MAF/Fuel Trims Question - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

czellers · 02-11-2021, 01:14 PM

Question regarding LTFTs. Per the statements below from the following post [ https://www.ft86club.com/forums/showthread.php?t=64790 ] :

"The correction applied by the ECU due to the O2 sensor input will be in the form of STFT, if the STFT stays negative or positive consistently for a period of time it will be written to LTFT. There are several bands of LTFT based on MAF sensor flow rates (roughly related to engine RPM) where the ECU stores the LTFT."

So my question is, regarding LTFTs specifically, does disconnecting the battery wipe the stored LTFT data, or is it only "stored" for that drive cycle or until the "stored" data sees a specific delta/change, and is subsequently overwritten?

tomm.brz · 02-11-2021, 01:34 PM

disconnecting battery resets like an ecu reflash, LTFT will stay at 0 for a while , and after a bit of driving in closed loop the ecu will start learning LTFT and when it starts it never stops learning and updating the values

02-11-2021, 01:14 PM	#1
czellers Senior Member Join Date: Dec 2020 Drives: 2K19 GT86 Location: Raleigh NC Posts: 178 Thanks: 83 Thanked 39 Times in 31 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	MAF/Fuel Trims Question Question regarding LTFTs. Per the statements below from the following post [ https://www.ft86club.com/forums/showthread.php?t=64790 ] : "The correction applied by the ECU due to the O2 sensor input will be in the form of STFT, if the STFT stays negative or positive consistently for a period of time it will be written to LTFT. There are several bands of LTFT based on MAF sensor flow rates (roughly related to engine RPM) where the ECU stores the LTFT." So my question is, regarding LTFTs specifically, does disconnecting the battery wipe the stored LTFT data, or is it only "stored" for that drive cycle or until the "stored" data sees a specific delta/change, and is subsequently overwritten?

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02-11-2021, 01:34 PM	#2
tomm.brz Senior Member Join Date: Jan 2017 Drives: brz 2017 hksv2 Location: italy Posts: 2,195 Thanks: 500 Thanked 1,065 Times in 774 Posts Mentioned: 65 Post(s) Tagged: 0 Thread(s)	disconnecting battery resets like an ecu reflash, LTFT will stay at 0 for a while , and after a bit of driving in closed loop the ecu will start learning LTFT and when it starts it never stops learning and updating the values

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