i do my own SD tunning but how is MAF tunning done?
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i've never seen any one do it nor do i know what to even search for...
but what is changed when tunning a MAF car that differs from a SD with no o2 feedback....
i hear about PE but im not sure where that is to tune either....
enlighten me a little im sure i'll understand it if i can tune my own stuff with SD im just concerned about doing other peoples cars that have/want there MAF.....
but what is changed when tunning a MAF car that differs from a SD with no o2 feedback....
i hear about PE but im not sure where that is to tune either....
enlighten me a little im sure i'll understand it if i can tune my own stuff with SD im just concerned about doing other peoples cars that have/want there MAF.....
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use the same process that you alter ve to alter maf table.
(ie) If ve is accurate but the tune is out then its maf table fault so apply the relevant corrections to the maf table to make fueling accurate.
apply the corrections iteratively until error is acceptable, first to ve table in sd mode, then to maf table in hybrid factory maf mode.
(ie) If ve is accurate but the tune is out then its maf table fault so apply the relevant corrections to the maf table to make fueling accurate.
apply the corrections iteratively until error is acceptable, first to ve table in sd mode, then to maf table in hybrid factory maf mode.
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In SD mode, Dynamic Airflow is an estimate of airflow that would be measured by the MAF. If you have a good SD tune then the estimate should be fairly accurate. If, with the MAF connected but still running in SD mode, you record Dynamic Airflow and MAF frequency, you will have the information needed to calibrate the MAF. One way to do this is to make an XY graph of Dynamic Airflow versus MAF frequency using Excel. If you then generate a polynomial fit to the data (using Excel's trendline feature), you can use the polynomial to generate a MAF calibration curve. I don't have my notes handy but my recollection is that I used two separate third-order polynomials - one for the low frequency end of the curve, and another for the high end.
Last edited by Gary Z; 08-22-2007 at 05:56 PM.
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Originally Posted by Gary Z
In SD mode, Dynamic Airflow is an estimate of airflow that would be measured by the MAF. If you have a good SD tune then the estimate should be fairly accurate. If, with the MAF connected but still running in SD mode, you record Dynamic Airflow and MAF frequency, you will have the information needed to calibrate the MAF. One way to do this is to make an XY graph of Dynamic Airflow versus MAF frequency using Excel. If you then generate a polynomial fit to the data (using Excel's trendline feature), you can use the polynomial to generate a MAF calibration curve. I don't have my notes handy but my recollection is that I used two separate third-order polynomials - one for the low frequency end of the curve, and another for the high end.
Can one not just log the frequency vs the AFR and adjust the MAF table based on the trends at each frequency column?
I don't understand how you crossreference... Is the airflow based on the VE which you have previously calibrated??
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Originally Posted by 2002_Z28_Six_Speed
Can one not just log the frequency vs the AFR and adjust the MAF table based on the trends at each frequency column?
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GaryZ, you're dead on!
MAF is a 3rd order poly, that's a physical dependency, and as such you cannot dodge it. I do not agree with using AFR%error based adjustments to the stock curve as that ruins the shape of the polycurve.
the way it should be done we should use airflow estimates created from fuel and AFR measurements
airflow=cylinders*cylinder airmass*rpm/120
where
cylinderairmass= IPW*IFR*AFRwb
and then chart it against MAFhz, and fit the 3rd order poly to this function, hopefully also removing the obvious outliers. this method is highly dependent on how realistic your IFR figures are, and how well your wideband is calibrated, that's good data cleanup and robust fitting techniques are highly recommended.
MAF is a 3rd order poly, that's a physical dependency, and as such you cannot dodge it. I do not agree with using AFR%error based adjustments to the stock curve as that ruins the shape of the polycurve.
the way it should be done we should use airflow estimates created from fuel and AFR measurements
airflow=cylinders*cylinder airmass*rpm/120
where
cylinderairmass= IPW*IFR*AFRwb
and then chart it against MAFhz, and fit the 3rd order poly to this function, hopefully also removing the obvious outliers. this method is highly dependent on how realistic your IFR figures are, and how well your wideband is calibrated, that's good data cleanup and robust fitting techniques are highly recommended.