Custom exhaust - spacing of 2nd o2 sensor after rear cat? (1 Viewer)

[jcardona1]

Hey folks - how important is the spacing of the 2nd o2 sensor after the 2nd cat?

I'm looking to run a short exhaust outside the frame using the Magnaflow y-pipe/front cat + Magnaflow universal rear cat. I then plan on running a short exhaust pipe with the smallest muffler I could find so it all fits outside the frame rails and before the rear tire.

In the factory configuration the exhaust curves under the frame and that's where the 2nd o2 sensor is. Since I have less room to work if I want to keep this in front of the rear tire, can I put that 2nd o2 sensor a bit closer to the rear cat?

Based on what I recall it looks like there's about 10-12" of tubing in between the 2nd o2 sensor and rear cat...

 

[cjmoon]

Shouldn’t really matter for rear o2 it’s just there to throw codes if the cat isn't working

 

[nukegoat]

Should be fine

 

[Douglas S]

Rear 02 is emissions only. Space it out with a spark plug non fouler and you could run catless with no codes.

 

[inkpot]

Too bad you can’t get away with a single 3 way cat like this. Short enuff that I can place the 2nd ox sensor at the normal position behind the last cat. This one crosses over frame easily in the early 93-94 position so would leave plenty of room for a small muffler straight back.

 

[inkpot]

 

[landtank]

I put a 3 way cat in and went over the frame as well. Stuck the 2nd sensor about 6" from the cat and it's been fine.

 

[inkpot]

I put a 3 way cat in and went over the frame as well. Stuck the 2nd sensor about 6" from the cat and it's been fine.

Now ya made me go look at mine cause I couldn’t remember exactly where mine is, duh! Looks like it is nearly 2 feet back from the 3 way cat. No codes, 100% pass on smog testing 4 times so far.