Thread: MAF Calculations

The documentation states:
MAF Load is calculated by multiplying MAF LOAD FACTOR times Q from MAF VQ Table and dividing by RPM. MAF load scale values are MAF Load divided by 256.

So... I'm attempting to run these calcs myself with logged data.

Does "MAF load scale values" refer to the value that is used to look up the fuel/ignition cell values? If so, my calcs aren't matching what's being reported/used.

Let's start this off simple. Does Q get pulled from the closest voltage (in the VQ table) up or down?

My Values:
MAF Load Factor: 2714
MAF Voltage: 1.79
Q(N62): 2397 or 2095
RPM: 1738

If up:
MAF Load = 2714 * 2397 / 1738 = 3743
Load Scale = 3743 / 256 = 14.62

MAF Load in the log is 41... What am I missing here?

The ECU uses different units so the numbers will not come out equal. The doc says "is calculated by" which does not mean "is equal to" in this case. The equation is correct and tells you how MAF load is calculated so you know how it changes proportionately with MAF voltage and RPM.

What different units does the ECU use? If I'm not mistaken, the RT version actually showed what the MAF Load value was...

SA logs the MAF Load too. What problem are you having that you're trying to solve?

The SA shows the MAF load value that you are using.. it is the third item in the data screen.

There is a pretty big difference with how the maf load factor is used in the SA version compared to the RT version.

If you notice, the MAF load factor is MUCH lower than the K-value from the RT version.

What exactly are you trying to accomplish in doing the calculation yourself? Just for a better understanding?

Pretty much... I'm trying to show mathematically how the fuel cell value, MAF (or map when I switch to it) load and rpm affects my AFR under various conditions... TPS, ECT, Accel/Decel, etc.

Ultimately, I would like to be able to determine the factor responsible for a variance in the IPW and resulting AFR...

All of the factors that determine IPW, and how their weight is applied, are given in the doc. The correlation to AFR will have to be done empirically.

Yes, and John has informed me that accel/decel item values will be added to the log shortly.

Is there any way to calculate the throttle open/close rate based on logged values?

The "dTPS RATE FACTOR TABLE" index can be logged which would allow that table to be traced.