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Resolved Three way cat converters..?

  • Thread starter Thread starter PonyGTrider
  • Start date Start date Nov 2, 2025

PonyGTrider

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#1
  • Nov 2, 2025
  • #1
Hi all,
Out of curiosity have any of you used universal three way cat converters?

My ride has no anti-smog system anymore. I removed the lower cat converters and later on I got rid of the upper ones but the exhaust fumes were extremely obnoxious so I put the uppers back in there.
I’ve read that you don’t supposed to run the lowers without fresh air from the air pump.
What I’m trying to get is a less stinky exhaust so the questions I have are, will those universal three way cat converters work fine without any air injected in them???? Will they last???? Will those cats reduce or eliminate most of the bad fumes coming out of the tail pipes???
Has anyone tried them or currently have them installed with good results?

Thank you much
 

nickyb

I gotta say i never painted my nuts, Never Ever
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#2
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You can run new cats without issues.
 
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Noobz347

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#3
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I have 3-way cats.

They work as well as the OEM 2-way with the air pump.

The rest of my exhaust includes:

Anderson/Bassanni 1-7/8 unequal shorty headers
Dr. Gas X with 3-way cats
Bassanni Quiet Thunder cat-back
I've had this system installed since the early 2000s

While I was active duty, I had no issues passing smog in states that had sniffer checks.

This system will of course, not pass Cali's visual inspection (but neither will a lot of the I have under the hood).
 

PonyGTrider

5 Year Member
Feb 27, 2019
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#4
  • Nov 2, 2025
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nickyb said:
You can run new cats without issues.
Click to expand...
You mean the original cats? I read that the downstream cats will get clogged y there is no fresh air supply…

Thank you
 

nickyb

I gotta say i never painted my nuts, Never Ever
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#5
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No , new cats. The new cats don't need air pumped into not them.
 
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PonyGTrider

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#6
  • Nov 2, 2025
  • #6
nickyb said:
No , new cats. The new cats don't need air pumped into not them.
Click to expand...
I’ll try installing them and see if the smell goes away.
Thank you
 

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
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#7
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I feel like there is a contradiction in terms going on.

2-way cats are like the OEM cats. There are two pre-cats and two after-cats. These systems require air to function correctly.


3-way cats are the newer style. You only need one per exhaust tube and they do not require an air pump.


If you are planning to reinstall the OEM cats, I would suggest including an air pump. You don't need all the valves etc. It can just pump air straight the secondary cats. Normally, the EEC would only pump air to the cats before they are heat soaked.
 

PonyGTrider

5 Year Member
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#8
  • Nov 2, 2025
  • #8
Excelent description, I’ll follow your suggestions.
Thank you
 
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