MAF tuning via FT's

[jonnycatz]

I'm planning to set my tune to be MAF only. I have read some use STFT's only, others use LTFT's only, and then there are some who will scan LTFT + STFT simultaneously and and make correction to MAF Hz table.. I assume trims definitely must be reset before scanning, as well as DFCO, COT, and DOD disabled. Afterwards, some will disable or enable LTFT's afterwards, not sure why LTFT's are not wanted except for changes they can make when entering WOT. This vehicle is a daily driver that honestly, will not go into WOT very often during my time with it. Any expert advice on differences between scanning with LT, ST, or LT+ST and disabling LTFT's after MAF closed loop tuning. "Wideband" part throttle tuning is not an option as I use a tailpipe sniffer and will only use it for WOT tuning.

[ingsteve]

wideband is mandatory for wot tuning.
For idle and part throttle you can tune with trims.
Scan and see your LTFT, if they are below +-10 you can disable LTFT and tune only with STFT, it will be very quickly because you don't have to wait the LTFT relearn that tipically is after 100miles to be accurate...use always multiply by %-half to avoid overcorrection.
After all STFT are +- 2-3% i would stop the tuning , re-enable the LTFT and check. It is better to complete everything in the same day.

[jonnycatz]

Thx for reply. So I will disable LTFT's and flash before running scan. When I "reset trims" before running scan, does it reset the LTFT's also even though they are currently disabled in the tune? Hopefully it does.

[Iam Broke]

yes.

[10_SS]

Also make sure you wait until your car is good and warmed up before you start scanning, if you don't then you will see the not quite warmed up values being overwritten by the warm steady state values as you analyze the corrections later.

[rcwilbur]

Quick question here. After disabling the LTFTs in the tune, do you still need to reset the LTFT's to zero through the scanner before logging data.

Put another way, if you disable the LTFT's, then start scanning and see that the LTFT's are postive, will the PCM use those positive trims when calculating fueling?

[ingsteve]

It is better to reset so you don't have to raise the question and you are sure th ecm do not add any fuel

[rcwilbur]

It is better to reset so you don't have to raise the question and you are sure th ecm do not add any fuel

I agree, but I already tuned my VE tables and they came out very good. Then tuned Maf and it looks good. The AFR is very good for both stoich and at PE 12.6, but the histogram of LTFT + STFT does not look so good, but maybe they will "learn out."

I'm thinking I should have set reset trims prior to logging data and may need to redo the tune.

[DSteck]

Trims reset every time you flash. You should be good to go.

[rcwilbur]

Trims reset every time you flash. You should be good to go.

Thanks. My log still confuses me a little. I ran 5 logs over the weekend to tune VE and the histograms showed the exact same LTFTs for every one of the 5. Attached is the last log--showing LTFTs ranging from 4 to 6. It doesn't look like it was resetting and I cannot tell if it is being used.

[rcwilbur]

Not sure why the LTFT's show up in the histogram, but in any event the LTFTs seem to be learning out as I drive the car. After about 75 miles they are starting to come down.