Hit 12.5 A/F on the dyno but o2's read 820 on the street. Normal?
 

Just curious guys cause I thought we wanted to be around 880 - 900 millivolts at WOT with our narrowband o2's to get a good a/f. I'm not getting any knock retard but am curious cause the last thing I need is another toasted motor.

I hit 12.5 a/f on the dyno (mustang dyno so it has load too), Now on the street I hit around 820 millivolts at WOT. Can you guys tell me what you think about this? I'm gonna hit the dyno again tomorrow and see what happens.

On my car 12.8=870mV, but that 50mV is as likely a
temperature difference as an air/fuel difference. Too
much variability in plumbing thermals when you get
away from the stock logs, to say what means what
on a modified setup.

If you could log in-car O2s at the dyno then you
could develop your own "mapping" of in-car to
wideband; semi-handy to know.

True enough, I'll keep that in mind at the dyno.