NBo2 switching problem

[Mark300]

Hi, Please could someone help me, i have been really struggling with this. My ecm is a E38 with 6.0L L98 motor, the car is an 08 Lumina SS. My LC1 WB in closed loop MAF reads on average 14.20 AFR, but my command AFR is 14.63. I have tried to adjust the switching point, and after every attempt i have reset fuel trims. Why does it not want to change. Am I doing something wrong. Mark

[gmh308]

Hi, Please could someone help me, i have been really struggling with this. My ecm is a E38 with 6.0L L98 motor, the car is an 08 Lumina SS. My LC1 WB in closed loop MAF reads on average 14.20 AFR, but my command AFR is 14.63. I have tried to adjust the switching point, and after every attempt i have reset fuel trims. Why does it not want to change. Am I doing something wrong. Mark

Is your LC1 set for regular gas? 14.6-14.7 or so? Maybe it needs a free air calibration.

Your NB's should be ok and reading lambda of 1.0 (on regular non ethanol fuel this would be about 14.6-14.7AFR). What are your long term and short term trims doing? LT's + or -? STFT's averaging zero?

[Mark300]

My LC1 is set to regular gas. Did my third free air test. My LT's are around +5% at idle, but steadly drops off to around 1% at 4000rpm, as it goes higher through the rev range. Can you change or calibrate the NBo2, to make sure that it is reading correctly vs the WB LC1. My concern is that the sensor can mess all the wonderful work done, because it is trying to learn towards a lamba that is not correct. My feeling is that once i know for sure this sensor is measuing correctly, then i can calibrate my Maf on ben LTFT

[ScarabEpic22]

Have you properly setup your VVE table? Also does the gas you have contain ethanol? If it does that will be why your actual AFR is richer than commanded.

[gmh308]

Have you properly setup your VVE table? Also does the gas you have contain ethanol? If it does that will be why your actual AFR is richer than commanded.


If the LC is setup for AFR it would read gas AFR regardless of fuel right?


My LC1 is set to regular gas. Did my third free air test. My LT's are around +5% at idle, but steadly drops off to around 1% at 4000rpm, as it goes higher through the rev range. Can you change or calibrate the NBo2, to make sure that it is reading correctly vs the WB LC1. My concern is that the sensor can mess all the wonderful work done, because it is trying to learn towards a lamba that is not correct. My feeling is that once i know for sure this sensor is measuing correctly, then i can calibrate my Maf on ben LTFT

Well I dont think anyone has managed to budge Gen IV O2's yet. We run Techedge O2 and generally they match right up with the stock NB's in closed loop.

Chuck COW on here had some interesting challenges with LC's, maybe worth checking his posts out.

[ScarabEpic22]

If the LC is setup for AFR it would read gas AFR regardless of fuel right?

Correct, unless you reprogram it in LogWorks for a different stoich point. Come to think of it, unless the ECM thinks its commanding stoich and its actually commanding 14.20 it might be a tune related thing. With LTFTs around 5% at idle that could be a partial factor.

To the OP, regarding your 1% LTFTs at 4000+rpms, what does your WB say? Get a log of it.


Well I dont think anyone has managed to budge Gen IV O2's yet. We run Techedge O2 and generally they match right up with the stock NB's in closed loop.

Chuck COW on here had some interesting challenges with LC's, maybe worth checking his posts out.

Interesting to note, I wonder if my LC1 is actually displaying the actual AFR, after hearing about some people's issues with them its made me a little nervous. When I get my truck on a dyno I guess Ill figure it out pretty quickly how my LC1 stacks up against the dyno wideband.

[swingtan]

FYI. O2 switch points have no effect in the E38, not yet anyway. It's been like this for a long time and I believe that there are a couple of calibrations yet to be defined.

Firstly, the CL airflow mode table does not exist at all. So you can;t fine tune the switch points to match air flow.

Secondly, I get the feeling that there is a variable switch point enable or possibly a hard min / max setting for the switch points.


As has been said, I'd be suspecting the LC1 is displaying the wrong data. Log the following, and see what the results are.


NB O2 Voltages: Do this for both banks. After a good run, choose a section of the log where map and RPM are stable and you are in CL. The average voltage should be fairly close to 450mV.
STFT: Again for both banks. This is really just to see what is going on. the trims should be fairly close when compared to each other and should be within +/- 5% ( though up to 10% is not too bad )
WB O2 reading: Average the value for the same section as above and see what the average is.


Make sure you look at the averages over as big a sample as possible. When in CL mode, you really need to watch the averages more than specific points. That way you avoid issues where you may focus on the rich swing of the NB O2 control and think you are running rich.

Post up a log or 2 if you get the chance.

Simon.

[Highlander]

That table exists in H p T.

[Highlander]

FYI. O2 switch points have no effect in the E38, not yet anyway. It's been like this for a long time and I believe that there are a couple of calibrations yet to be defined.

Firstly, the CL airflow mode table does not exist at all. So you can;t fine tune the switch points to match air flow.

Secondly, I get the feeling that there is a variable switch point enable or possibly a hard min / max setting for the switch points.


As has been said, I'd be suspecting the LC1 is displaying the wrong data. Log the following, and see what the results are.


NB O2 Voltages: Do this for both banks. After a good run, choose a section of the log where map and RPM are stable and you are in CL. The average voltage should be fairly close to 450mV.
STFT: Again for both banks. This is really just to see what is going on. the trims should be fairly close when compared to each other and should be within +/- 5% ( though up to 10% is not too bad )
WB O2 reading: Average the value for the same section as above and see what the average is.


Make sure you look at the averages over as big a sample as possible. When in CL mode, you really need to watch the averages more than specific points. That way you avoid issues where you may focus on the rich swing of the NB O2 control and think you are running rich.

Post up a log or 2 if you get the chance.

Simon.

not only that, be sure to disable post cat o2 testing.

[mr.prick]

Positive LTFTs tend to make AFR richer, that is why you don't want LTFTs during PE.

The LC-1 like all WBO2's convert AFR from Lambda and it will show 1L for stoich regardless of the fuel being used.
This is why you need to set the fuel type if you want to see AFR properly.
The conversion is Lambda*Stoich AFR

The LC-1 is know to mysteriously change the fuel setting to Custom
making you see an extremely odd AFR reading.
We can't define serial WBO2, that is set by the WBO2 brand and if you want to change the conversion you will need to make a calc_pid for the fuel type you are using referencing serial Lambda
Example for E10:
{EXT.WO2LAM1}*14.13
This will give you AFR for E10 regardless of what the LC-1 fuel setting is.
If you are using analog you can use this spreadsheet to define Lambda from volts. (http://forum.efilive.com/showpost.php?p=111408&postcount=4)

[Mark300]

Hi All,

Thank you for all the great reply's. I have been away for a few days and have only been back today. I tend to agree that the LC1 is most likely the problem. To my knowledge, our fuel has no ethanol. The cats have been disabled, as I have a complete performance exhaust from the block. I have also installed a 160F degree thermostat and done all the relevant ecm fan adjustments.
I am going to try swingtan's suggestion this week in looking at the average mv on the nbo2, as well as pop in to my local dyno shop and check it with a gas analyser.
The VVE tables have not been calibrated yet, I am running full MAF (from 400rpm). I am working through Weatherman’s calibration tutorial that he is in the process of writing.
This is where I noticed the problem. In his tutorial it is important to make sure that the nbo2 are reading 14.63 as this is the baseline to calibrating the whole system. If the nbo2 are not correct, then the rest will be out. So, I was checking my nbo2 with my wbo2 and notice the difference. Then tried to adjust the nbo2 (from 14.20 to 14.63) and could not. I don’t want to alter anything until I know that I can accurately read 14.63.
So, at this point what I can understand from all the responses regarding the nbo2, what they read is what you get. Unless they are faulty