02 Switching points

[DaddySS]

The 02 switching points on the OSs are different - 02 vs 99 to 02 conversion vs 2000 (my original). I know the 00 and 02 have the same part number 02 sensors so how much difference does it make which you use and is there a recommendation? What effect will it have on LTFTs?

[BlackGMC]

The O2 switch points are basically the voltage the computer will switch around while in Closed Loop. So if you want a leaner or richer AFR then adjust your switch points accordingly. I have mine set to switch around ~15.2-15.5 while in a light load, which in my case is ~ 250mV. It is good for a couple more MPG.

[DaddySS]

Thanks, so question: lower voltage will result in leaner mixture via the LTFTs and higher voltage will do the opposite? What are the calibrations on the x axis - it just says CL mode 0, 8, 16, etc.?

[dc_justin]

CL Mode is defined in the table beneath the O2 switch points, closed loop mode. You can correlate a CL Mode to an amount of airflow via that table.

Justin

[Chevy366]

The O2 switch points are basically the voltage the computer will switch around while in Closed Loop. So if you want a leaner or richer AFR then adjust your switch points accordingly. I have mine set to switch around ~15.2-15.5 while in a light load, which in my case is ~ 250mV. It is good for a couple more MPG.
So does this affect injector pulse width ?
Does changing values make PCM see the injectors as larger or smaller , although they are not , because of pulse width change ?
This is not used to adjust the injector swing , injectors swing from 14.7 to 15.1 to maintain Stioch , by making the swing closer say from 14.7 to 14.8 instead of 14.7 to 15.1 ?

[dc_justin]

So does this affect injector pulse width ?
Indirectly


Does changing values make PCM see the injectors as larger or smaller , although they are not , because of pulse width change ?
No relation to injectors


This is not used to adjust the injector swing , injectors swing from 14.7 to 15.1 to maintain Stioch , by making the swing closer say from 14.7 to 14.8 instead of 14.7 to 15.1 ?
Yes it does. It adjusts the point that the PCM switches from rich to lean, and thus the timing of the STFT adjustments.

[BlackGMC]

So does this affect injector pulse width ?
Does changing values make PCM see the injectors as larger or smaller , although they are not , because of pulse width change ?
This is not used to adjust the injector swing , injectors swing from 14.7 to 15.1 to maintain Stioch , by making the swing closer say from 14.7 to 14.8 instead of 14.7 to 15.1 ?

Not a clue on injector pulse width, perhaps Justin can answer that one... From what I have observed and been told. The computer adds and substracts fuel around the O2 switch point, via Fuel Trims. For example if you have it setup for 450mV (~14.7), the computer will add and substract fuel to hover/flucuate around 450mv. So if you have them set lower or higher the PCM will do the same for a lower or higher AFR. Another example: I have mine set to 250mV which is ~ 15.2- 15.5 (established by alot of logging), My wideband reading is usually swinging back and forth between 15.0 and 15.5 in the lower load settings. I have gotten about 1-2 MPG out of it. I orginally had them set to 300mv which made the AFR 14.7-15.2. I might try 225mv next time I update my tune.

[Chevy366]

Indirectly

No relation to injectors

Yes it does. It adjusts the point that the PCM switches from rich to lean, and thus the timing of the STFT adjustments.
So why in 04 or 05 did GM go to straight 450mv as other OSs before that had varying O2 mv ?
So the STFT are used to establish the LTFT table and are reset every so often how does this help then ?

[dc_justin]

So why in 04 or 05 did GM go to straight 450mv as other OSs before that had varying O2 mv ?
So the STFT are used to establish the LTFT table and are reset every so often how does this help then ?

STFTs are constantly changing, they are what drive the O2 switching activity.

[MoTruck]

If I understand some earlier posts, the LTFT's are added to the PE fueling, if they are positive. Wouldn't lowering your switch points also lower the LTFT for that same range? Does this affect the calculation used for the PE mode, since the LTFT's would have negatives in the lower ranges? Thanks.

[DaddySS]

So back to my question, will the 02 switching points being higher in effect result in a richer mixture during CL mode since the LTFTs will add more fuel to your base VE calculations?

[5.7ute]

I would say the overall average fuel mixture would be richer due to the higher voltage switch point.
Has anyone compared switch point in the OS to O2 sensor position in the exhaust? This to me would be the reason for a change in the different OS, since a change in exhaust gas temp will change the voltage output of a narrowband sensor. Albeit slight due to the sensors internal heater.

[DaddySS]

The sensor positions are the same. A few of the major differences between the pre and post 01 cars is EGR (98 to 2000), the intake manifold and the cam. I suppose my question is really this - there is a 50- 100mv difference in various cells - how much difference might that make, and should I be concerned about which value to use?

[BlackGMC]

The sensor positions are the same. A few of the major differences between the pre and post 01 cars is EGR (98 to 2000), the intake manifold and the cam. I suppose my question is really this - there is a 50- 100mv difference in various cells - how much difference might that make, and should I be concerned about which value to use?

50-100mv really won't make a difference. I lowered mine from 450 down to 250 and it only moved the AFR from 14.7 to 15.2-15.5

[Chevy366]

Since the part numbers are the same I would think not much at all , that would be my only concern is if the O2s were different man .
Just looking to keep the swing near Stoich .