Tony @ MPH

Hey guys,

When installing a wideband O2 sensor, where "should" you place it, and where "could" you place it? I have heard that in front of the cats gives you the best idea of true A/F. But at the same time, every time my car has been on a dyno, they are using a tailpipe sniffer to read A/F. Tuners also tune against that signal which has to be much less accurate than a wideband O2 actually in the pipe, right?

So if tuners can tune based on that signal, is there any good reason to NOT weld the wideband O2 bung post-cats (maybe near the X in my LGM x-pipe)? I'd really rather not pull my headers off the cylinder head just to get my wideband O2 up and running, unless I will get a useless signal by putting the sensor post-cats.

'06 Quicksilver Z06

I had a bung put into the driver side header. In front of the cat of course. I have always heard that this is the best place to get the reading.

No need to take the header off. The car was put on a lift and the o2 bung placed.

Dan_the_C5_Man

I have one mounted in the stock H-pipe, just after the header/ H-pipe joint, before the cats, of course.

Tony @ MPH

Hmmm.. I guess nobody's going to jump in and say "behind the cats is perfectly OK!"?

supercoupe01

Would be nice to know, I'm about ready to purchase one. TTT for ya.

5 Liter Eater

I have always heard you want it as close to the header as possible. Also be sure to weld it at an angle between 10'o'clock and 2'o'clock so it doesn't collect water/etc.

Tony @ MPH

I just called LG Motorsports and found out my cats are actually supposed to be AFTER the X-pipe. Right now they are sitting right after the header. If I move the cats back after the X-pipe, I can weld an O2 bung in the X.

This will make the job TREMENDOUSLY easy. I can just take the x-pipe off the car and drag that to a shop that can weld, instead of going some place that has a lift, can weld, and knows what they're doing on the car. Or worse yet, having to remove the header from the cylinder head.... NOOOOOOOOO!

Mike Mercury

here is where I placed mine:



Pass. side... just in front of the pre-cat. Keep in mind that I do not run the WB continiously... just for tuning, then I take it out.

Dope

The LG cats are supposed to be BEHIND the X pipe? That sounds like it would make for really crappy cat performance, being that far away from the engine.

Dope

BlueDragon

Nope they work good there! The new Random Tech 3" Cats work at a lower temp and moving them the other side of the X give you a little better TQ range. I had mine in both locations and moving to the back is just fine.

Dope

So how exactly did you test the performance of the cats in the 2 locations? Did you get the emissions tested back to back?

Dope

Bink

Wow, it helps with torque??? Hadn't heard that. When I put mine back on I'll put 'em aft.

BlueDragon

Yes and with before and after dyno pulls. I have a garage.

With the LG and the cats in front of the X pipe the TQ came on like gang busters after 3K RPM and for auto X and my 2:73 rear I needed more low end TQ. Lou and the guys recommended moving the cats back. I asked the same questions as you. I had one of the first sets of the LG long tubes that Lou shipped. I have about 9000+ miles on them street and track. I don't think I will pass any noise test I have the full 3" system breathing through a early Corsa Indy system and believe you me it is loud at WOT. Not bad at Cruise or Idle.

I am in Calif. so I need to be legal. However you can get most well tuned cars to pass test with the engine at operating temp without cats. So for those of us running well tuned cars with good A/F ratios the visual is the most important part of passing.

I am wating on my HP Tuner Wideband as we speak right now the only way I ahve been doing a ratio check is with an emissions tester. I have been doing that for years. I admit it is not accurate as there is pencil work involved and some guess and think, but that will be over with the WB.

BlueDragon

Careful, I did not say more TQ, I said it changed the curve! Lou did a lot of work in the tune of the headers and collectors. Moving the cats just sort of fine tunes the system. With my A4 and 2:73s and on the autocross ckt, I normally run the entire course if first gear and virtually never have to shift. Sometimes I am forced on the larger ckts with longer straights.