Disassembly: MAF tables and Air Flow Calculation

[Greg E]

Sorry I missed this question.

What are the cell contents in the fuel map? Is it a straight injector pulsewidth or is there postprocessing?

The only tables which uses straight IPW are the startup tables and the Alpha-N fuel map (limp mode).

There's quite a bit of code after the fuel table look up before it gets processed with the IPW calculation. The next sub deals with knock enrichment, lean spool enleanment and closed loop modifiers. Things like warmup enrichment, accel enrichment, decel enleanment... All that is taken care of large IPW calculation subroutine.

[DG]

So I'm finally working on this.

I have this:

Load_OBD2 = (MAF Pulses Per Second/RPM) * MAF_Size * BaroComp * AITComp / 65536

For simplicity's sake, assume BaroComp and AITComp are 1 (legit if tables have same slope and same X intercept)

I'm bashing my head on the units... it's like I can't do friggin' algebra any more. Out of practice... But using Google's calculator (which does units!) and a bunch of scribbled-on paper, I came up with something that seemed reasonable, but was off by a factor of 2.

GregE, I need your help to sanity-check my work, and confirm that it is crank revs that are being used as the MAF count window, not cam revs.

What I need to make the AEM side of the equation is a number of pulses per rev that equates to a given load value.

So for example, those timing "big maps" span 10 g/s to 320 g/s. What is the equation to turn "320 g/s" into "n pulses/rev"?

Not pulses per second - pulses per REV.

Thanks,

DG

[Greg E]

It is CRANK revolutions being used, not cam. Pulses per stroke goes off the crank sensor.

Edit: let me get back to you on the g/rev conversion. Petty sure that g/s number is actually grams/stroke (or grams per rev however you want to word it).