Could use some help(commanded afr, maf tuning)

[floppynuts3333]

Ok, I have been reading my butt off and am trying to get get caught up on tuning. I am tuning my 07 tahoe w/ afm to gain some economy. So far I have adjusted the DOD(AFM) settings with some small gains. I adjusted DFCO to stay in a bit longer. A couple of things I am confused on...I read in one thread that adjusting the 02 rich/lean vs. airflow voltages lower to go along with the mode vs. airflow would help run a bit leaner in CL. I set some cells to 350(450 stock). After logging avg 02 voltages they are nowhere close to the 350mV settings in any of my cells. I changed the mV setting to 550mv to see if this made a diff. and there was no diff in comm afr or avg 02 voltages.I was wondering if the stoich afr conflicts with this voltage in CL? Or basically how do the stoich values really come into play? (I have flexfuel with the diff stoich values based on eth. content) I notice my trims have been negative, I reset the trims and still LTFTs stay negative. Will they stay negative or adjust themselves with this diff setting?

2nd question is..I logged commanded AFR today for the first time and for almost the whole log the comm. AFR was 11.2 and only momentarily went to 14.67 a couple of times. Why is the comm. AFR soo rich in all regions, even cruise?
Can someone please help with some of these questions!!
I could also use some guidance on where to start my other tuning. I have read how to VE tune and maf tune PE and OL and CL. I have read so much that I kinda confused myself. I have a MAF and want to stay using the MAF. Won't the MAF be used in all situations except for failed MAF? IF so there is no reason to tune VE table if I am not going to disable the MAF correct? I used the EQ>>VE program to create my VE table based on all the equations...It seemed to transfer and make the VE table fine but the 3D graph has a crazy valley in the upper middle portion.(I will worry about that later after I determine if I really need to mess with the VE table).

I am looking to get the NGK WB soon to help out. I read a write up that basically has me log MAF freq vs. STFTs then ajust the MAF calibration while maintaining the smooth curve. Is this what I should do first? I am trying to get whatever I can using the NBs first. I appreciate everyones help. I would love to master tuning but could use some guidance. I have attached a recent log and my calibration. The log is jumpy at first because I was trying to hit all of my MAF freq cells.... Thanks again.

[Xjas]

Just a guess here, does your vehicle have a fuel composition sensor? It looks to me like the commanded EQ ratio is most of the time 1.00 (lambda) so the ECU is commanding stoich but your ECU thinks your fuel is ~25% alcohol (ethanol) (from your Stoich AFR table) so it has adjusted stoich accordingly...

[floppynuts3333]

I believe it does since this is how the computer would know when I'm running E-85. I have only ran one tank of E-85 in it and that was like 10 tanks ago. I ran it dry before filling it up again with regular gas. I do not plan on running E-85 again. I was wondering if I should change all of the stoichs to regular(10%) gas. Or even put them to the slightly leaner value I want to run anyway.I realize I would have to take this into account if I do any more adjustments.. this method had already been called a hack tune on here by some. I could definitely use some good advice on this.

[Xjas]

If your fuel is 10% but your ECU thinks its ~25 then the sensor may be faulty.

[flame]

The newer vehicles don't use an actual sensor anymore. It is a "virtual" sensor using pcm calculations. Click the pic for the description of the system.

[floppynuts3333]

Thanks for the info.
That is interesting...I wonder if changing the O2 voltage from the stock 450mv to 350mv actually made it start registering a different percent alcohol? Would you guys still recommend setting all of my stoich values to 14.7ish if I only plan on running gas and no E-85. I am wondering what actually controls the fuel trims in closed loop...is it the reference crossover voltage of 450mv setting in the closed loop section or is it the stoich values that are put into the AFR table?

[flame]

I would say your best bet would be to reset the ethanol content reading. Set the stoich for the fuel you are going to use and tune it for that.

[Xjas]

The newer vehicles don't use an actual sensor anymore. It is a "virtual" sensor using pcm calculations. Click the pic for the description of the system.

Very interesting info, when did that take effect?

I noticed that document states after an ECM/PCM replacement or the alcohol content learning has been reset the vehicle needs to be run on a tank of less than 10% alcohol, presumably for ECM to get a baseline for regular gas to work from since it uses LTFT and STFT to calculate change in alcohol content from previous tank rather than actual alcohol content. The OP mentions he has put one tank of E85 though the vehicle, if he has performed an ECM reset with this fuel in the car the ECM calculation for alcohol content would be way off as the E85 fuel would be the baseline used by the vehicle, not likely to be the case IMHO but it is a possibility.
Interesting to note from that article also that the ECM uses fuel tank level changes to decide when to recalculate alcohol content, fi you have a faulty fuel level gauge the ECM may not recalculate alcohol correctly either.

[flame]

Very interesting info, when did that take effect?

I know they still used a sensor in 2005

[floppynuts3333]

I am going to wait a couple of more fills, if it doesn't change I am just going to set all of the alcohol percentage stoichs to the value I want. I will probably never mess with E-85 again. But this does bring up some good info that may help if I decide to run a water meth kit.

Is there any reason to tune my MAF? I am stock with K&N CAI.

Can someone please help shed some light on when VE would actually come into play if I keep running a MAF? I know if my MAF fails...but does it use the VE tables for PE or any times when MAF values are not representative of actual engine air flow.. like coming off throttle etc.

[flame]

Definately tune the MAF any changes to the intake tract will affect it. VE is blended with MAF readings below 4000rpm then MAF only above 4000.

[floppynuts3333]

Thanks flame.

[floppynuts3333]

I adjusting the 02 rich/lean vs. airflow voltages lower to go along with the mode vs. airflow would help run a bit leaner in CL. I set some cells to 350(450 stock). After logging avg 02 voltages they are nowhere close to the 350mV settings in any of my cells. I changed the mV setting to 550mv to see if this made a diff. and there was no diff in comm afr or avg 02 voltages.I was wondering if the stoich afr conflicts with this voltage in CL? Or basically how do the stoich values really come into play? (I have flexfuel with the diff stoich values based on eth. content) I notice my trims have been negative, I reset the trims and still LTFTs stay negative. Will they stay negative or adjust themselves with this diff setting?

Anybody have any insight on this for the gen IV pcms?

[floppynuts3333]

anybody?

[IDRIVEAG8GT]

Floppynuts <----- That made me lmao. No further input.

[floppynuts3333]

haha...at least I got a response