high flow cat and o2 bung placement on new mid pipe

[davemiller78]

hi guys.i know this is probably a noob question,but i got to ask lol. i just got done picking up a cat-less header and cat-less mid pipe. i plan on installing a high flow cat on the mid pipe as well as a o2 bung (dont want to mess with anti-fouler). my question is how far from the cat should i put the o2 bung?or does it even matter? thanks for any info you guys can give me on it.

[navylife59]

The reason for the anti-fouler/MIL eliminator, is that the primary three-way catalytic converter is mounted in the OEM header just after the Bank1Sensor1 wideband O2 sensor. The Bank1Sensor2 narrowband Heated Oxygen Sensor is located in the s-pipe (front exhaust pipe) and the secondary TWC cat is located at the beginning of the mid-pipe (center exhaust section) along with the OEM resonator. When you remove the primary cat, you are causing the reason for the MIL. The secondary cat has no function with the O2 sensors so it can be removed w/o any change to the ECM.

Exhaust Diagram
http://www.club-tc.com/forums/tc-kno...omponents.html

Understanding what cause the MIL to illuminate and the reason for the anti-fouler.
http://www.club-tc.com/forums/tc-kno...nsors-mil.html

[davemiller78]

thanks for the info navy...so since the only cat i am going to have is the high flow one i am putting on the mid pipe its better to use the anti-fouler rather than moving the 2nd o2 down to the mid pipe just after the new cat?i am cool with doing it either way,its just that whatever way i end up going i just want it to work.dont feel like crawling under the car mad times lol.

[navylife59]

Both sensor are calibrated in a paired relationship. The 2nd sensor acts as a control to measure the performance of the primary sensor and provides data for the ECM to fine tune the A/FR and fuel enrichment/de-enrichment. Putting the 2nd sensor after the highflow cat in the mid-pipe might possible work, but it will be so far it's calibrated position that the readings will be skewed. The ECM in-turn may start adding error correction values because it thinks the primary sensor it off. You can try it and if it does not work, just put it back to it's original location. You will find, however, that the wiring harness is going to be way short.

[davemiller78]

thanks for all the info.it seems i got some food for thought.as it stands i am either going to keep the CEL eliminator.i got a dc sports CAI,megan cat-less header,2.5 inch down pipe.i got a 2.5 inch cat-back off ebay and threw the muffler section out lol and put a borla muffler section on.went catless for a few days just to see what it was like,but i plan on throwing the high flow cat and a thrush glasspack on the mid-pipe this week.thanks navy for helping me out.the info you just gave me is what i have been trying to find out.