O2 Switch Point Adjustment

[swingtan]

Hi All,

I've playing around with the switch points for the O2 sensors in the E38 ECU. B1515 and B1516 allow the setting of the O2 switch voltage to be adjusted depending on the "Airflow Mode". This seems fairly self explanatory, but there are no tables in the OS that describe the "Airflow Mode" or allow any changes to it. In the LS1 settings, there is a table that sets the "CL Mode" depending on the measured air gm/S, but there is nothing like this in the E38.

I'm currently running an ethanol blend fuel and would like to try tweaking the switch points a little depending on engine load, but 2 things are stopping me ATM.

1. I have no idea what the "Airflow Modes" relate to.
2. the settings in B1515 and B1516 don't seem to make a lot of difference anyway. I've tried varying them from 450mV down to 170mV and the averaged measured O2 voltage remains at 470mV

I've even looked at trying to go OL and use B0148 to make a pseudo "lean cruise" setting, but again, this has no effect on measured AFR. Has anyone got either of these working as expected, or is there more calibrations that we need before these will effect the final AFR?

Simon

[The Alchemist]

I have also wondered about this and have found little or no change to AFR when changing switch points, unlike the Ls1 system...
Mike

[ringram]

Yep nothing here either.

Going full open loop and scaling the VE table as per MacGuyver resulted in the O2 readings being nice and low. But of course you cant tune easily to that.

[mr.prick]

i tried once before, with BEN factor and saw no changes.
maybe another technique is need, like a calc pid from LTFTs?

[oztracktuning]

Changing the shift point will work. You just have to go much more extreme because the ECM is much quicker at switching than the older ones.

Its interesting that the more recent VE Commodores all seem to be in closed loop at closer to 15.0:1 anyway

[swingtan]

Changing the shift point will work. You just have to go much more extreme because the ECM is much quicker at switching than the older ones.

Its interesting that the more recent VE Commodores all seem to be in closed loop at closer to 15.0:1 anyway

So further than 170mV? I would have thought that Id have seen some sort of change by that point. I'd been progressively dropping the switch point down from 450mV and then checking the average CL AFR's. From 450mV down to 170mV I haven't seen any change in average at all, it's remaining at 14.75:1(min 14.12, max 15.45).

We still need some help[ with the "Airflow Modes" as well. Sure you can just set the switch point as a flat line and not care, but it would be nice to be able to adjust the CL AFR for slight load changes. At the moment, we have no idea if the figures for the Airflow Mode are the same as for the LS1 or if they use a table with different settings.

Simon.

[hymey]

My car is Jan 08 build and in closed loop it sits up around the 14.9:1 mark.

[ringram]

Whats your switchpoints hymey?

[swingtan]

I must be missing something as I've tried adjusting the switch points down to 100mV and still see no change in the measured AFR's or the average O2 voltage when logged. Average voltage for both O2's remains at around 430mV when measured through the V2. I've stuck this on the back burner for now while look at some other things.....

Simon

[hymey]

Whats your switchpoints hymey?

They are stock(450), I haven't touched them, weather or not the 02 sensors are stuffed I don't know.

I thought it was my w/b out but in my mates VE it reads 14.6- 14.7 its an 06 model.

When I forced mine open loop to go leaner I didn't get that much different economy. Keeping the afrs above 14.0:1 on the open road helps a lot. For example, I set my mates Maloo to drop into PE at 6% TP(30% really) and 15kpa. And commanded 14.0:1 upto 3000 rpm as he was towing a trailer on open trips a lot...So in cruise control when it needed more torque for hills, etc the car wouldn't dump in a lot of fuel when going out of closed loop...ie 14.7 to 13.0:1...By setting it up so it would only go to 14.0:1 on hills, it increased the engines torque enough to do the work without using excessive fuel. It dropped consumption by 3.0L/100km by doing this. So going leaner in a very heavy VE doesn't necessarily mean you get much better economy like the earlier models but controlling it more in these situations I found helped a lot.

I to tryed changing the switch points with very low numbers and it didn't work...What is the lowest setting Simon???? Have you tried dropping it to the lowest setting just to see what happens.....

Joel