O2mv converted to AF ratio
sensor / exhaust gas temp so no one formula
can work, unless you have the gas temp known.
Even on a single vehicle, thermal history makes
the relation look like a "smear" and is unreliable
from one pull to the next.
The first one shows that a .87 o2 voltage could be a 10.2:1 or 13.2:1 or 14.2:1, depending on the exhaust temp.
With that said, typically these cars run good around .88-.90 na, if you need to rough it in for now.
The second chart just compares rich vs lean in relation to power and fuel economy.






