Post-Cat wideband placement good enough?

[FstBlkZ28]

I know that having the wideband sensor pre-cats is considered ideal. But with my exhaust setup now, I have no room to throw an extra bung in before my cats. So I'm wondering if putting the sensor post-cat would allow me to get a good enough autotune so I can run OLSD .. then move the sensor to the original sensor location and fine tune as necessary. Will this work?

[joecar]

This will work only if you have no cats.

[kbracing96]

I ran a post cat WB for quite a while with because of my turbo location. I had no problems with it. I've seen a couple of test with pre and post cat WB test and there is not more then a tenth of two difference either way. I think there is not enough different for it to affect the tuning.

I have never seen any proof that cats will effect WB reading.

[joecar]

Okay then adjust the calc pid to account for two tenths.

Edit: I thought the cats would "smooth" out the O2 content.

:nixweiss:

[FstBlkZ28]

Ok great! Thanks guys ... I'm just ready to get the wideband on there so I can start doing some real tuning and get the OLSD thing started. 2 tenths will get me close enough to get it running good enough without the o2's in OL, then I'll throw the wideband in the stock o2 sensor location and fine tune if needed.

[Bruce Melton]

Ok great! Thanks guys ... I'm just ready to get the wideband on there so I can start doing some real tuning and get the OLSD thing started. 2 tenths will get me close enough to get it running good enough without the o2's in OL, then I'll throw the wideband in the stock o2 sensor location and fine tune if needed.

I ran both a tailpipe after cat and my in header PLX tied to FS and was amazed the AFR difference was not noticable from Dynojet scan during dyno runs.

[ringram]

Ive seen 0.5:1 difference from LC1 and tailpipe. Apparently others have seen similar too.
O2 is used up in the cat, so there will be differernces.
2C + o2 = c02 etc.

[FstBlkZ28]

Ive seen 0.5:1 difference from LC1 and tailpipe. Apparently others have seen similar too.
O2 is used up in the cat, so there will be differernces.
2C + o2 = c02 etc.

Ok, so if its .5 off ... is that "close" enough for an idle/part throttle tune? Just so I can get the car running OLSD?

[kbracing96]

Yes, I ran and tuned my truck w/turbo for almost a year using the WB after the cats and turbo. Just recently put a off road y-pipe on it.

[joecar]

Yes, I ran and tuned my truck w/turbo for almost a year using the WB after the cats and turbo. Just recently put a off road y-pipe on it. With your ORY, did the BEN's change very much...?

[kbracing96]

With your ORY, did the BEN's change very much...?
Very little, most cells where +/- 1-2%. Who to say whether it was the cats or the increase in exhaust flow from the less restriction.:nixweiss:

But I would still say the cats have minimal affect on the WB reading

Who is to say that the WB is even that accurate in the first place. Isn't it more of a tool to lets us know how much of a change we made? Is the reading it gives 100% accurate? I don't use these tools as persists instruments, I just use them as points of reference to accomplish a goal of making the most power and the best economy without destroying anything.

[joecar]

Very little, most cells where +/- 1-2%. Who to say whether it was the cats or the increase in exhaust flow from the less restriction.:nixweiss:

But I would still say the cats have minimal affect on the WB reading
Your +/-0.01-0.02 BEN's have proven this.