wideband 02 in closed loop

[kostelacd69]

the problem is when your runing the pe mode nothing is monitering what is happening with the motor. its just going off what ever the ve table says. so for any change in the envirorment the compurter is to stupid in a sence to adjust anything. well if the software would let you adjust the o2 volts from 0-1.5v to 0-5 volts, then you sould run closed loop and it would make happen what ever you are comanding. for instence if it went lean it would at least try to change it. just like stft but all the time. i such at spelling sorry.

[joecar]

You can have PE in closed loop.

[joecar]

So, how would you make this work...?

In CL the PCM commands some amount of fuel and then waits for the O2 voltage to move... then when it sees that, it commands the "opposite" amount of fuel and expects to see the O2 voltage change direction... i.e. the O2 voltage oscillates around some middle value... this happens when using LTFT's or STFT's or both.

With some widebands (e.g. LC-1) you can program the V:AFR function to be steep and narrow across stoich and to limit at 1.1V... when programmed like this, the wideband can produce a signal that the PCM likes and the PCM then trims to stoich...

Are you saying to choose another voltage switch point in the PCM and program the wideband around that voltage (i.e. steep/narrow function centered on that voltage)...?

[joecar]

The switch points vary by calculated airflow, see tables B4107, B4105.

[kostelacd69]

ok so im not familiar with b4107 not sure what that table does, but the other table just changes swithching voltage for the narrow band. which doesnt help what im trying to do. i need a table for the wideband from 0 to 5 v so that the pcm can read that low of af's. the narrow band is based around stoich and anything other than that it stops reading up to say 12.8 to 1 or so and the computer stops useing info after it comes out of stoich, where ever that maybe according to b4105. the problem is that the program doesnt have a area to put any voltages for a wideband, and doesnt read past stoich.

[joecar]

The OEM controller's algorithm is designed to make the NBO2 voltage switch up and down several times per second: the PCM drives the AFR to slightly above stoich, the NBO2 voltage responds by jumping to above 600mV, the PCM sees this and then drives the AFR to slightly below stoich, the NBO2 voltage responds by falling to below 300mV... this repeats as long as the PCM maintains Closed Loop...

driving the AFR just slightly above or below stoich causes the NBO2 voltage to jump up or down by 300-500mV... the transfer function is very steep and narrow.

The wideband would have to function in similar manner... this means you can pick only one switch point, regardless of how many are provided by B4107/B4105.

The OEM controller is not designed to just read the AFR from a wideband like some other engine controllers do.

(B4105 is referenced by "CL Mode" which comes from B4107 as airflow varies... there are many combinations of CL Mode and switching voltage based on airflow... so apparently the switching point varies as airflow changes.)

[kostelacd69]

right so like i was trying to say is the pcm only uses the nb for one area. how do i get it to read all areas from a wideband. i just simply may not be able to, but is there some one who makes software that will let me use a wideband and control and monitor it all???? thanks

[Highlander]

I don't see this as a feasible way to do this. As said before, the PCM commands an overshoot of "AFR" in the means of voltage. That means that if you target a 12.5 AFR mixture, you can oscillate between 13.3 and 11.7. Will the engine run as good in this way? I don't think so. That is why the GM ECU does not use WB on their stock form.

If there is a way to really control the overshoot (i've tried and the results vary too much) this could be possible. Still I wouldn't run it.

[ChucksZ06]

The aftermarket units from holley, fast, and others do what you want. They are much easier to tune than the gm also. Downside is the money they cost and may not be compatible with our crank triggers.