Commanded AFR is Stoich

[randall c]

I've spent the last three weeks lurking around here trying to get my head wrapped around this EFI stuff and have picked up a lot of good info, so this morning I tried logging for MAF modeling. I can't seem to get commanded AFR to match my PE tables. Commanded stays @ 14.7. I thought all I had to do was set dynamic airflow enable/re-enable to 1/0 then commanded AFR would read off the PE table??

Attached are the tune I used & the log file.

Thanks!

[ct06gto]

I've spent the last three weeks lurking around here trying to get my head wrapped around this EFI stuff and have picked up a lot of good info, so this morning I tried logging for MAF modeling. I can't seem to get commanded AFR to match my PE tables. Commanded stays @ 14.7. I thought all I had to do was set dynamic airflow enable/re-enable to 1/0 then commanded AFR would read off the PE table??

Attached are the tune I used & the log file.

Thanks!

The dynamic airflow tables disable speed density. In other words your reading from your maf calculations only. To enter pe you need to reach a certain tps and map kpa amongst other tables. You will see your commanded afr go from 14.7 afr to 12.6 afr (in your case) when your in pe until then you will comand stoich.

[Cantalope Kid]

To tune your MAF: You need to disable several adders that are screwing up your figures as well...i.e. Using the editor turn off LTFT's, DFCO, CFCO, ect. Reset your fuel trim values using the scanner before you start logging again. You also need to be scanning the MAF flow hertz high/low frequency AFR error % so you can copy/paste the data into the MAF tables in your tune accordingly.

[randall c]

To tune your MAF: You need to disable several adders that are screwing up your figures as well...i.e. Using the editor turn off LTFT's, DFCO, CFCO, ect. Reset your fuel trim values using the scanner before you start logging again. You also need to be scanning the MAF flow hertz high/low frequency AFR error % so you can copy/paste the data into the MAF tables in your tune accordingly.

Thanks for the replies.

Do I disable LTFTs with LTFT Boundries? I now have DFCO, CFCO taken care of (I think), I also maxed out the temps on CL Enable, anything else?

I was logging the low freq MAF, the chart wasn't set up properly to show it. I used a histogram from the repository to get low freq AFR error % it seemed to be working properly. I'll try again tomorrow.

Any other suggestions are greatly appreciated!

[bluegoat06]

The reason why you're looking at 14.7 is because you're running in Cloose loop operation, and the NB's are doing what they're supposed to do. you won't hit PE until you meet the criteria (MAP, TPS, etc) per your power enrichment values. in simple terms, while not in PE, the PCM would relay on the 02 sensors to keep stoich, (14.7afr unless otherwise commanded), and when it moves to PE, example: you go WOT(you don't have to be WOT to enter PE) , then it's uses the PE table to command your fuel. because PE is nothing but a targeted AFR, you would need to actually calibrate your MAF tables so the airflow values read by the MAF sensor would get translated the right way and the PCM would be able to perform accurate fuel calculations.


Since you have disabled VE lookups setting your dyn air to 1 and 0, you'll be tuning the MAF only. VE would be out of the equation from here on, until your turn back those settings to tackle VE if you wish.

You can tune your MAF with your NB's from the 3550hz or lower if your cam would allow you to do so at idle, up to 7600-7800hz using CL-MAF with STFT's only. (LTFT's disabled)

To disable LTFT's, go to engine/fuel control/ol cl/long term fuel trims ltft enable, and set the min ect value to its max (493F) and set the max ect value to its min (-40F). no need to disable the boundaries if LTFT's are disabled.

To disable DFCO and CFCO, max out the temp and rpm values where temp or rpm needs to be above certain temp or rpm, if they have to be below, just use the least min setting allowed to do so.

You can use my config file to start, check histogram 4 and 5 for MAF using STFT's, (Use Histo 5 up to 7800hz using NB's, avoid entering PE) shoot for -2% +2% error. remember that we have 2 MAF tables to deal with, but for the PCM,it looks like a single one, so whatever value you'll find for the 5800hz cell, in the MAF lo table, type that value in the 5800hz cell, on the MAF hi table.
Don't bother with that cell when you're doing MAF hi table. you'd only want to reference that cell when tuning the MAF lo table.
It'd help a lot to do this tuning on the freeway since traffic and constant stops and go would screw up your readings. modulate your gas to hit all the cells.

When you're done with the MAF using the NB's, you can use Histo 10, from 8000hz and up to dial the MAF using your WB. (note that'll need to change the WB pid to match the WB you have). you will have to disable your STFT's and run OL-MAF only, or you can choose to disable close loop using the vcm scanner,your choice, and dial the MAF using your WB from 8000 hz and up.

Once you're done with the MAF, then leave the LTFT's disabled, and re-enable your DFCO and CFCO settings putting them back to stock. you can watch your STFT's with histo 4 and 5 for sanity checks from time to time, and your WB for WOT.

Have fun

[randall c]

...
Have fun

Thanks D. I appreciate it.