Is my catalytic blown? - LotusTalk - The Lotus Cars Community
 
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post #1 of 5 (permalink) Old 10-24-2017, 08:37 AM Thread Starter
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Is my catalytic blown?

The car had P0420 code before and taken cared by an eliminator spacer on the 2nd 02 sensor. Maybe it's a sign that the cat is about to go...

So after taking the car to a few track days, I found a noticeable rattle from the exhaust. The rattle sounds like tiny metal pieces hitting, and the rattle appears whenever the rpm raise or drop while in gear, but goes away when rpm is held by steady gas.

I had the rear diffuser removed and found everything secured and no heat shield touching the exhaust; however, I can hear the tiny metal pieces sound when I hit the exhaust pipe.

Any guess? Could this sound be normal for the honey mesh inside the catalytic become melted or broken?

Sam
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post #2 of 5 (permalink) Old 10-24-2017, 08:58 AM
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Sounds exactly like the cat shed its internal bits. Upgrade time!

"Lots Of Trouble; Usually Serious"
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post #3 of 5 (permalink) Old 10-25-2017, 09:20 AM
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I've lost two cats in precisely the same way. Sounds like crap rattling around, because that's exactly what it is. The cat honeycomb breaks, and gets spat into your muffler. It takes a hell of a long time to shake it out of there too, and I could never get all of it out.
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post #4 of 5 (permalink) Old 10-26-2017, 12:26 AM Thread Starter
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Thanks guys, the metallic rattle/buzz pretty much follows the rpm raising to all the way ~6k rpm until the engine sound takes over the cabin, and reappears when the rpm drops while the car is under load (without stepping the clutch.) And it is quite loooooud!

However, to my surprise, while on the way driving to the shop today, the metallic rattle gone!! Gone without a trace! I can highly suspect that it is due to the honeycomb bits settled themselves. I'm not 100% sure, but I have pretty much gone through all the research below:

https://www.lotustalk.com/forums/f101...ce-all-104385/
https://www.lotustalk.com/forums/f101...-sorte-101988/
https://www.lotustalk.com/forums/f259...exhaust-99722/
https://www.lotustalk.com/forums/f101...r-buzz-103260/
https://www.lotustalk.com/forums/f259...00-rpm-113727/
https://www.lotustalk.com/forums/f101...21/index4.html

I hope that it is just cat for me, and it stays that way. But the links above are worthy for everyone who has rattles/buzz to look into. I welcome myself to the Lotus rattle traditions ;p

Sam

Last edited by RGB; 10-26-2017 at 12:32 AM.
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post #5 of 5 (permalink) Old 10-26-2017, 04:17 AM
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I just have a habit now of walking around the car once rapping on the undertrays and diffuser with my knuckle. If it thuds, it is good. If it rattles, it'll only get worse.

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