I noticed jn2 in another thread experienced something similar to what I have found - if Flex Fuel is enabled on a non-FFV vehicle, the LTFT no longer displays (no data). STFT still works fine. Has anyone else encountered something similar and found a fix?
LTFT works fine on my 2020 Mustang 5.0 10R80 flex tune. After a flash, LTFTs show something other than zero after a short drive to learn the alcohol percentage, etc. According to my last log, that was around the 14 minute mark. I use "Long Term Fuel Trim Bank 1" and "Long Term Fuel Trim Bank 2" to log. Both non-SAE parameters.
It does not work on mine. I've been driving for days and LTFT Bank 1 and 2 stay 0. STFT 1 and 2 fluctuate as normal, as does actual and commanded lambda for both banks. The inferred alcohol percentage and stoich also adjust almost immediately. Looking at my change logs this started with flex fuel being enabled. I never use SAE PIDs/channels.Originally Posted by radar doc
Just a guess, but the inferred alcohol % is probably taking the place of LTFT since it's basically doing that function anyway.
Internally it's probably actually using the LTFT variable for the flex and on newer (or different) strategies it's probably splitting up the calculations.
IT happens to me sometime. after a long enough drive they come back on.
are you adjusting all of the tune for flex or just toggling the flex on and thats all?
I've adjusted all of the tables that I could find. Is there something in particular you're suggesting I look at?
My inferred alcohol percentage begins learning immediately but takes about 15 minutes to reach matured status. Might be worth submitting a support ticket to HPTuners. Could be a simple code change needed in some strategies.
I noticed my inferred alcohol percentage varies throughout a drive. It can be as low as 64% to 66% and then as high as 77%.
Looking at my logs, I noticed that when I enabled Flex Fuel, the LTFT was reporting but I must have cleared all PCM defaults using FORScan at one point because the logs after that one no longer had LTFT data. I've done this clear PCM function before on my N/A 3.5 Explorer and the LTFT eventually populates but never took this long to do it.
Would it because I am running E85 right now and the inferred alcohol fluctuates preventing LTFT from populating?
Last edited by metroplex; 09-20-2021 at 08:21 AM.
If your inferred alcohol is fluctuating, I don't think your LTFTs will be active.
After learning, my inferred alcohol percentage locks to a value and stays there until I refuel, flash a tune, or perform a KAM reset. I haven't noticed it change from that value once it's matured. After the Inferred AFR Status shows Matured, the LTFTs start doing their thing. On a side note, I've been working with the knock octane modifier recently, and like LTFTs, it doesn't seem to populate any spark corrections until the alcohol percent is matured.
In the VCM scanner, I monitor:
Inferred AFR Status: Reads Actively Learning, Paused or Matured. Do you have this PID on your platform?
Inferred AFR Source: Reads Refueling (after a refuel) or Fault Exit (after a flash or KAM reset)
Alcohol Percent
I haven't used ForScan on my car. I have OBDLink MX+ with an app on my phone for quick checks, KAM resets, etc.
While transitioning to E85, I filled the car with various amounts of E85 to watch the learning process and it behaved like I said above. I'm at 79.6% alcohol at the moment and that is where it has been since the last fill-up (after the 15 minute drive to mature).
Might be apples vs oranges depending on what you're tuning, but here's my Mustang flex fuel tab with my current settings (blend curves from F150):
flex tab.JPG
I'm interested in your solution as I'd hate to flash a tune one day and lose LTFTs (or any other function).
The only main scalar I am missing is max update rate. There are some tables on the right that I don't have, but it could be because of your split injection/PDFI. I used the stock FFV values on actual Flex Fuel Fords. I know theoretically E85 is 9.85 but Ford seems to use 10.26. I am not sure if this makes a difference in whether LTFT is reporting. I do know that when I had flex fuel enabled and LTFT was reporting, that my STFT was within norm. Same goes for now with zero data for LTFT. now if STFT were wildly out of swing like I have seen in the past on other Fords where I filled with E30-E50+ without adjusting the stoich enough.
I have those PIDs in VCM scanner and will start looking at them.
BTW I use FORScan because there are a lot of functions that are the closest we can get to IDS / FJDS without paying the fees for IDS/FJDS. I run an OBDLink EX, I used to use my MX but the Bluetooth was woefully unstable. Whenever I reflash the PCM, there are a bunch of DTCs set from modules due to the bus disconnecting from them. So I use FORScan to clear those DTCs. I also use FORScan to monitor Mode 6 data (especially for misfires and specific cylinders, etc...)
From the info for Mustang tunes I've seen on this forum, the max update rate must not be zero, so that may be something you can ask HPTuners to add (?) I think that is the root cause of the missing LTFTs, since your alcohol % doesn't seem to be maturing.
I think you're good using 10.26 also.
I noticed the bus faults also and that's one of the reasons I bought the MX. So far, so good with mine.
Last edited by radar doc; 09-20-2021 at 12:18 PM.
What do you have for the Ethanol % vs AFR table? Just 9.0 = 100% and 14.6 = 0%?
Absolutely. I've read it's not a good idea to try to outsmart Ford on this.
Minor point...the "14.6" is actually "14.64" (you can see this if you copy/paste the table with axis to Excel, Word, Notepad, etc).
Yes, I remember that from the good old days of pre-07 Ford tuning! I'm also tracking that on my other spreadsheet I use for calculating percentages of ethanol.
I bet this is why my inferred alcohol only maxes at 75%-77%. I'll give this a try.
Also the high end AFR range setting of 13.08 is what Ford uses on its flex fuel vehicles. Should this be changed to 12.55 or so? The way I figure is that if you're running full E85 (9.85) and swing 25% lean with a different mixture, it would be 12.55 or so otherwise the 13.08 would be excessively rich for it to switch over?
Last edited by metroplex; 09-23-2021 at 10:11 AM.
Are you still using 10.26 for Stoich AFR Min? That is about 78% on my spreadsheet derived from the Ethanol % vs AFR table:
ethanolvsafr.JPG
So my thought process for the values I chose for the flex fuel tab come from this spreadsheet.
I have a spreadsheet with similar values as well.
Also the high end AFR range setting of 13.08 is what Ford uses on its flex fuel vehicles. Should this be changed to 12.55 or so? The way I figure is that if you're running full E85 (9.85) and swing 25% lean with a different mixture, it would be 12.55 or so otherwise the 13.08 would be excessively rich for it to switch over?
As I understand it, when the Inferred AFR hits the Low AFR Range, the computer snaps/locks to using the Low AFR Endpoint for its calculations. This should happen when I fill up with E85 after running E10. So with my numbers in the flex fuel tab, if I fill up with E85, the AFR will begin at 14.08 and slowly drop during the learning process. When 10.69 AFR (E70) or lower AFR number is reached, the computer will then calculate using 9.85 (E85).
Same with High AFR Range and High AFR Endpoint when you add E10 (or "E85" with less ethanol). So if I have E85 in the tank, almost empty and then fill up with E10, once the Inferred AFR reaches 13.08(E28), the computer will snap/lock to the High Endpoint of 14.08.
In your example, if you were at 9.85 (E85) and added enough gasoline to just reach your High AFR Range of 12.55 (with High Endpoint of 14.08), the computer would use 14.08 for stoich. So instead of calculating based on 12.55 AFR and associated inferred alcohol content, it would be calculating based on E10.
I think the Ford flex fuel logic is a compromise between learning speed and inferred alcohol accuracy, available fuel and of course staying within mechanical limits.
I'm certainly not a "know-it-all" and welcome any corrections to my thought process.
I get that, but I'm thinking you're say at 13.00, it will not latch to 14.08 and you'll be running like 33% richer and might set off the STFT/LTFT limits? I believe 25% is the threshold for the fuel trims.
After alcohol learning is complete, if the Inferred AFR is 13.00 and the High AFR Range is 13.08, I believe the computer flex fuel logic will use 13.00 for stoich. STFT/LTFTs should be near zero.
If Inferred AFR is 13.00 and the High AFR Range is 12.55, then the computer will use the High AFR Endpoint of 14.08 for stoich. STFTs/LTFTs will need to compensate quite a bit.
This raises the question for the effect of widening the window between High and Low AFR Range to allow the flex fuel logic to be more accurate, but I think the answer is related to the alcohol learning speed vs accuracy compromise.
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