FAOSC with no cats?

[Ranger Coyote]

I found a document from ford that said the faosc doesn't even come into the equation until you are 16% off stoich.

1. Since I have no cats on my car does the FAOSC even work?
2. Should it be disabled with no cats?
3. Does it matter either way since my fuel trims are nowhere near 16% off?

[murfie]

"The rear oxygen sensor, located after the catalyst, is used for fuel trim corrections on some OBD-II vehicles. By virtue of its location, the rear sensor is generally protected from high temperatures and much of the contamination that affects the front oxygen sensors. In addition, the rear sensor sees exhaust gases that are equilibrated – they have already been converted by the catalyst so that there is very little residual oxygen. This allows the rear sensor to respond to much smaller changes in exhaust gas oxygen content. In turn, it then possible for the rear sensor voltage to remain near the 0.45 volt switchpoint. This characteristic allows the rear sensor to be used for fuel control. Under steady rpm and load conditions, the short term fuel trim bias can be adjusted so that the rear sensor voltage is maintained near the 0.45 volt switchpoint. This ensures that the catalyst is getting a stoichiometric exhaust gas mixture, despite any shift in the front sensor switchpoint. The rear fuel trim corrections are learned in KAM. Internally, this system is known as Fore Aft Oxygen Sensor Control (FAOSC). Note that FAOSC learns and reacts very slowly because the catalyst, with its large/slow oxygen storage and release characteristic, is part of the control loop. Also, this system cannot be used with a "y-pipe" exhaust where a single rear sensor would try to adjust dual front sensors."

1. since you have no cats FAOSC will no longer work correctly.
2. with no cats it should be disabled
3. I would say with out cats the FAOSC could actually slowly introduce unintended error instead of correction.

[txcharlie]

Isn't one of the functions of the rear O2s, to calibrate the WBs on the '11 and newer Coyote platform?