Closed Loop MAF Calibration (modified approach)

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keridil
Posts: 58
Joined: March 2nd, 2012, 6:05 am
Location: Asturias / Spain

Closed Loop MAF Calibration (modified approach)

Post by keridil »

Hi there,

After some though I tried a different approach to calibrate my MAF, I did read what MAF calibration 101 thread said and I decided to try a easy way or at least more complete way using some Excel functions.

First of all, excuse my English if it sounds a bit funny. Of course, I'll excuse your Spanish! ;)

This is what step 5 of MAF Calibration 101 thread say:
Step 5 – Analyze the Logs

Open the MAF calibration logs in the VersaTuner log viewer. Use the VersaTune MAF Calibration Worksheet attached here to help organize the data and calculate the multipliers to apply to the MAF tables.
Note: At this time, the MAF Calibration worksheet only works in Excel 2007 or newer. I am working on compatibility with previous versions.

Since it is a rather tedious task to record data every .039 MAF volts corresponding to each cell in the MAF Calibration tables, try to record data at least every 3 or 4 cells if possible. Try to get data points from multiple logs to get an average. This will prevent a one-time event from creating a high or low point in your new calibration.

Closed Loop Calibration

At each point in the log where MAF volts and throttle position are steady for a second or more and Actual Equivalence Ratio is the same or very close to the Desired Equivalence Ratio (+/- .010 lambda), add the STFT and LTFT to get the combined fuel trim. Record the combined fuel trim on the calibration spreadsheet next to the corresponding MAF voltage. Do this at as many data points as possible throughout the MAF voltage range where LTFT and STFT are non-zero. The worksheet will calculate the multiplier to apply the cells of the MAF Calibration tables in Tune Editor.
After reading it I went for a drive to the highway, to the town, I did some spirited driving, I did some nanny driving too, all to get a good sample of work loads. I did it a couple of times after letting my ECU learn for 200 km. it is not difficult to me 'cos my commuting distance is 73 km. each day.

I got the logs and I did start working on them.

1) I did import my logs in an Excel sheet, select all the cells and format them to numbers with 3 decimals.

2) Add a new column, we will use this new column to erase every row where Actual equivalent ratio (lambda) and Desired equivalent ratio (lambda) have a difference greater than 0.010. To do that just subtract one from another in the new column, sort the column ascending and select and erase values smaller than -0.010 and bigger than 0.010.

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3) Ok, now you can erase the auxiliary column, not needed anymore. I'll delete Desired and Actual too just for the shake of my convenience. Now, add a new column, we're gonna name it "Distance to MAF V point". In this column we are gonna calculate the difference from our MAF V reading to the MAF V values in VersaTunes Excel. What we are gonna do is calculate the rest of the division of our MAF V reading and 0,039 that is the distance between values en VersaTunes Excel. To do that we will use MOD() function.

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4) In this step we are going to calculate the nearest bottom value of VT Excel for every one of our MAF V readings. In that way we are going to see that we've more than one reading for each point, more on that later. To do it just create a new column, I'm naming it Neartest VT MAF V value (V) and just subtract Distance to VT MAF V values from your MAF V readings and sort ascending for your new column. Create a new column and add LTFTs and STFTs together, name it Combined fuel trim.

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5) Now for the tricky part. As you know by now we got many LTFT+STFT readings for one V reading reflected in VT Excel. We can take advantage of that calculating a average value for them. To do that we are gonna use "Subtotaling" using Combined fuel trim column and Nearest VT MAF V value column. In this case couple of images are better than words.

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After applying just click on top left button labeled "2" and there you got your values to paste in VT Excel. If you have enough probably you can paste chunks of values or even the complete column.

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In your VT Excel you can select all values en VT software and paste then in a column, make another column with the multiplication by your multipliers and copy all new value cells and paste special in a new sheet using the options in this screenshot

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and you can paste it directly en your MAF calibration cells in VT software, take care to avoid first cell because in VT Excel there is no place for 0 value.

If is not quite clear, let me know and I will edit the post any times that is needed.

What do you think Ugnius & Steve, is there any problem with the method?

Cheers.
Mazda 6 MPS, BPV GFB, RX-8 wheels, B8 + Eibach Pro-Kit, CS 3" SRI, GS EBCS (interrupt), CS 3" TMIC, EGR off, HPFP internals, CS catted downpipe, 3 bar MAP, BNRS3, forged engine and stuff
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