getting good gas mileage so id say my car is in pretty good tune...
 
You know, I have had similar experiences with my DSM. My car passed with my 3" cat two years ago and failed the biennial. Granted, NUMEROUS upgrades were made during that period, but heck if the fuel trims line up it should pass, no?

Against tuner sense and even my formal smog education, I had to lean the car past the fuel trim limits to get it to pass. Just last week, I found a small piece of the cat rattling inside my muffler; a little strange considering I drive this car pretty daintily and I've never misfired excessively. Maybe it doesn't like meth.

You could try the metal-core cat converters and see if they last; last I read they don't reduce emissions nearly as much, but they're more durable (for obvious reasons).
 
Hmm meth injection I forgot about that, I am spraying meth and now im wondering if that is whats taking the catalytic out?

BoostFrenzy - I dont believe im running rich as thats the purpose of the o2 sensor to operate on a closed loop system, and my fuel trims are dead on. Plus the fact that I passed the 2500 RPM test and failed HCs only @ idle

And for the seafoam idea, my engine only has about 14K miles on a fresh rebuild, I doubt it will have much to clean out
 
I dunno, the general consensus seems to be that if it doesn't harm O2 sensors it won't harm cats.
 
If you still have the stock downpipe, you should do what I've been doing for the last 4 years. Every time I need to do the smog check , I put in the stock downpipe a month before the smog check, and It always pass,just my .02
 
I keep a good, low mile cat in my closet. It goes on the car just for smog check. For the rest of the year I run the old hi flow cat which still works good enough so it doesn't stink up the air when I'm stopped at a light. Hitting boost regularly will wear out a cat quicker.
 
I wonder about those additives they sell over the counter, cant remember the brand but it says things like "guaranteed to pass", anyone try any of those stuff? All my emissions equipment is intact, my 02 sensor is only a year old, my fuel trims are dead on according to my logger, and im getting good gas mileage so id say my car is in pretty good tune...

Wow this almost became a California discussion. No offense!
Yes you might pass with the guaranteed pass stuff. My nephew used it for his gst which had apexi font mount, intake, apexi bov and an exhaust. Now I don't know if that's rough for emissions but he passed with flying colors!
 
This is why it pays to have friends everywhere... I have some friends at my local lube shop. Nuff said.

I second the idea of just throwing in a cat for a day every 2 years.
 
i agree with pneumo and HIGHPSI4, thats the first thing that came to mind... buy a new cat, but it in got the test, and after put you old cat back in. that way u can pass emissions and it will still be within the law because u didnt know it failed.... right? LOL
 
Are you making sure to get the car really hot before you take it it? Drive it hard for quite a while hitting a lot of boost before you stop to test because a properly warmed up cat will make a big difference. Seafoam never hurts and 14k is certainly not too soon to start. I generally seafoam my cars every year and rarely put more than 10k on either one of them in that time.
 
Are you making sure to get the car really hot before you take it it? Drive it hard for quite a while hitting a lot of boost before you stop to test because a properly warmed up cat will make a big difference. Seafoam never hurts and 14k is certainly not too soon to start. I generally seafoam my cars every year and rarely put more than 10k on either one of them in that time.

Personally I like to get the car really hot by driving on the freeway at normal speeds. I used to have an EGT gauge, and it got just as hot after 20 minutes on the freeway. Hitting boost throws a lot of HC into the cat from the rich AF ratio used at WOT, while cruising on the freeway gets the car hot while staying lean, so it's friendlier to the cat.
 
UPDATE!!!

Went out and bought an OEM exhaust system off a local and smogged again today, the car passed with flying colors!!

Previous test with Hi-flow cat:
HC @ idle was at 130.....limit is 100.......FAIL
HC @ 2500 was 118.......limit is 130.......PASS

Todays test with OEM exhaust system:
HC @ idle was at 19.............................PASS
HC @ 2500 was 11...............................PASS

So there we have it, Hi-Flow cats are nowhere as efficient as OEM cats, no other changes were made to my car
 
In cali do you have to goto the state to get a smog test? If not i think it would have been easier to just goto a gas station and buy an inspection sticker right? Then wouldn't have had to keep buying cats and swaping them out
 
This is why it pays to have friends everywhere... I have some friends at my local lube shop. Nuff said.

I second the idea of just throwing in a cat for a day every 2 years.

:thumb: second on that one, if im just going to take the cat right off again, it pays to know someone who can save you the trouble..:hellyeah:


BTW longjon, I wish it was that easy, Cali is one of the strictest states when it comes to emissions. you can't just go to a gas station and buy an inspection sticker...sh*t i wish :rocks:
 
oh yeah wasn't sure about what the rules were in Cali i knew it was different but damn that sucks LOL in that case it would be good to swap the regular cat in and out for inspection and as for driving a with stright pipes I know in Jersey the cops are very assholish with imports they'll get down and look to see if you have a cat in or not and the fine is like 10k or something crazy like that
 
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