open loop is where you can really adjust the afc to control the air fuel mixture.
think of it this way:
closed loop : it's closed to tuning.
open loop: it's open to tuning.
in closed loop the ecu takes the o2 readings and tries to keep the mixture at stoich.
in open look the edu takes pre made maps from mazda and applies them taking into consideration MAF readings.
The AFC controls the MAF readings by either sending a higher or lower signal to the ecu, making it think that it's getting more (higher signal) or less (lower signal) air.
ecu sees less air = less fuel.
ecu sees more air= more fuel.
in closed loop this doesn't work because the ecu is taking the O2 sensor readings, soo lean = more fuel rich = less fuel.
in closed loop you can slightly adjust the settings but usually within a few runs the ecu learns around it. (short term / long term fuel banks)
the O2 clamp (output B ) clamps the o2 signal making the ecu see a lean condition which forces it into openloop where it takes the reading off the maf which you're controlling via the ssafc.
hope that helps.
