o2 question

[rickykline]

Which o2 is the pcm referencing for changes in fueling? The one on the Manifold or the one on the downpipe? the local parts store does not have the three wire o2 that goes on my manifold listed in there system
In my loggs the o2 readings are so inconsistant you can't get an idea of the afr at all.. wideband will say 14.6-15.2 cruising but the narrowband reading on my dhp will be undefinable it only touches 450mV maybe once the rest of the time it goes nutts, lean and rich and my trims are not bad either.. im stumped i figured my trims would be trashed if the o2 readings where inconsistant.

If requested i can try to post a .csv of what im talking about after work. I understand there should be some ocsilation in NB o2 readings but DAMN!

engine and mods listed in sig
Thanks,

[pocket-rocket]

The upstream (in the exhaust manifold) is the one that the engine bases fueling on.

[3400-95-Modified]

Ricky what are you trying to do? The narrow band will bounce from low mV to 800mV or so while driving... this is around stoich and is how the engine normally runs. You will see around 14.3-15.0 or higher on a wide band since there will be some lean spikes or rich spikes even when just cruising around. You'll never get a solid steady number when out of WOT and it's not designed to be steady at that cruising condition.

The oscillation is perfectly normal and the ecu recognizes that and adjusts with the trims but as you've said the trims are good so then there is nothing to worry about. If you see your WB staying more steady in a 13 or 15 range than mid 14's then yes I would begin to worry that the NB o2 is not doing its job and could be skewing the trims to make them look good when they really aren't, but at the same time, don't only trust your WB since those can also read wrong.