VE modification calculation, do I have it right?

[Dixit]

Im not sure if there is a confusion on this or is it just in my thick head,

But if the LTFT/STFT histrogram is in percentage, then shouldnt you be doing a calcuation when making the change to the VE table instead of just adding or subtracting?

I see examples of things like:
If your LTFT cell is -5% and your STFT cell is -3% your final learned is -8%. And then you take half of that to avoid overshooting.

Now if you have the VE cell of 60, do you just subtract 4 from it to make it 54 or do you do 60 times 0.96 which then equals = 57.6

Which one is correct?

Dixit

[405HP_Z06]

A negative fuel trim indicates a rich condition and the larger the value in the VE cell the more fuel at that point. So using your example,

(-3) + (-5)= (-8) indicates a rich condition so we want to lower the VE table cell value by half this amount (-4)

VE cell value = 60

(60) x (.96) = 58 if you are using 0 decimal precision

It's easier to select the entire LTFT histogram and use the Paste Special>Multiply by % - Half on the VE table.

Use the LTFT's to get yourself at 10 or less and then turn off LTFT Learning and use only the STFT's to get to +/-5.

[Dixit]

Okay, so its definetely making changes to the table via percentage, not just simple subracting the final learned by half. This makes alot of different in many cases.

So you are saying when the LTFTs are below +/- 10%, just turn off Fuel Trim Learn on the VCM controls when I scan correct?

Also once I get all this inline, do you put the MAF fail freq back to 13500 then rescan and then re-calibrate the MAF, or do you leave the fail freq to 0 and then scan again and then recalibrate the MAF and then put the fail freq back to 13500?

Dixit

[405HP_Z06]

Okay, so its definetely making changes to the table via percentage, not just simple subracting the final learned by half. This makes alot of different in many cases.

So you are saying when the LTFTs are below +/- 10%, just turn off Fuel Trim Learn on the VCM controls when I scan correct?

Also once I get all this inline, do you put the MAF fail freq back to 13500 then rescan and then re-calibrate the MAF, or do you leave the fail freq to 0 and then scan again and then recalibrate the MAF and then put the fail freq back to 13500?

Dixit

You can turn off long term learn through the VCM controls or in the tune through the editor. If you use the VCM controls, you have to turn them off everytime you turn the car off/on. If you turn it off in the tune through the editor they will stay off until you turn them on and reflash.

I logged data to calibrate the MAF table while in SD mode. I made many logs over a few days and used the data to build a MAF table. I then compared them all to make sure all the new MAF table data was similar and I was confident the table was close enough. I then set the MAF fail frequency back to stock, set the low octane table back to stock, turned LT learn back on, entered the new MAF table, and reflashed.

Now reset fuel trims and drive the car long enough for your trims to learn. Log fuel trims and scale your MAF table up or down to bring your trims back to +/- 5. I logged data for RAF at the same time as MAF data to confirm this table was correct also.

[Dixit]

Man I cant thank you enough for helping me through this mess.

When you say scale the MAF table up or down, we talking the entire table by 1-5% or so Until I get the LTFTs between +/-5.

Again thanks for your help.

Dixit

[12secSS]

DO NOT SCALE THE ENTIRE MAF TABLE! Download RedHardSupra's MAF Calibration file, this will help dail in your maf table more precisely. I used it and my trims are no higher than 1 and no lower than -2, I will increase my VE 1% to bring the numbers closer to what I prefer.

http://www.allmod.net/hpt/

[Dixit]

Right but if they are still say over +5 LTFTs, then I need to scale the MAF a bit more dont I? I mean if the VE table is onpoint in SD mode, then when the MAF is connected and it throws it all off, I would need to scale just the areas that changed.

Ive tried the Calibration sheet before and never came close enough to make me happy, but that was before I got the car running in SD mode and the VE table was accurate. So maybe this time it will work right.

Dixit