MAF Calibration 101

VersaTuner for Mazdaspeed6, Mazda 6 MPS, Mazdaspeed3, Mazda 3 MPS, CX7
Kay2thePea
Posts: 12
Joined: May 28th, 2025, 10:58 pm

Re: MAF Calibration 101

Post by Kay2thePea »

mituc wrote: July 1st, 2025, 7:37 am
Kay2thePea wrote: July 1st, 2025, 7:05 am two things i'm confused about here:
Honestly the way you ask these questions makes them impossible to answer. So what you can do is to find your MAF calibration in the "Share your MAFcal" thread.
i'm really sorry. i'm autistic, and i don't always communicate in the best way for others to understand. my struggle is that i honestly don't understand what the issue is with the way i ask my questions, because to me it is exactly how i think and i follow it fine. but i of course would much rather ask in a way that makes sense to everyone else, so i can get help instead of just coming off as rude or ignorant or whatever (I have been told plenty of times that's how i come across sometimes, not saying you are suggesting it, just accepting/admitting that it's something i've been told in the past by others).

how could i ask better questions, or how could i improve them?

in this case, i feel like my first question is pretty clear yea? this one really might be my autistic way of taking things very literally. the worksheet says "open loop" on it, and there isn't a separate worksheet in the file that says "closed loop", so to me it feels like maybe the wrong file was uploaded and there is another version that has two worksheets, or that the title of the sheet doesn't matter and that the same exact sheet is used for both open and closed loop. i'm guessing that it's the second option?

for my second question, i'm just wanting to confirm that we shouldn't expect LTFT's to go to zero or near zero after any amount of driving (without changing MAF calibration numbers at least)? I asked this because of the way it was worded in the original post here where steve said that they will go to zero and at that point we know that the car has learned fuel trims and the MAF calibration logging session can be done. So it made me wonder "is it possible that the ECU actually commits LTFT's to the fuel maps themselves by modifying the fuel maps, such that the LTFT's will actually drop to near zero or zero over time?" I'm not super familiar with how fuel mapping and how ECU's actually control and run the engine, not in detail for sure. I have a really good grasp on physics and chemistry, and i can usually teach myself/learn things when i want to, which is what i decided i wanted to do wrt ECU tuning on my car. But because I'm really still learning, i end up with questions like this that might seem kinda dumb. sorry if that's the case. I just really want to make sure i'm not screwing shit up, and since i know i sometimes take things more literally than i should, i try to ask questions to make sure i am understanding shit clearly.

as for my last question.... i can see how that was a confusing question. I guess what i really would love is to have a way to really understand exactly how the ECU decides what table it is going to use at any given moment. But it seems like there isn't really a complete guide that gets technical enough to explain these kinds of things?

thanks for taking the time to respond to me, and i appreciate any help you offer me and appreciate your patience with me and my questions. i'll try to be more clear about them. thanks again man!
mituc
VersaTuner guru
Posts: 1447
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: MAF Calibration 101

Post by mituc »

Kay2thePea wrote: July 2nd, 2025, 3:09 am i'm just wanting to confirm that we shouldn't expect LTFT's to go to zero or near zero after any amount of driving (without changing MAF calibration numbers at least)?
Indeed, the fuel trims, both short and long term, are a measure of the momentary fuel correction applied by the ECU. If you manage to get the fuel trims 0 in some weather/humidity/barometric pressure/temperature conditions, most likely they will not be 0 any more 2 hours later when the weather will get hotter or cooler. That is what these fuel trims do, they show how much the ECU corrects for fueling. These corrections have their roots on how the MAF sensors work, and by how they work they measure volume rather than mass, and the fueling needs to estimate mass.
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Therefore it's not a problem to have non-zero fuel trims, it's absolutely normal/natural. What's not normal is to have the fuel trims vary too much, either because of an improper MAF calibration or a defect (leak). Aiming for 0 fuel trims is like aiming for the same heartbeat when you're both running or sleeping, it's simply not possible.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~550BHP @35PSI
2008 Icy Blue Mazda CX7
Built engine and stock exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 360-ish BHP
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