accuracy of the stock o2 sensors above stoich???

[swingtan]

yes. In this case though, you would have the tune in CL mode and use the STFT's to gauge the current state.

[mistermike]

There is a legendary fellow on LS1GTO who shall remain nameless. He steadfastly insists that WOT tuning can be safely accomplished with a NB sensor, and that all of our insistance that he use a WB is merely a cruel plot to relieve him of his money. He's on his third motor, not that I'm implying any correlation here.

[joecar]

Consider how the closed loop algorithm works: the PCM drives the AFR in one direction (crossing the "switch point") and looks for the NBO2 voltage to go in that direction by a sufficient amount; then when the PCM sees that swing it drives the AFR back in the opposite direction (crossing the "switch point") and again looks for the NBO2 voltage to swing back in that direction... this is then repeated as long as the PCM stays in CL mode...

the NBO2 voltage:AFR relation is approximately linear for about 100mV on either side of the switch point and then rapidly ramps up/down until it bangs the "pegs"...

the only way to accurately know wheather the AFR is stoichiometric is to perform the closed loop algorithm... if the voltage can be made to cycle then the AFR is very close to stoich... if the voltage pegs up or down, then the AFR is not stoich... i.e. either yes or no with no in-betweens...

this tells me the NBO2 sensor might be accurate (and this may even be questionable) only at the switch point (typically 450mV) and inaccurate elsewhere.


$0.02.