Ok, I couldn't really find any solid info here on-site, so here goes:

I've got a stainless steel Megan Racing header on my mini-me swapped Civic (so an EX exhaust setup).
There is a single bung for the Primary O2 sensor in cylinder 4's downpipe as well as a bung at the end of the 4-2-1 dowpipe.
My question is, which is the better location?
The one closest to the header so it'll heat up faster?
Or the bung at the end of the downpipe so it'll read fuel/air data from all 4 cylinders instead of just cylinder 4?
And no, the second bung isn't for the secondary O2 sensor, that one is plugged into my cat. ^^

Anyone else have any experience with this?

I've been running the O2 sensor in the lower bung with a wire extension kit for a few months, but I didn't know if the longer wires caused more resistance/throw off readings/etc compared to the stock position in the header.

Just wanna know if the lower bung is better because it reads all 4 cylinders or if the higher one is better even though it only reads 1 cylinder's data.
Thanks H-tech!
:3

 

I would imagine you are best leaving it where it is so it is reading all 4 cyl vs just 1. I am curious to know myself because I am about to add a wideband but not sure where to have it added.

 

lowest point possible after the collector... most accurate data...

 

Alrighty so I'll leave it where it is!
(now I don't have to crawl under the car and move it XD; )
*shot*
Thanks folks!
:3

 

keep it where it is.
especially for whoever was getting a wide-band. it'd be horrible trying to get A/F ratios off of only one cylinder.

 

Kinda weird that the stock O2 sensor in the EX manifold seems to only read off of one cylinder, #3 to be exact...
Why do you suppose they did that?
oO