Kooks Long Tube Headers

[Zig]

As long as the rear O2's are installed and not throwing a code, the PCM will presume the system is operating normally .

I think people are confused as to what FAOSC does, The PCM monitors the rear O2 and all it's looking for is XX amount of oxygen post cat's.

If the PCM see's too much or too little O2 , it'll adjust the lambda to bring it in tolerance.

And if it can't it'll throw P2096/P2097 or P0420/P0430 code.




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Would that indicate distance between the two is paramount?

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[Junkyard Dog]

I do not know anything about this, how it works, nothing. I am just posting what I find, which seems to indicate that the downstream sensors do play a role in air/fuel ratio.

Upstream Sensor:

The upstream O2S sensor is located in the exhaust downpipe before the catalytic convertor. It provides an input voltage to the PCM. The input tells the PCM the oxygen content of the exhaust gas. The PCM uses this information to fine tune fuel delivery to maintain the correct oxygen content at the downstream oxygen sensor. The PCM will change the air/fuel ratio until the upstream sensor inputs a voltage that the PCM has determined will make the downstream sensor output (oxygen content) correct. The upstream oxygen sensor also provides an input to determine catalyst efficiency.


Downstream Sensor:

The downstream heated oxygen sensor is located near the outlet end of the catalytic convertor. The downstream sensor is also used to determine the correct air fuel ratio. As the oxygen content changes at the downstream the PCM calculates how much air fuel ratio change is required. The PCM then looks at the upstream oxygen sensor voltage and changes fuel delivery until the upstream sensor voltage changes enough to correct the downstream sensor voltage (oxygen content). The downstream oxygen sensor also provides an input to determine catalyst efficiency.

https://naxja.org/threads/downstrea...t=14.7 to 1 Air Fuel,shorted or open circuits

 

[Junkyard Dog]

All of these sites say the lack of a downstream sensor will mean that the engine mixture will be "rich," the safe mode.

 

[Junkyard Dog]

From the previous version of this web site (generation 6) in response to everybody saying they are not important:

"According to a good friend who is also a big name tuner says they're actually important. Over time he said that the car will use the rear o2 to help recalibrate the front o2 sensors as a wideband."

https://www.mustang6g.com/forums/threads/back-o2-sensors-how-important-are-they.40393/

This response seems to line up with what American Muscle says.

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