Mid-Atlantic Sentras

i was wondering wat o2 sensor i have to put a spacer on. i am gettin the megan 4-1 header and it has 2 o2 sensor bungs and it comes with the o2 spacers. just wondering does the qr25 have 2 o2 sensors on the header. i didnt think so.

so would i have to space the o2 sensor on the header or the one by the main cat?
and also wat hole to i out the sensor in on the header?
one hole is up right after the collector and the other one is down at the bottom

on your car there are 2 O2 sensors, both on the header.
you need to put the spacer in the lower one.

you need to put it on the second o2 sensor

reason why is because you want that sensor to think that the air passing through it is cleaner than that of the first one.

hmm sounds like a repeat of another post you made recently.

just the facts man just the facts

+1...if you spaced out the first sensor you'd run ignorantly rich lol That one measures the exhaust to determine your A/F ratio . Second one just monitors catalyst efficiency, which you don't want to read.

I've had mine on for like 55k now $5 fixes ftw! lol

it works even better if you have a bung on your midpipe

ok thanks alot guys. answered my question. n the header im gettin comes with 2 o2 spacers. im gettin it from markspecv

it shouldnt come with 2....
if it does sell one. you only wanna space the lower one.

02-03 model headers come with 2 bungs on the header

04-06 model headers come with 1 bung on the header because their second one is behind the 2nd converter

For instance I have a 04-06 header with a megan racing midpipe which has my second o2 sensor bung, and that is where it is installed. It works better that way because the air takes alot longer for it to get to it, not to mention the fact that it is farther from the exhaust port on the engine. So the air passing through it is in effect cleaner because the carbon count will be significantly less. You still need a spacer to get check engine light to go off.

yea. im gonna see if the spacers are welded on which i dont think they are. so i will prolly sell one