Afr adjustment problems E38 L98

[Mark300]

Hi All,

Over the last view weeks/months I have been working with weatherman Shaun’s concepts on MAF and VE calibration and have been having some good success. However I made a change yesterday and i got some unusual results. I changed my AFR from 14.63 to 14.00 (table B3671) and the results were unusual. On my scanner the command fuel is showing 14:00, but my LC-1 shows no change from before. However my LTFT change by up to 5% from what they were.

How is this possible. I am working in AFR and not EQ, could this be a factor

regards

Mark

[odd boy]

Post the tune

[mr.prick]

Are you using serial or analog connection?
If you are using serial you will need to change the fuel setting with the Logworks software to match {B3601}
http://forum.efilive.com/showpost.ph...0&postcount=11

For analog you will need to match the output range with a new calc_pid expression.

There have been countless posts on this the past 2 days.

[Mark300]

Hi All,

I will follow up on those points.
The issue that is confusing me though, is why did the LTFT move by the same % I change the AFR in table (B3671). When I set table B3671 to 14.63 my LTFT are averaging +/- 0.5% across the MAF Hz range. Which is good, but when I change my AFR from 14.63 to 14.00 which is around -5%. My LTFT went from an average of -0.5% to -5% across the Hz range on the MAF.
So what I am trying say is that even though I change the AFR, the LTFT are moving me back to 14.63. why is this happening. I even tried changing table B0141-open loop normal command fuel in gear, but I keep getting 14.63 on my LC1. I believe the LC-1 is correct as it is support by the fact that the LTFT are adjusting by the -5% to bring me back to 14.63. why does the car not go to the set AFR in table (B3671). The command fuel pid is showing 14.00 in the scanner

Regards

Mark

[gmh308]

Hi All,

I will follow up on those points.
The issue that is confusing me though, is why did the LTFT move by the same % I change the AFR in table (B3671). When I set table B3671 to 14.63 my LTFT are averaging +/- 0.5% across the MAF Hz range. Which is good, but when I change my AFR from 14.63 to 14.00 which is around -5%. My LTFT went from an average of -0.5% to -5% across the Hz range on the MAF.
So what I am trying say is that even though I change the AFR, the LTFT are moving me back to 14.63. why is this happening. I even tried changing table B0141-open loop normal command fuel in gear, but I keep getting 14.63 on my LC1. I believe the LC-1 is correct as it is support by the fact that the LTFT are adjusting by the -5% to bring me back to 14.63. why does the car not go to the set AFR in table (B3671). The command fuel pid is showing 14.00 in the scanner

Regards

Mark

Assuming you are running closed loop then the O2/LTFT system will always trim to whatever stoich needs to be for the fuel you are running....which must require around 14.63:1 AFR for your fuel. Change the fuel to 14:1 simply means that your O2/LTFT relationship says it is incorrect and will trim 5 rich to meet the stoich objective.

Open loop is a different matter.

[Mark300]

Hi Gmh,

Thank you for your reply. So in a nutshell, what you are saying is that I can't change my AFR from 14.63 in closed loop.

[gmh308]

Hi Gmh,

Thank you for your reply. So in a nutshell, what you are saying is that I can't change my AFR from 14.63 in closed loop.

Thats correct.

[swingtan]

In the E38, no.

In CL, the final AFR is controlled solely by the switch point set for the O2. While there is a table for this ( B1515 & B1516 ), there are missing calibrations still that result in these tables having no effect. So the actual switch point, or "rich/lean" crossover point, is fixed at a voltage that represents 14.63:1 AFR

Please note though, that altering the Stoichiometric setting in the tune will effect your PE fueling. PE fueling is calculated as an EQ ratio from the Stoichiometric setting. Altering the Stoichiometric setting by 0.5 AFR richer, will also move the commanded PE fueling by 0.5 AFR richer. This will occur with no adjustments made to the PE tables. So be careful if you decide to try leaning out the Stoichiometric setting, as you will need to richen up the PE settings to remain safe.

Simon.

[VEGASROBBI]

Exactly my observation, the E38 is obsessed with the O2 swithch point. Change fuel, offset MAF, change stoich settings, change O2 switchpoints, all have little to no effect; in CL the E38 will migrate to stoich for that fuel and look for the NB O2's to switch.

I've tried to modify the O2 signal with piggyback voltage and the E38 knows, gets irrational. I do not believe WB simulation of the NB will work correctly due to issues with the lo reference circut(as GMPX mentioned) as well as input from the rear O2's, cat temp and protection, etc..

Any chance of identifying the missing calibrations or create a semi-OL COS for the E38?

[Mark300]

Hi All,
Thank you for your help. The answers is a bit disappointing. I was trying to richen up to 14.00. I feel the car does not like 14.63 on high altitudes and hot temperature. It feels better on the throttle and less knock, lower chamber temperature.

Regards

mark