wideband 02 in closed loop

[kostelacd69]

Is there any way to wire in a WB to the pcm, and have it control the af in closed loop. basicly how a NB does your stoic but all AF not just 14.68. If there is a way what is it or what do i buy. Thanks David

[swingtan]

Depending on the WB unit used, many have a NB simulator output as well. So you can hook that up to the normal NB plug and run normally in CL. The other option is to just get another O2 bung installed in the exhaust and run both the NB and WB sensors.

Simon

[kostelacd69]

yeah my wideband has an analog output. maybe i didnt explain it well enough. if you hook a wb to it, it will still only monitor stoich. I want it to monitor and adjust what ever af im comanding. Say the 11.50 af under wot, right now it will come out of semi closed loop and run dirrectly off of the boost VE table. i want the computer to adjust with a wideband in that area. The MEFI 4 stuff does it on like sand cars or hondata does it for hondas. i want it to never come out of closed loop and use the WB all the time to adjust all the time. Does that make more sence?

[ScarabEpic22]

Wont work, the PCM only sees right around 14.7. No way to log the actual AFR/EQ/Lambda with the PCM PID. No matter, EFILive lets you record it in the Scan tool or BBL too. Just wire your WB output to the analog input of your FlashScan and select the appriproate PID in the Scan tool.

[kostelacd69]

yeah ive already auto ve it and tuned with the wb. just wasnt sure if some one sold a different pcm that may be able to hook up and read a wideband, or somthing to get it to run the wb all the time. the reason is that i live at 4500 ft with 7000 da on average, but im always going to sea level or 100 ft or so and im tired of haveing to retune for diff elavations. the sand cars that we build has a wideband wired in, so no matter where you go or what the weather is, as long as the ve tables are close you dont have to worrie about it. it adjusts itself.

[ScarabEpic22]

yeah ive already auto ve it and tuned with the wb. just wasnt sure if some one sold a different pcm that may be able to hook up and read a wideband, or somthing to get it to run the wb all the time. the reason is that i live at 4500 ft with 7000 da on average, but im always going to sea level or 100 ft or so and im tired of haveing to retune for diff elavations. the sand cars that we build has a wideband wired in, so no matter where you go or what the weather is, as long as the ve tables are close you dont have to worrie about it. it adjusts itself.

I see, all the VW/Audi Bosch ECMs use a WBO2 input but the likelihood of getting one to work with a GM is slim to none.

I see, 4500ft to sea level will cause a big change.

What year and PCM are you using? If its an LS1 pre 1MB then Id recommend using a COS and B3647 for open loop fueling. There's probably a way to wire up the nitrous input that modifies the VE table values by the factor in table A0015 (COS5) in such a way you could bypass having to retune. It wouldnt be perfect, but it would probably get you close enough that the LTFTs and STFTs would get you close.

[kostelacd69]

the pcm is 2001 which ever one that maybe. i figured you couldnt do it but i thought id ask. thanks anyway

[ScarabEpic22]

the pcm is 2001 which ever one that maybe. i figured you couldnt do it but i thought id ask. thanks anyway

Look into running a COS, there has to be a way to do it with one of the COSs EFILive offers. Its free to upgrade and use, just have to upgrade your PCM to the base 2002 Camaro OS then go to the COS.

[swingtan]

Actually, there may be a way to run CL all the time, but you would need to make use of the O2 switch point tables a lot more. We know that the NB output voltage is too erratic to accurately control fueling, but the WB signal would be much more accurate. So I think you could try something like this...


Take your WB of choice and note the voltage range from the analogue O/P. The O2 switch point tables for the LS1 only range between 0-1.1V and most WB units will give 0-5V, so you would need to set up a voltage divider to drop the maximum voltage to something in the range that is needed.
Using the WB details, work out the Voltage vs AFR table so you know what voltage = what AFR. Then, correct the voltage values for the voltage divider used in step 1 to give the 0-1.1V equivalent AFR's.
Using B4105 and B4107, set up the required O2 swtch points to give the desired AFR's. You will need to work out what the CL Mode air flow values are for different engine loads, but it "should" work.
You may then need to disable PE mode so the PCM stays in CL. When the airflow changes for differing CL Modes, the O2 switch points should adjust to give a richer or leaner mixture, depending on the airflow. Obviously, more airflow = more load, so you would want a richer mixture.


I have no idea what this would run like though. I guess there could be certain engine conditions where the mixtures will not be ideal, as you could have hi RPM, low load air flow conditions that want a "leaner" mixture, but low RPM, higher load conditions that want a richer mixture and both conditions may have similar air flow. It's an interesting thought for sure and may be a good way to run a CL cruise, adjusting mixtures for changes in load before going into PE ( hence the may in step 4 above ).

I'd give this a try in my car, but the E38 switch point tables have never worked so I can't try it. I actually like the idea of a "variable CL lean cruise" mode.

Simon.

[mr.prick]

What's wrong with using fuel trims & PE?
It's the best we have with GM PCMs.

You can use the RR w/WBO2 in OL for near perfect fueling via
VE and/or MAF but it's not worth the trouble for DD. IMO

[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.