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A word about "closed loop" fuel control.
The narrow band is just that.
High voltage .800mv means the exhaust gas has less oxygen than atmospheric.

Let's backup a few notch's
The O2 needs to warm up to somewhere ~650F before it starts to switch.
Most of the late model cars has heater's to speed the output up a hair.

As a side point ..a 32-36 or a 38 DGAS can switch a narrow band.

Yikes back to fuel control..
When the 02 is seeing .8mv the pcm/ecm will subtract a percentage of fuel to hit the target.
Of course it goes the other way around .
Say the 02 is reporting a reading of .2mv
The oxygen content is high
So guess what ...the puter commands more fuel.
Easy stuff :)
 

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Now lets get into self tuning.
First you'll need a good idea of the needed fuel across the map.
Then work up a base chart.
I love charts :)
Ok the PCM/ECM needs to hit the target right?

So it subtracts or adds fuel...this is done with long term fuel trims.
Also known as "adaptive fuel control" -self learning.
 

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The minimum amount of air flow will also need to be taken into account.
Well yes a nice idle is needed right?

A hint ...spark advance helps when a long duration cam is used.
The vacuum is low at idle there by making the bypass valve almost useless.
As everyone knows if you increase spark timing at idle the vacuum will also magical increase.
 
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