Monday, May 02, 2005

Logging for MAF calibration made easy

Apparently if you just want to adjust your MAF calibration you do not need to get into Speed Density mode! A guy named Drew approached me on the HPTuners board, asking why we need to go to SD for MAF calibration. I never really questioned this procedure, as usually I do both at the same time (as new MAF will need a new VE) so I must have it in Speed Density anyway.

So I told Drew to do a little experiement, do few logs in SD and then another few in MAF. We compared the results, and they were nearly identical, any differences were mostly based on not having enough samples. The more samples for given calibration point we had, the closer the two calibrations got.

The good part of this is that you can grab any number of data you got, any mode too, and just keep using the historical compounding function of my spreadsheet to get large numbers of samples, creating a truly universal calibration.

This little fact gets rid of the most annoying fact: you never seem to have enough data for the higher frequencies, as it's hard to get on the gas that long without getting into some hairy situations. But over a course of few days or weeks of more casual data gathering, with an occasional WOT run here and there, you will eventually get enough data. How much is enough? I'm satisfied with my data once I go over 100 samples for each interval. 100 samples at higher frequencies especially, create some very little discrepancies as far as the calibration is concerned. At lower frequencies, I guess since there is more 'leeway' for the air to move in, they still differ, but you end up with so much data for these (because you get it just sitting at stoplights and getting groceries), that the calibrations come out within just few percent of each other.

Hope that speeds up the process. I just spliced a bunch of data files I've had after my last volumetric efficiency altering modification (LS6 intake) and now I have thousands of samples for each calibration point, hopefully yielding a true calibration of my Granatelli MAF.


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