LNF STFT and LTFT Tuning

[BackyardTurbo_FTW]

Ill re-write this later with screenshots.

1. Make a Custom PID to add the LTFT's to the STFT's. ([PID.6]+[PID.7], I think)
2. Add that PID to the Tables List
3. Goto Histograms and then click on Settings
4. Make a Histogram and chose that Custom LT+ST PID
5. Click on the right tab and use the Maf Frequency Sensor
6. Insert all of the values listed in HPT Maf Freq table starting at 10417 and going all the way down. Make sure to comma separate each and don't use ANY spaces between the values!!!
7. You will have to split it up into 3 parts at least, it would be easy for you to match it to the spreadsheet and just copy/paste the values from there to cheat lol
8. Then make another Histogram and chose LT+ST PID again
9. In the right tab, this time you want to chose Load and Engine Speed as the sensors to compare to
10. Then input the RPM and Load values from the MAF Correction table (or Copy/Paste from Spreadsheet again)
11. Repeat the process making a 2nd set of Histograms using LTFT alone vs Maf Freq and then STFT alone vs the Maf Corr Table.


How to Tune MAF in stock location:
*Set the entire Maf Correction Table to 1's.
*Unplug the Purge solenoid and flash the car!!
*Warm up the car, drive it a lil until you reach operating temp, then start logging.
*Do a mix of driving between city, highway and pulls, 1 LOG!!!! do not split it up!!!
*Then goto the Histo's for LTFT+STFT vs Maf vs Freq and copy/paste over that table in HPT using Paste Special multiply by %
*Then flash that to the car, warm up and drive
*Log again doing the same method above, you want to try and hit as many load cells as possible and multiple times too
*Then again, copy the Histo data for LTFT+STFT vs Maf vs Freq and do paste special multiply by 1/2% this time
*Flash, warm up, drive, log. The LTFT should have settled into +/-1% by now
*Now using the STFT vs Maf Correction Histo after a long drive again, select the whole table and paste special by 1/2% over the MAF Correction tables.
*You may or may not need to do this twice but after this step the LT should be +/-1% and the ST's should be under 3-4% at anytime.
*After the trims are stable plug the Purge Solenoid back in!


Everything at that point should be pretty close when you look at those histo's. If a cell or 2 is 3-4% or higher, just do paste special by 1/2 with those cells and repeat the flash/log process.


How to tune the MAF in the lower charge pipe:
*Set the entire Maf Correction Table to 1's.
*Flash the car and unplug the purge solenoid!!
*Warm up the car, drive it a lil until you reach operating temp, then start logging.
*Do a mix of driving between city, highway and pulls, 1 LOG!!!! do not split it up!!!
*Then goto the Histo's for LTFT+STFT vs Maf vs Freq and copy/paste over that table in HPT using Paste Special multiply by %
*Then flash that to the car, warm up and drive
*Log again doing the same method above, you want to try and hit as many load cells as possible and multiple times too
*Then again, copy the Histo data for LTFT+STFT vs Maf vs Freq and do paste special multiply by 1/2% this time
*Flash, warm up, drive, log. The LTFT should have settled into +/-1% by now
*Now using the STFT vs Maf Correction Histo after a long drive again, select the whole table and paste special by 1/2% over the MAF Correction tables.
*You may or may not need to do this twice but after this step the LT should be +/-1% and the ST's should be under 3-4% at anytime.
*If there is spots in the Correction Histo that are over 5%, JUST adjust those spots now!
*After the trims are stable plug the Purge Solenoid back in!


Note:
Ive found if the trim is WAY off (like +/- 10%) it stops trimming and just goes off the table value and creates a AFR error without adjusting for it. With the blow-thru style this will create a headache and will likely throw a MAF code and system too rich/lean code because the STFT's will be like 20-30% when you start! When they go that high, the VCM can no longer compensate enough to bring the AFR into check and the car will NOT run the commanded AFR! So be patient when tuning for this style of MAF location!! I ended up using the LT+ST vs Maf Freq histo a few times to get that portion just right, I then moved onto ST vs MAF Correction table and just adjusted the spots that were over 5%. Pay attention when tuning WOT to see if the car stops the ST Trim during your pull!! If it does this, notice where it went just before it stopped trimming and at what MAF Freq, then adjust those cells accordingly and it will come into check quickly!


I know for myself, it's cool and damp in the morning and warm and dry in the afternoon. This spreadsheet I made up will allow you to take a log in the AM and then in the PM and average the results from the 2 logs by just copying and pasting the info into the spreadsheet. All the calculations are setup, just input AM in Log 1 and PM in Log 2, then copy the results from the Averaged Results at the bottom and paste special/multiply by % over your tables in HPT

BYT Ultimate Fuel Trim Spreadsheet!!
(PS, check the tabs, it does the Frequency table AND the Correction table )

Another version of the Fuel Trim Guide courtesy of Shabby. Compacted to 3 rows and includes every cell in the Maf Freq Table.
Shabby Modded BYT Guide



Side note on things Ive noticed:
It seems like the car looks to the STFT values for a "trend". As it sees a certain amount of + or - values it then starts to adjust the LTFT in the direction of MOST of your STFT values. So if you are getting a lot of -10%'s on your new intake and a few + STFT%'s here or there, it will make the LTFT gradually start heading toward your -10%. So if you've just made a major change to the intake system or MAF location you want to drive the car a good 20-30 mins BEFORE trying to adjust ANYTHING!!!! You will see the car "stabilize" a bit and start showing some real readings! If you rush it you will surely end up chasing your tail. When you see the car start to stabilize and react normally, restart the logger and begin your tuning


After the discussion about unplugging the purge solenoid and how it freezes the LTFT, I decided to try and use that to our advantage. Sure enough, it works like a dream!! When you flash the car the LTFT and STFT sit at 0 until the Cat temp comes over ~500*. So this locks the LTFT at 0 and you just watch what the actual trims are doing. On a 3 hr/way trip over the weekend and logging the whole thing:
*LTFT actually sat at 0 most of the time after plugging the purge solenoid back in!
*STFT didn't go past +/-3%!
*LT+ST vs Maf Freq table was like +/-.5%!!!!
*ST vs Maf Corr table had only a couple +/-1% spots!

Car drove incredibly smooth and I was commanding 20* up top while running a 25psi tune

[Terminator2]

The absolute best method and fastest method to tuning the STFT and LTFT is to make a histogram of LTFT + STFT vs MAF frequency and another histogram of LTFT + STFT vs the MAF correction table. That way you are not chasing your tail so much. The LTFT and STFT can sometimes cancel each other out or they can really add up to a very negative or very positive number.

[BackyardTurbo_FTW]

Using this method I haven't had a wacky LTFT afterward. If you do it on long drives and take the averages of EVERYTHING it works out well. Def putting miles on it between tuning each helps greatly! The car seems to "settle" a lil differently after some miles. I usually tune out the LTFT, drive it for awhile, then log for STFT and repeat until everything is right on the money.

Ive read about your way a couple times now from what you've posted here or there. Im going to flash a stock Freq and Corr table back and try your method, just to see if it's easier or better and which is quicker etc.. Do you have a CFG with your Histo's loaded?

[Terminator2]

Using this method I haven't had a wacky LTFT afterward. If you do it on long drives and take the averages of EVERYTHING it works out well. Def putting miles on it between tuning each helps greatly! The car seems to "settle" a lil differently after some miles. I usually tune out the LTFT, drive it for awhile, then log for STFT and repeat until everything is right on the money.

Ive read about your way a couple times now from what you've posted here or there. Im going to flash a stock Freq and Corr table back and try your method, just to see if it's easier or better and which is quicker etc.. Do you have a CFG with your Histo's loaded?

Yes, I do. I find it much easier that way because when you add the two together you get a better picture of what is really going on. You can have a LTFT of +10 overall but sometimes the STFT in some cells is -10 so the total fuel trim is zero in that cell. If you had taken out fuel in that particular cell by tuning off LTFT only you would have to adjust it back up next time so in a sense you are sometimes chasing your tail.

[MMGT1]

In your VCM's guys cant you "turn off" LTFT and just use STFT to tune your car? STFT's are instant and LTFT's are a "learned" value. I would say that the [SENS.114]+[SENS.116] or turn off the LTFT's and use STFT's only. I got great results using the LT's and ST's to tune.
Just a heads up, when you make adjustments to sections of the fueling, smooth the section. Just highlight the section you have adjusted and "smooth selection". This will take a few times to do, but if this is for your own car it will come in line, again it takes a while to do it this way. I used to run with a "tuned, choppy" table for fueling, but knew it could not be right. In my mind the tables should be smooth and no dips. Put enough time into it and you can make a table without peeks and valleys. For example, my MAF table is now as smooth as the origional and am within .1 of commanded AFR! I would say this will hold true for your correction table. Smooth selection as you go and eventually it will come in line!!
Something else for you guys. Are you using a NB to tune cruise and a WB to tune PE? If you use a WB to tune cruise all that will happen is your NB, when reinstalled, will "adjust" your fueling to what it thinks is your stoich value! This, in turn, will throw your tune in PE out the window! I use the NB to tune up to the switch point, and WB to tune the PE sections. This way you have 0% adjustment happening when you go into PE, and the car will fuel the way you tuned it. If you are going open loop, forget everything I just said and use your WB to tune the entire table.... lol

[BackyardTurbo_FTW]

There isnt as many options as some of the other cars. I dont believe we have a way to shut off the LTFT's.

[MMGT1]

That being the case, give the LTFT+STFT method a try. You'll like it Im sure!

[BackyardTurbo_FTW]

Yea, he's sending me the histo to try out now! Im going to do it that way with a fresh start on the freq and corr tables and then post a writeup for it. Ill get some logs posted too to compare the results for each and see how they perform!

[oopsitouchedmyself]

thanks for the info! i'll be trying some of this out tomorrow i believe.

[BackyardTurbo_FTW]

Im going to post the way Term/Broke do it during the day. I haven't fully tested it yet but Im liking what I'm seeing so far. It requires some manual setup but its honestly very easy. I will of course do it with screenies to make it fool proof

[Terminator2]

That being the case, give the LTFT+STFT method a try. You'll like it Im sure!

We cannot shut off LTFT on this ECM currently so using the LTFT + STFT to get the total fuel trim is the best method IMHO.

[383_Stroker]

If you happen to close the logger and reopen your file, you will need to press PLAY and let the whole thing run again. This will repost the changes to the Histo chart. If you don't do this you will see only a couple values here or there in the chart!

Right Click... Load all Data?

[BackyardTurbo_FTW]

O damn! Thats much better and faster LOL...

[383_Stroker]

lol.. I pounce on those rare moments where i have a little nugget of information to offer :-D

[BackyardTurbo_FTW]

That was some solid info to add too! LOL. Updated the 1st post, thank you

[oopsitouchedmyself]

so is this the new and improved version of the STFT and LTFT's?

[BackyardTurbo_FTW]

Im currently using the other method, Im just testing it out and making sure I have it all right before I post all the info. Prolly later today it will be up. Either method seems to have ended up working the same, just different ways to get there

[BackyardTurbo_FTW]

Updated 1st post

[oldskool]

Another great write up. I understand that you want the LTFT's slightly negative. I understand how to get them there. But I'm curious why we go through so much painstaking trouble to do this.

Our car runs fueling off the WBO2 sensor - only if it fails will the MAF become the primary determinate of fuel right? Put in otherwords, it takes feedback from the WB sensor to acheive the commanded AFR, and it's quite good at it. I set up an AFR % Error PID, and its rarely outside of 3%, excluding DFCO. As long as your LTFTs are slightly negative and there are no obvious fallacies, why go through such trouble to get them perfect? This is assuming the intake diamter has not changed. I'm really asking a question here, by the way, not trying to state what i think are facts.

[Terminator2]

Another great write up. I understand that you want the LTFT's slightly negative. I understand how to get them there. But I'm curious why we go through so much painstaking trouble to do this.

Our car runs fueling off the WBO2 sensor - only if it fails will the MAF become the primary determinate of fuel right? Put in otherwords, it takes feedback from the WB sensor to acheive the commanded AFR, and it's quite good at it. I set up an AFR % Error PID, and its rarely outside of 3%, excluding DFCO. As long as your LTFTs are slightly negative and there are no obvious fallacies, why go through such trouble to get them perfect? This is assuming the intake diamter has not changed. I'm really asking a question here, by the way, not trying to state what i think are facts.

That wideband is not as effective as you might think. I gained a ton of torque and HP dialing in my MAF perfectly so the A/F does not dip when you first go WOT or ever up top like I have seen even. Every log I have seen even with the stock intake has shown a really rich spike when you first go WOT. Even the STFT is not fast enough to correct for things like that. The only way to fix it is a ton of logging and making small changes.