MAF vs. Airflow Freq Question

[JUSTINKP]

Ok probably a dumb question.

Looking over my recent scan, I'm running all over the place on my Short term fuel trims between -3 and +4. Long term fuel trims are -6.2 mostly.

If I understand this correctly, I'm running rich on the long term? - is rich, + is lean correct?

Doing MAF Calibration tuning, how do I know which Mass Air Flow Frequencies to change and how much by these fuel trims I'm seeing.

Stoich is at 9.70

[5_Liter_Eater]

- is rich, + is lean, yes. Short terms will be all over the place, long terms are a trend of short terms. You need to plot the LTFTs against the MAF table using a histogram. Then just copy and paste special (multiply by %) the percentages into the tune. Flash and repeat.

[JUSTINKP]

Awesome. Thats what I had read.

Now, I just need to figure out why my LTFT are not going into a histogram. I get the "Parameters are not supported" error when I bring up the LTFT histogram. The logs show on the table, gauges, chart, etc though.

Thanks for that help.

[5_Liter_Eater]

Probably because you do not have MAF frequency being logged in your table. The histo needs all the things you want to plot and plot against. So you would need LTFT and MAF Frequency at a minimum.

[BackyardTurbo_FTW]

If you aren't overly anal about that kinda stuff, just multiply the whole table by .94 to remove the -6 LTFT.

Or if you follow the MAF Tuning Thread, make a PID for LT+ST and then compare it to either MAF Calc table and do it the proper way

[JUSTINKP]

If you aren't overly anal about that kinda stuff, just multiply the whole table by .94 to remove the -6 LTFT.

Or if you follow the MAF Tuning Thread, make a PID for LT+ST and then compare it to either MAF Calc table and do it the proper way

My histograms still aren't working so I'm gonna try this. Thanks

[JUSTINKP]

I removed .94 from the MAF Airflow table.

Vehicle idles better now and seems to run smoother.

On the scanner, I'm running slightly lean so far. 2.0 to -.08 on the LT fuel trim but I only ran a short run on the scan.


The biggest issue I noticed was I'm getting knock now. Ugh.

[silverbullet08]

These motors are wierd about throwing false info out for the first 10-15mins of run time after a flash. You need to flash then drive aroud for about 10 mins then restart the logger and make another 10-15 min log. This always gives me the best results.

['09SS]

or if you can, drive more. then log say after 50-100 miles to let everything even out before you make changes again

[JUSTINKP]

How would I adjust the knocking above? In the spark tables I'd imagine?

Also, would too much, or too little timing be giving me horrible fuel economy?

I'm still using the stock timing with high octane (105 octane E85) so I'm guessing if I'd advance the timing a bit, I'd get some increased fuel economy due to making more power.

[thebucky84]

- is rich, + is lean, yes. Short terms will be all over the place, long terms are a trend of short terms. You need to plot the LTFTs against the MAF table using a histogram. Then just copy and paste special (multiply by %) the percentages into the tune. Flash and repeat.

how is this histo setup? Whats the plot value, X header and y header? Also from what you described is this the best way to tune your MAF without hpt pro using a wideband? I'm curious because i do not have pro and won't be able to get for some time.

[chood711]

After you set up a custom PID to add your STFT's to LTFT's, you will plot that against the MAF Airflow vs Output Frequency table. Is you stoich really set at 9.7?

[thebucky84]

so i've been MAF tuning lately and seems to be going nowhere? Do i need to reset my fuel trims or something? I have a histo setup for AFR error against the maf and every time i go for a log i seem to be getting the same numbers (-1.17) pic is posted below. After I'm done logging i go into the editor and paste multiply % against the maf. Seems for the past 4 logs i keep getting the -1.17 in those cells every time. Is this just a matter of taking awhile to smooth out?

As for the histo, I'm using my ac switch to log AFR's. This is the equation I'm using for the histo: ((([PID.7101]/(5/8.5))+10)-(100*([USER.7101]-[SENS.121])/[SENS.121]))/(100*([USER.7101]-[SENS.121])/[SENS.121]).... Basically (Actual - Commanded) / (Commanded)

[5_Liter_Eater]

That looks to me like you are actually getting the AC pressure signal back to the PCM, not the wide band. Something is not wired right.

[thebucky84]

the afr's are reading correctly on the scanner. The scanner matches the wideband and everything.



here is my AFR Commanded:




and AFR Actual:

[5_Liter_Eater]

Maybe a problam with a custom afr error pid. Post your vcm scanner.cfg, your config and a log.

[laser_racer]

Reading from that sensor you have to unplug the ac right? Bucky did you make a custom pid to convert your afr readings so it's using gas readings?

[thebucky84]

Well heres the pid im using: ((([PID.7101]/(5/8.5))+10)-(100*([USER.7101]-[SENS.121])/[SENS.121]))/(100*([USER.7101]-[SENS.121])/[SENS.121]).. (Actual - Commanded) / (Commanded)... I'll have to post my scan file when i get home, but the pics on post #15 are from the most recent log i made which was last night.

Laser you do not need to unplug your ac switch if you have the wire going to your ecu disconnected with quick disconnects. Since your wide band is now going to ecu the computer sees no signal from the ac. All you have to do is adjust your fan settings so they're not on all the time at 100%.

[thebucky84]

Maybe a problam with a custom afr error pid. Post your vcm scanner.cfg, your config and a log.

Here are my files

[5_Liter_Eater]

need the "VCM SCANNER.CFG" file too. It contains your user defined PIDs.