Confused about MAF

[joecar]

Also look at post #29 here: Summary-Notes

it explains the difference between Calc.VET and Calc.MAFT

( note how "calculated" and "corrected" are used )

[joecar]

So your LM1 is programmed like an LC1 (0V = AFR 7.35 and 5V = AFR 22.35)...?

Edit: I see that it is.

[wcj]

So your LM1 is programmed like an LC1 (0V = AFR 7.35 and 5V = AFR 22.35)...?

Yeah, that's the best I could find for the analog LM-1.

Btw, thanks for looking at all this for me.

[joecar]

if you're doing Calc.VET (which corrects MAF and calculates VE from it):

[ running with VE disabled via B0120 (altho the transient filter removes VE influence) ]


corrected MAF:



calculated VE:

[wcj]

So since my MAF is not disabled, the data from the posted Calc.MAFT would be horribly skewed due the the MAF, correct?

[joecar]

if you're doing Calc.MAFT (which corrects VE and calculates MAF from it):

[ running with MAF disabled via C2901,3 ]

corrected VE:



calculated MAF:

[joecar]

During steady state, the MAF is the source of airmass.

During transients, above B0120 the MAF is the source, and below B0120 the VE is the source.


So during Calc.VET, if you filter out transients below 4000 rpm (stock value of B0120), you are filtering out the VE contribution... but you shouldn't rely on this (how can you be 100% certain that you filtered out all the VE contribution). It is safer to edit B0120 to disable the VE, but see post #20 below.


During Calc.MAFT, there is no way to filter out the MAF contribution because when you filter out transients you're removing the VE contribution and keeping the MAF contribution. It is necessary to edit C2901,3 to disable the MAF.

[joecar]

Easy way to remember all of this:


whatever thing is being calculated (the name of the method) has to be disabled...

and the other thing has to be corrected so it has to be enabled.

[joecar]

Calc.MAFT: corrected VE (enabled) -> calculated MAF (disabled)

Calc.VET: corrected MAF (enabled) -> calculated VE (disabled)

[joecar]

So since my MAF is not disabled, the data from the posted Calc.MAFT would be horribly skewed due the the MAF, correct?

If the MAF is enabled it is contributing to the airmass computation rather than the VE... the correction BEN factor is the error fraction in the source of the airmass (MAF if it is enabled).


Since Calc.MAFT is using corrected VE to calculate the MAF, it misses its point.


Of course, if the VE and MAF are already sufficiently close then you won't see any significant difference.