I don't know what bike,, model, year, etc you have. Putting that on your profile will help future enquiries. This is the situation on EFI Bonnevilles for what it's worth:

The ECU only seeks information from the O2 sensors at below 6% throttle and when the AFR 14.5:1 is shown on the AFR tune map. These are basic, narrow-band sensors, present only to keep emissions low enough to pass homologation tests. They don't make the engine run any better. Not to be confused with the far more efficient and sophisticated wide-band sensors used on cars.

If the AFR settings on modified tune maps is set below 14.5 the ECU no longer looks for this info from the sensors.

Adjustments for atmospheric pressure, temperature, air density, etc are taken care of by other sensors like
the Barometric pressure sensor (scroll to post 12 on that thread, I've just added some more info that I couldn't fit in the original post ):

http://www.triumphrat.net/twins-technical-talk/160380-efi-bonneville-barometric-pressure-sensor.html

The temperature sensors:

http://www.triumphrat.net/twins-tec...ns-technical-talk/160782-intake-and-oil-temperature-sensors-on-efi-bonnies.html

And the MAP (Manifold absolute pressure) sensors:

http://www.triumphrat.net/twins-technical-talk/149354-map-sensors-on-efi-bonneville-long-post.html

 

...The ECU only seeks information from the O2 sensors at below 6% throttle and when the AFR 14.5:1 is shown on the AFR tune map. ....

And also only when fully warmed up (> 85C) - is open loop during warm-up phase.

.... The ECU will use the other sensors to fine tune the mix at different riding conditions ....

The ECU use look-up tables stored in memory to determine how much fuel to deliver based on throttle position (or MAP sensor) and Engine RPM - then it modifies the derived table value by curves according to Engine Temperature, Air Temperature and Atmospheric Pressure.
Although the system does not operate in closed loop out-with the boundaries indicated by Forchetto, the ECM 'adapts' (learns) with a long-term trim that is constantly updated while the system is in closed loop.
i.e. if the ECM finds that it spends more time trying to make the Fuel Less Rich over a period of time, then it will create a trim based on that accumulation of knowledge to first apply that trim, as opposed to starting purely from the table values each time bike is started, That long term trim is constantly evolving all the time it actually is in closed loop.
So that Trim will also apply even when outside of closed loop.
Closed loop is a real-time trim that is applied almost instantly to achieve the Lamda value as measured by the O2 sensor.
Of course if O2 is disabled, it can never learn those long term trims - so when changing from for instance Ethanol Fuel Winter Blend to Summer Blend, the system has no way to adapt for that - only from the constants to which it can react

 

I don't have bike yet but I'm saving money to get a new thunderbird storm

Ok, if I understood it, The ECU will use the other sensors to fine tune the mix
at different riding conditions.

Also, with the o2 sensors disabled, the bike will rely on the programmed map at any throttle position as an open-loop system. right?

Gracias amigo

 

Also, with the o2 sensors disabled, the bike will rely on the programmed map at any throttle position as an open-loop system. right?

Gracias amigo

Yes, that's it.

 

So, a bike with a PCV+AT and its WBo2 sensors, has its ECU permanently working in a closed-loop mode? otherwise I can't see the benefit of the AT.