C63 AMG (W204) 2008 - 2015
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Long-Tube Headers with Primary Cats

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Old May 29, 2023 | 01:07 PM
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Long-Tube Headers with Primary Cats

Does anyone here have any experience installing long-tube headers with primary cats?

I purchased these GMA long tube headers, but want to retain either my OEM cats or install 200 cell weld-ins:




My bodyshop said that there isn't enough space in a W204 to retain OEM cats in the long-tube header configuration.

Any feedback from experience (and any pictures) would be greatly appreciated.

Cheers
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Old May 29, 2023 | 04:46 PM
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I added 200-cell cats behind my LTH mostly because the smell was just too much to handle. Plenty of options out there that will fit as long as they're less than 5" in diameter and under 1' long as there's lots of room after the headers before and x-pipe or resonator.
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Old May 29, 2023 | 05:25 PM
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Originally Posted by Accidental L8 apex
I added 200-cell cats behind my LTH mostly because the smell was just too much to handle. Plenty of options out there that will fit as long as they're less than 5" in diameter and under 1' long as there's lots of room after the headers before and x-pipe or resonator.
Thanks a lot! Do the 200-cell cats trigger a Check Engine Light?

Did the O2 sensors require any modifications to get them to be installed further down the exhaust pipes?

Will your car still pass smog without a visual inspection?
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Old May 29, 2023 | 07:08 PM
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Originally Posted by Sentinel83
Thanks a lot! Do the 200-cell cats trigger a Check Engine Light?

Did the O2 sensors require any modifications to get them to be installed further down the exhaust pipes?

Will your car still pass smog without a visual inspection?
My O2 sensors are tuned out since I don't run them due to being SCed with a custom tune.

Adding a set should not trigger a CEL though. These are the same as having secondaries which are after the O2 sensors anyway.

No smog for years here, but doubtful.
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Old May 29, 2023 | 08:24 PM
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Originally Posted by Accidental L8 apex
My O2 sensors are tuned out since I don't run them due to being SCed with a custom tune.

Adding a set should not trigger a CEL though. These are the same as having secondaries which are after the O2 sensors anyway.

No smog for years here, but doubtful.
I appreciate you being so helpful.

After I replied to you I noticed that your picture did indeed show the 200 cell cats being located after the O2 sensors.

Do you see any potential issues with long-term reliability if the O2 sensors were to be tuned-out?

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Old May 29, 2023 | 09:22 PM
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Originally Posted by Sentinel83
I appreciate you being so helpful.

After I replied to you I noticed that your picture did indeed show the 200 cell cats being located after the O2 sensors.

Do you see any potential issues with long-term reliability if the O2 sensors were to be tuned-out?
It's really common to have them tuned out since LTH will theow a CEL otherwise. I've not heard of any issues doing so.
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Old Jun 2, 2023 | 10:58 PM
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I have 400-cell cats behind my MBH longtubes. No secondary cats, aftermarket resonators in place of the stock ones (center section was straight straightpiped when I bought the car).
It's a good, reasonable volume and doesn't smell, but it's still pretty raspy. I will be adding a second pair of short (4" body) resonators tomorrow.
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Old Jun 2, 2023 | 11:04 PM
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Originally Posted by AMGSIXTHREE
I have 400-cell cats behind my MBH longtubes. No secondary cats, aftermarket resonators in place of the stock ones (center section was straight straightpiped when I bought the car).
It's a good, reasonable volume and doesn't smell, but it's still pretty raspy. I will be adding a second pair of short (4" body) resonators tomorrow.
@AMGSIXTHREE sounds like a fantastic setup! Would you please share YouTube videos of before and after the short resonator information?
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Old Jun 2, 2023 | 11:45 PM
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Originally Posted by Sentinel83
@AMGSIXTHREE sounds like a fantastic setup! Would you please share YouTube videos of before and after the short resonator information?
I can do an after. Too late for a before, unfortunately.
It sounds OK, but has a pickup truck glasspack rasp when under load or at WOT. If these little resonators kill it I will post video.
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