WB O2 after cat

[Tem]

Local dyno tuner had a wideband O2 sensor at the end of the exhaust (inserted from the tailpipe), which obviously means after cat(s) in most cars. Does it really show something usable after the cats?

For example, it kept showing some 10-11AFR to stock 2ZZ-GE in Corolla and Celica, which seems a bit weird. I only realized it afterwards, so I couldn't ask the tuner about his thoughts on the matter, but what do you guys think about it?  s:? :? s:?

[markiii]

seems to work, as they decided Adams was running way to lean and needed remapping, based on having the 02 in that location.

However I caveat that he has no main Cat.

[Tem]

seems to work

That's the point...does it work, or does it just seem to work?  s:? :? s:?  Both 2ZZ's seemed to give sensible AFR values, which implied they are very rich under WOT, rich enough to keep them happy with boost. No one questioned it on the dyno, but I started to wonder about it afterwards...

The more I think of it, the more this makes sense:
 m http://www.innovatemotorsports.com/foru ... php?p=8577 m

[Slacey]

Thor have the equipment to monitor either from the exhaust post cat, or pre-cat via one of the existing O2 bungs. They plugged the WB in pre-cat for my tune as they said it was infinately more accurate there than post cat.

[Tem]

Did they say anything about how much difference there could be?

Anyone have access to two widebands?  s:twisted: :twisted: s:twisted:

[aaronjb]

Did they say anything about how much difference there could be?

Lots  s:lol: :lol: s:lol:

Did you see BenF's recent post with traces from the (stock, narrowband) O2 sensors both pre- and post-cat? You'll see (AFAIK) the same kind of difference with a wideband - the difference is that the traces won't just be highs and lows, it'll give you a proper A/F reading - but the pre-cat will cycle very rapidly, while the post-cat will cycle on a much longer timeframe of several seconds (between lean & rich, that is)

That's my understanding, anyhow..

[Tem]

You mean this one?
 m http://www.mr2roc.org/phpBB2/viewtopic. ... ght=#92548 m

It's kinda hard to read those graphs  s:? :? s:?  At least they seem to have the same form up/downstream and both use about the whole scale.

[Jap GT300]

ON the first occasion they measured with a wideband on the 3rd O2 location, but when I went back on Friday they shoved a rod up my pipes.

[Tem]

they shoved a rod up my pipes.

Isn't that a bit gay?  s:lol: :lol: s:lol:


So was there a difference in those measurements?