P0421 ND Supercharged fried cat?

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P0421 ND Supercharged fried cat?

Postby ChanceS905 » Thu Jul 05, 2018 7:11 am

Just leisurely driving home from seeing fireworks last night I get an engine code. Read it this morning and its P0421, faulty catalytic converter. Less than 500 miles since the supercharger install. Checked the other forums and they are all saying its fried and edelbrock is "working on a solution". Awesome... Puffs smoke as well if I accellerate even a little hard. How do I address myself without breaking the bank and avoid it again later? CARB tune, not raced and 4 mile commute (warmed before every drive) Very frustrated. Wife is going to kill me :?
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Re: P0421 ND Supercharged fried cat?

Postby Brian » Thu Jul 05, 2018 12:34 pm

Here in CA must run the stock header, but if not in a state doing actual checks then a performance header will give more power and never have an issue. My wife's car is original install and still running without cat issues, Edelbrock even borrowed her car back for more test and tune with an eye to watching that cat health and still found no threat to converter on her car.

Your purchase is so recent that I assume you already have Edelbrock's latest tune, which is not supposed to have cat issues. My best guess on why some customers have issue and some don't, is that the Ecutek software that loads the tune is somehow more successful in some cars than others...but that's pure guess (Edelbrock might be able to shed more light on that). This is one of those times an O2 wideband log would help a lot, suggest you contact Edelbrock and LOG the car on current tune and see if you can find it going pig rich/too lean somewhere in normal driving.
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Re: P0421 ND Supercharged fried cat?

Postby ChanceS905 » Thu Jul 05, 2018 2:43 pm

The cat is definitely going theres ashy stuff in the tail pipe. Edelbrock is going to take a look @ my log once the tune guys are back from vacation. Is your midpipe flange position where it would be stock? I know it's meant for your superstreet .I'd like to get it and just weld a flange or v-band on my axle back since I only put it on a month ago (cobalt). That way later when I have more $ (and a not so irritated wife) I can opt for your standard length header.
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Re: P0421 ND Supercharged fried cat?

Postby Brian » Thu Jul 05, 2018 3:13 pm

That 'ashy' tailpipe sure sounds like something is off, not getting that on my wife's supercharged ND or mine.

Yes, our MaxMidpipe has flanges in stock locations, will bolt to Cobalt muffler, and has O2 connections in it already for putting a wideband for logging (you will end up using these connections for stock O2 sensors once header is added but before that happens a wideband can use one of them). On my race use ND with the supercharger we added a third O2 bung to MaxMidpipe for AEM Wideband longterm use.

Might also inspect and upgrade plugs, we are using Brisk Racing P8 1626 in our race ND with supercharger, same gap as they come out of the box.
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Re: P0421 ND Supercharged fried cat?

Postby ChanceS905 » Mon Jul 09, 2018 6:07 pm

I replaced the plugs a couple weeks ago per you reccomendation. Cat has completely melted down and the car is not happy at all, undrivable. Ordering your header and mid pipe tonight. (Horray another $1000!) :evil:
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Re: P0421 ND Supercharged fried cat?

Postby Brian » Mon Jul 09, 2018 6:17 pm

No other codes, no engine misfires right? No track use? I went to Edelbrock today, had lunch with them and mentioned your car. They suspect something not right somewhere else in the install. We did have a customer who reported engine misfire and he thought it was the tune, he posted at Miata.net that he thought the issue was the tune, but in his case actual engine misfire suggested something else was off, he checked some other details and found broken wire to ignition coil that caused intermittent miss (he was regularly on 3 cylinders). The Edelbrock guys also mentioned there is another calibration update that just came available. I have a much older version in ours, but will try the latest. I suggest you too reach out to Edelbrock Calibration for updated version.
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Re: P0421 ND Supercharged fried cat?

Postby ChanceS905 » Mon Jul 09, 2018 7:25 pm

No misfire just the cat code. Does not seem to misfire. smooth at idle as well as running even with the code, though a bit sluggish. I heard the faintest of pings pulling out of work now the exhaust is VERY quiet now and its bogging down like it's being choked. Still yet no obvious misfire or rumbling with throttle or at idle. I put my hand over the exhaust and it feels like someone blowing through a straw instead of the patting of air that should be there.. I dont know what else could be wrong with the install. Anything I can think of would have thrown a code, evap, vacuum, map etc.
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Re: P0421 ND Supercharged fried cat?

Postby Brian » Fri Jul 13, 2018 5:07 am

You should have the new parts any day now. Obviously we don't want to immediately melt down the new cat in the midpipe, once car running with new parts let's do immediate log for Jason at Edelbrock. Do you know how to use the Ecutek to log with computer as you drive? If not, call and talk with Sean in our shop and he can get you setup on that and get you Jason's email at Edelbrock for review of the log, etc. I have sent our man Sean an Email this morning (he won't be in shop for a few more hours), asking he coordinate with you on the log for review of it, and getting it to Edelbrock, etc.
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