Quick Question On 02 Sensors

[hl0m4n]

the e92 m3 has x4 02 sensors total correct? x2 on the headers and another x2 on the xpipe?

if one were to get catless headers and just use the x2 02 sensors on the xpipe any problem?

what about vice versa use header 02 sensors but eliminate the xpipe ones?

thanks guys.

[FStop7]

serch

[J08M3]

You need all 4 O2s

[JuniorDee]

Get this. I bought and installed the AA x-pipe w/o the software. After about 3 weeks I threw the CEL "increased emissions". I bought an ECU code reader from amazon. I plugged in the reader, cleared the error code, and it hasnt come back yet. Its been 2 weeks since i cleared the code. If it comes back then I will just clear it again. No big deal. The ecu reader cost $180.

[J08M3]

^--interesting. are you using and cats?

[JuniorDee]

no cats here, I bought the race x-pipe

[askiles]

You have to use all (4) O2 sensors, or your computer might freak out.

-Andy

[JuniorDee]

yes, use all 4. I am using all 4

[King Tut]

You don't have to use all 4. Please be knowledgeable if you are going to post absolutes. The front 2 O2 sensors on the header are the ones used to adjust your fuel trims based off how lean or rich you are running. The rear 2 O2 sensors are solely used to test how well your cats are working. If you don't have cats this will throw a CEL which you can continue clearing or just ignore. It won't affect how your car is running. You can not remove the front 2 O2 sensors.

[askiles]

The front 2 O2's are not in the headers, they are in the midpipe, just right at the front cats. Are you positive that without the 2 rear sensors, your car will not adjust fuel to be in a somewhat "limp" mode. Not actually in limp mode, but just not running to full capability? I would imagine that the ECU would have to try and compensate for high emissions levels.

You DO in fact have to run the rear O2's, if you do not want a CEL. That is an absolute that is true.

-Andy

[J08M3]

Originally Posted by King Tut

You don't have to use all 4. Please be knowledgeable if you are going to post absolutes. The front 2 O2 sensors on the header are the ones used to adjust your fuel trims based off how lean or rich you are running. The rear 2 O2 sensors are solely used to test how well your cats are working. If you don't have cats this will throw a CEL which you can continue clearing or just ignore. It won't affect how your car is running. You can not remove the front 2 O2 sensors.

Correct, but you wont' pass inspection without them.

[askiles]

You should if you have an ECU tune.

-Andy

[King Tut]

Originally Posted by askiles

The front 2 O2's are not in the headers, they are in the midpipe, just right at the front cats. Are you positive that without the 2 rear sensors, your car will not adjust fuel to be in a somewhat "limp" mode. Not actually in limp mode, but just not running to full capability? I would imagine that the ECU would have to try and compensate for high emissions levels.

You DO in fact have to run the rear O2's, if you do not want a CEL. That is an absolute that is true.

-Andy

I should have said pre cat and post cat instead of front and rear I guess. It is my understanding all the ECU does is look at the value from the pre cat and the post cat O2 sensors, find the difference, and if that value falls outside of the expected range for a long enough period of time it throws a CEL telling you "Hey idiot your cats aren't working properly". I haven't heard of anyone going into limp mode because of this. As for inspection you definitely won't pass with a CEL on or without any cats in your exhaust. That is not something I have to worry about in Florida.

[King Tut]

Originally Posted by askiles

You should if you have an ECU tune.

-Andy

Not if that inspection includes emissions testing. There is no way you will pass without cats and even high flow cats might not be good enough for the sniffer.

[J08M3]

Originally Posted by askiles

You should if you have an ECU tune.

-Andy

Nope, cause they perform a readiness test and that checks to make sure all sensors are working and you will not pass that part.