Lifetime of a stock cat? - Miata Turbo Forum

johndoe · 06-30-2009, 10:42 PM

Failed emissions again. I'm going to try getting my stock cat's flanges changed to 3" and throwing it in. The only thing is the stock exhaust has been sitting outside for the past year. The cat is still bolted to it so the innards aren't directly exposed to the elements but do you think its effectiveness has been diminished at all because of this?

johndoe · 07-01-2009, 01:44 PM

I'll assume this was a dumb question since no one's answered. Guess I'll give it a shot.

gospeed81 · 07-01-2009, 01:49 PM

I would assume that it wouldn't corrode considering the metals that are used.

**y8s** · 07-01-2009, 01:53 PM

how do you know the issue is with your cat in the first place?

supra441979 · 07-01-2009, 01:59 PM

1995 and below (OBD 1) doesn't have emission here in NC. I'm not sure about other states though.

m2cupcar · 07-01-2009, 02:11 PM

johndoe- throw up your test results

Stein · 07-01-2009, 02:20 PM

To answer your original question, no. Just from being exposed to the elements with the stock exhaust still attached to the end I seriously doubt that it "went bad". The catalyst won't rust.

ArtieParty · 07-01-2009, 02:37 PM

Ask Paul for his emissions passing MSQ. I believe he tunes the timing down for it.

johndoe · 07-01-2009, 02:57 PM

I asked Paul. He said what I had tried, retarding the DIY map by a couple degrees. I still failed by almost the exact same amount. I'll throw up the actual numbers when I get home but essentially I'm passing NOx but failing HC and CO. I'm thinking the cat might help but part of the problem is that the AFR numbers aren't reliable. If I go out and tune it on a hot day it's correct. But then when I turn the car on after it's been sitting the numbers are rich (after it's warmed up to the point where there are no temp related corrections of course) until I've been driving for a while and it's sufficiently heatsoaked. Could this be due to the MAP sensor placement on BEGI's kit that I've been to lazy to ever move? It's been a while since I fucked with it so I'm a bit rusty. I know this is noob shit, I apologize.

johndoe · 07-02-2009, 04:09 PM

Test results:

HC 1.51 gpm Limit: .80 Fail
CO 21.43 gpm Limit: 15.00 Fail
Nox .43 Limit 2.00 Pass

They ran it four times that day. By the third time the results changed.

HC 1.95 gpm Limit .80 Fail
CO 14.39 gpm Limit 15.00 Pass
NOx .93 gpm Limit 2.00 Pass

So help me out here. WTF is going on. Heatsoaked sensor in the intake causing inaccurate AFR readings? Fucked cat? Both?

**y8s** · 07-02-2009, 04:17 PM

I'm guessing you're too rich. NOx goes down as you get richer. CO and HC go up as you get richer. what happens if you remove 10% of your fuel at the test point (rpm/load)? does it still run fine? you may also want to add some timing if the NOx creeps up.

a dead cat would have some of your readings way outta wack. you look pretty close.

johndoe · 07-02-2009, 04:25 PM

That's my guess as well but the gauge doesn't reflect that which is what is making it hard to remedy.

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