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Technical question: why exactly do weak coils kill cats so fast?

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Old 11-20-2014, 10:10 PM
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Technical question: why exactly do weak coils kill cats so fast?

So I recently changed my ignition from a dead OEM system to BHR and the next item on my repair list is a new cat. I've already decided on the BHR midpipe with cat because Washington requires emissions every 2 years and I can't pass with P0420 lit up. And there is no way in hell I'm paying $2k+ for an OEM cat. That's just ridiculous.

So just to understand the RX-8 better, I was hoping a techie could explain to me why weak or dead ignition coils kill cats so fast?
Old 11-20-2014, 10:31 PM
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With weak coils fuel doesn't burn. Unburnt fuel reacts with the cat and burns. Too much fuel in the cat will cause it to over heat and melt.
Old 11-21-2014, 12:06 AM
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Great, thanks. That would explain why it smelled so rich when I bought it and why it smells so much better after changing the coils.!
Old 11-21-2014, 09:10 AM
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Note that ANY cause for excess unburnt fuel does the same thing. running rich, coils, plugs, wires, grounding points, maf, ess, vacuum leak, o2 sensor. even overfilling the oil can.

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Old 11-21-2014, 04:09 PM
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I know for a fact the cat is dead, and I'll be ordering a BHR midpipe with cat in the coming week. Compression testing is on my list to do, but first I need to find a place around Seattle that even offers it. The Mazda dealers have yet to even call me back and a Google search returned nothing.
Old 11-21-2014, 06:16 PM
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Any licensed Mazda dealer should be equipped to do a rotary compression test. If you get nowhere with Seattle area Mazda dealers, contact MNAO Contact Mazda - Mazda USA -
Old 11-23-2014, 02:15 AM
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Awesome, thanks.
Old 11-23-2014, 11:44 PM
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UMazda on Roosevelt and 45th just east of I-5
Old 11-24-2014, 11:48 PM
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Originally Posted by TANKERG
UMazda on Roosevelt and 45th just east of I-5
Thanks but I prefer to stay out of Seattle if I can. Crappy roads do not play well with nice cars.
Old 12-02-2014, 12:24 PM
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Originally Posted by EpikYummeh
I know for a fact the cat is dead, and I'll be ordering a BHR midpipe with cat in the coming week. Compression testing is on my list to do, but first I need to find a place around Seattle that even offers it. The Mazda dealers have yet to even call me back and a Google search returned nothing.
Will the CAT installed inside the BHR pass emissions? If so, Charles maybe you can answer this - is there a way to buy that part separately?

I didn't do it at the beginning, but had to throw the OEM cat back on for emissions (still running into other problems x_x) but now just have the midpipe sitting out of my car.

So, I am debating if I should have a shop install the BHR cat onto the midpipe or sell it sadly.
Old 12-02-2014, 06:53 PM
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I already contacted Charles, he said his catalyst will clear P0420 codes.

I'm not sure if his catalyst will fit other midpipes, however. That's a question for him to answer. Remember you can always email him at charles@blackhaloracing.com.
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