Flex Fuel Engines O2 sensors

[turbo_bu]

Stupid question for the day.... Was wondering what O2's that the flex fuel engines are running. Simple heated narrow band O2's? If so, then when they start to run on say E85, doesn't the switch point need to change since the air-fuel ratio changes? On gas it's 14.7:1 for E85 it's much richer (can't remember the exact number right now).

Otherwise, maybe on those engines it is running a form of wideband O2????

Thoughts here are aimed at trying to understand if when running on ethanol, if the fuel calculations are going into a form of open loop since the O2's would not be providing feedback (assumption is narrow band O2's).

[gmh308]

Stupid question for the day.... Was wondering what O2's that the flex fuel engines are running. Simple heated narrow band O2's? If so, then when they start to run on say E85, doesn't the switch point need to change since the air-fuel ratio changes? On gas it's 14.7:1 for E85 it's much richer (can't remember the exact number right now).

Otherwise, maybe on those engines it is running a form of wideband O2????

Thoughts here are aimed at trying to understand if when running on ethanol, if the fuel calculations are going into a form of open loop since the O2's would not be providing feedback (assumption is narrow band O2's).

Not a stupid question at all. :) They run the same NB O2's. O2's measure lambda and not air fuel ratio. And lambda needs to be 1 whether it is E0, E85 or methanol for example. So at lambda = 1 for gas the AFR will be 14.7:1, and E85 about 9.8:1. The output of the sensor looks the same. This is how the virtual fuel sensing works, basically seeing the sensor off centre after a fill and then working to trim it back, once the ECM reaches centre again it knows the % of ethanol as it knows how far it has trimmed to compensate from baseline gasoline.