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Thread: How do I cheat the O2 sensor if I remove my cat?

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    Senior Member NuuTuuVeeDubb is on a distinguished road NuuTuuVeeDubb's Avatar
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    Default How do I cheat the O2 sensor if I remove my cat?

    Hi all, my cat is beginning to clog and I have no interest in replacing it since I live in wisconsin and there is no emission testing here. My question is what do I do about the O2 sensor? There is only one and it is on the cat, any help would be much appreciated!

  2. #2

    Default Re: How do I cheat the O2 sensor if I remove my cat?

    Depends on the year of the car, Pre-OBD2 cars have only 1 or 2 max and are needed to maintain the air/fuel ratio. Post OBD2 cars can delete the one past the Catalytic Converter since it only monitors CC efficiency using a "o2 sensor simulator" or a ECM chip like the one from BFI.

    Depending on location this may be illegal, what you do with the info is up to you.

  3. #3

    Default Re: How do I cheat the O2 sensor if I remove my cat?

    i was also wondering the same thing, i have a 98 jetta. how do you know if your car is pre or post OBD2 ? and im guessing the oxygen sensor stimulator is COmepletly nessacary

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    Senior Member tatsu is on a distinguished road tatsu's Avatar
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    Default

    Anything older the 94 or 95 is obd1 98 is obd2 for sure

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    Stacks on deck. ChaseO is on a distinguished road ChaseO's Avatar
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    Default Re: How do I cheat the O2 sensor if I remove my cat?

    you can get the J-pipe also as a quick fix.

  6. #6

    Default Re: How do I cheat the O2 sensor if I remove my cat?

    so it wouldnt really hurt it To remove my cat basically ? if i get the new sensor

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    Senior Member NuuTuuVeeDubb is on a distinguished road NuuTuuVeeDubb's Avatar
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    Default Re: How do I cheat the O2 sensor if I remove my cat?

    I've got a 95 and there is only one sensor on the top of the cat in the front (engine side) since it is before the cat technically does anyone know if I could just replace the cat with a pipe and and cut a hole in it for the sensor?

  8. #8

    Default Re: How do I cheat the O2 sensor if I remove my cat?

    You can relocate the O2 sensor to anywhere where there is a single pipe (ie. if you run a header you can't just tap into the #1 cyl pipe).

    Removing your Catalytic converter is pointless, in most cases, no power will be gained running street grade fuel. Get a universal High Flow Cat from Jegs ($100 last time I bought one) for the pipe size and then sawzall the old one out and clamp the new one in or weld it if you can.

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    Senior Member NuuTuuVeeDubb is on a distinguished road NuuTuuVeeDubb's Avatar
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    Default Re: How do I cheat the O2 sensor if I remove my cat?

    I'm not doing it to gain power, I'm doing it because it's clogged lol, it's not plugged or anything but it's getting there. I live in Wisconsin and they don't do emissions testing here so I'm just trying to save money by welding in a pipe with the same inside diameter as the existing pipe. My concern lies in what to do with the O2 sensor? By my thinking and what blackspyder said I should be able to put a bung in the new pipe and place the sensor there?

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    Stacks on deck. ChaseO is on a distinguished road ChaseO's Avatar
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    Default Re: How do I cheat the O2 sensor if I remove my cat?

    have a bung welded in, and use a $30 j pipe...
    it extends your O2 senser into a position that it wont read that its not working right.

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    Junior Member Kkowalski92 is on a distinguished road Kkowalski92's Avatar
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    Default Re: How do I cheat the O2 sensor if I remove my cat?

    You should be able to weld in a new pipe and just use a threaded plug that will match the threads to the o2 sensor. You will most likeley run richer due to the fact that the cat will no longer be there, and oxygen readings will increase(thus telling the PCM to dump more fuel, it may pop the code still. It's still better than no o2 sensor though. In the long run I think replacing the cat is worth it for these reasons:
    -Less gas used
    -less o2 sensors replaced from fouling( due to rich air/fuel mixture)
    - no codes poped (although it's possible that doesn't happen)
    - other things that I may not be able to explain
    I hope I helped a little bit, but that's what my opinion is

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    Senior Member Sallad is on a distinguished road Sallad's Avatar
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    Default Re: How do I cheat the O2 sensor if I remove my cat?

    Quote Originally Posted by blackspyder View Post
    Removing your Catalytic converter is pointless, in most cases, no power will be gained running street grade fuel.
    I disagree. The cat is a HUGE restriction. Why do you think they created HI-Flow cats?

    As for your comment on "street grade" fuel. Not sure what you mean by that. If you are talking about higher octane fuels, then, no power is gained by running higher octane fuel. Octane prevents pre-detination, so you can run a higher compression or more advanced timing. That creates the power, the octane allows the fuel to not burn before the spark is created.


    Quote Originally Posted by ChaseO View Post
    have a bung welded in,
    This

  13. #13

    Default Re: How do I cheat the O2 sensor if I remove my cat?

    Strictly from my personal experience I dyno'd my 98 4.3L S10 back in 03 with and without the Cat, HP was the same (148HP at the wheels) both times. High flow Cats prevent clogging when running rich, some vehicles might gain 1-5HP but it's a crap shoot.

    As for the "street fuel" comment, regular Cam2 or whatever you call the pretty smelling race fuel where ever you are has a tendency to clog Cats even high flow ones.

    Weld a bung in.

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    Senior Member Sallad is on a distinguished road Sallad's Avatar
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    Default Re: How do I cheat the O2 sensor if I remove my cat?

    Quote Originally Posted by blackspyder View Post
    As for the "street fuel" comment, regular Cam2 or whatever you call the pretty smelling race fuel where ever you are has a tendency to clog Cats even high flow ones.
    Oh, you are talking about actual racing fuels. Ok, I didn't know you meant those. Sorry.

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    Senior Member Green '95 is on a distinguished road Green '95's Avatar
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    Default Re: How do I cheat the O2 sensor if I remove my cat?

    If the car is OBD I you can remove the cat with zero changes to the way it runs. The sensor just has to be there to regulate the air/fuel mix. If you have a OBD II car you have to have both sensors in it to get no codes. The first sensor regulates air/fuel mix and the second is there to check the cat is doing its job. There are several ways around the second sensor. One would be to buy a bypass box to plug into the wire harness or you can measure resistances and solder in a resistor so it reads correctly.

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    Senior Member NuuTuuVeeDubb is on a distinguished road NuuTuuVeeDubb's Avatar
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    Default Re: How do I cheat the O2 sensor if I remove my cat?

    Thanks to all! Green 95, it is an OBD1 with just the one sensor, if I remove the sensor entirely won't that throw a code? And if it's there to regulate the air/fuel mixture how good will the engine run without it there? I would love to be able to just eliminate it so I could just weld in a pipe but I wonder how crappy the car will run as a result of doing that? Thanks!

  17. #17

    Default Re: How do I cheat the O2 sensor if I remove my cat?

    Quote Originally Posted by NuuTuuVeeDubb View Post
    Thanks to all! Green 95, it is an OBD1 with just the one sensor, if I remove the sensor entirely won't that throw a code? And if it's there to regulate the air/fuel mixture how good will the engine run without it there? I would love to be able to just eliminate it so I could just weld in a pipe but I wonder how crappy the car will run as a result of doing that? Thanks!
    If you remove the 02 sensor it will throw a code, engine will run like crap, and might even go into limp mode. Well you could just weld a pipe there, but just mount the 02 sensor at the same spot where the old one was(same distance from the engine).

  18. #18
    Senior Member Green '95 is on a distinguished road Green '95's Avatar
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    Default Re: How do I cheat the O2 sensor if I remove my cat?

    OBD I car you have to have the O2 sensor. I said you can remove the cat with no change in the way it will run. There is no sensor after/in the cat to tell the computer that it is working properly.

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