Catalytic Converter Question
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UA7_Unknown
Joined: Apr 2018
Posts: 310
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From: Raleigh, NC
Catalytic Converter Question
I had recently picked up headers with a flex pipe and it appears the cat it came with is gutted. I’ve typically either left the OEM cat on or bought a high flow with previous vehicles, so am curious if running this will throw a code on my TL or if I’m better off just buying a high flow as I originally intended?
Thread Starter
UA7_Unknown
Joined: Apr 2018
Posts: 310
Likes: 53
From: Raleigh, NC
Another thing I wanted to add; if it does throw a code presumably for the 2nd O2, it should not impact performance as to my understanding it’s the 1st O2 that measures A/F ration and not the 2nd?
It will very likely throw a code, P0420, for "catalyst efficiency below threshold". I'm well versed with that dreaded code. And yes, you're correct that it won't affect performance. If anything, it will free up flow and give a few extra horsies. However, the catalytic converter also serves to muffle some of the exhaust noise, so you'll experience a different exhaust tone - louder for sure. But with the resonator and mufflers, it's not likely to be overly droney or raspy.
A fix I recommend if you choose to go with a gutted cat or straight pipe is a defouler, which is more or less a spark plug spacer with the center drilled out. You can look up the method on YouTube. That method works about 75% of the time. Expect the occasional code to pop up though. Better yet, if you want to nearly guarantee no problems, get a "mini" catalytic converter dongle like this one:
I don't condone running without a cat though. But if you choose to do so, those are a couple ways you can do it without getting a CEL popping up.
A fix I recommend if you choose to go with a gutted cat or straight pipe is a defouler, which is more or less a spark plug spacer with the center drilled out. You can look up the method on YouTube. That method works about 75% of the time. Expect the occasional code to pop up though. Better yet, if you want to nearly guarantee no problems, get a "mini" catalytic converter dongle like this one:
I don't condone running without a cat though. But if you choose to do so, those are a couple ways you can do it without getting a CEL popping up.
Thread Starter
UA7_Unknown
Joined: Apr 2018
Posts: 310
Likes: 53
From: Raleigh, NC
It will very likely throw a code, P0420, for "catalyst efficiency below threshold". I'm well versed with that dreaded code. And yes, you're correct that it won't affect performance. If anything, it will free up flow and give a few extra horsies. However, the catalytic converter also serves to muffle some of the exhaust noise, so you'll experience a different exhaust tone - louder for sure. But with the resonator and mufflers, it's not likely to be overly droney or raspy.
A fix I recommend if you choose to go with a gutted cat or straight pipe is a defouler, which is more or less a spark plug spacer with the center drilled out. You can look up the method on YouTube. That method works about 75% of the time. Expect the occasional code to pop up though. Better yet, if you want to nearly guarantee no problems, get a "mini" catalytic converter dongle like this one:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I don't condone running without a cat though. But if you choose to do so, those are a couple ways you can do it without getting a CEL popping up.
A fix I recommend if you choose to go with a gutted cat or straight pipe is a defouler, which is more or less a spark plug spacer with the center drilled out. You can look up the method on YouTube. That method works about 75% of the time. Expect the occasional code to pop up though. Better yet, if you want to nearly guarantee no problems, get a "mini" catalytic converter dongle like this one:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I don't condone running without a cat though. But if you choose to do so, those are a couple ways you can do it without getting a CEL popping up.
I thought I read here, somewhere, that if you are not supercharged or turbocharged a hi flow cat would only hurt your performance being normally aspirated? Something about losing back pressure when running headers.
Last edited by zeta; Oct 18, 2019 at 11:11 AM.
Instructor
Joined: Aug 2015
Posts: 130
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From: San Francisco, CA
I had recently picked up headers with a flex pipe and it appears the cat it came with is gutted. I’ve typically either left the OEM cat on or bought a high flow with previous vehicles, so am curious if running this will throw a code on my TL or if I’m better off just buying a high flow as I originally intended?
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Thread Starter
UA7_Unknown
Joined: Apr 2018
Posts: 310
Likes: 53
From: Raleigh, NC
Much appreciated. I'm actually buying a Magnaflow next week just in case this experimental gutted cat doesn't fit my taste. Thanks again for the input!
Instructor
Joined: Aug 2015
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From: San Francisco, CA
Thread Starter
UA7_Unknown
Joined: Apr 2018
Posts: 310
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From: Raleigh, NC
Going to buy a replacement CAT as the OEM one was bad regardless and with it gutted I don’t like the sound; don’t feel like messing with mufflers or anything to fix the noise either. What aftermarket CATs do you guys recommend?
Instructor
Joined: Aug 2015
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From: San Francisco, CA
I have Magnaflow lol. Passes smog every time (I live in California so emission laws are strict af).
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