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MAF constant 1010048999...
Posted: Mon Sep 25, 2017 9:32 pm
by ol boy
What does this number 1010048999 represent? Ive played with the known unit conversions and cant seem to get anything close. 2.54^3 x 1728 x 3600 is a 10x short. Maybe adding lbs/hr to ml/min.. I dont know. That cancels out the 3600 in one form or another. In the MAF math this constant get divided by engine displacement then by airdensity.
Just trying to wrap my brain around the MAF math.
Thanks Ryan
Re: MAF constant 1010048999...
Posted: Mon Sep 25, 2017 9:38 pm
by whittlebeast
Re: MAF constant 1010048999...
Posted: Mon Sep 25, 2017 9:42 pm
by ol boy
Yep, thats where i got that big number from. Something to do with cc.. Uhm.
Re: MAF constant 1010048999...
Posted: Wed Sep 27, 2017 3:45 pm
by robs
Not an area I've looked at, but the code has this to say:
Code: Select all
/* was 61840750 for CID */
/* this factor is calculated as follows - only used to generate mafload
by definition mafload = 101.35 kPa at 100% VE = 1013.5 units.
Density of air at 20C and 101.35kPa = 1.2041 x 10^-3 g/cc
airden factor = 100.0% at 20C = 1000 units
mafload = ((MAFCoef / aircor) * maf) / rpm)
at 100% VE, flow = size x rpm/120 x 1.2041 x 10^-3 x 100
maf = 100 x flow units
The 120 is converting from rpm to cycles/sec on a 4 stroke
MAFCoef = k / size
So, 1013.5 = ((k/size / 1000) x 100 x flow) / rpm
or k = 1.0135 x 10^6 x size x rpm x 120
---------------------------------
100 x size x rpm x 1.2041 x 10^-3
rpm, size drop out
k = 1.0135 x 10^6 x 120 / (100 x 1.2041 x 10^-3)
= 1010048999
(not quite the same as Al's figure 1013569893L which appears to use air density as 1.200x10^-3
*/
which seems to explain it pretty well.
Have fun,
Rob.
Re: MAF constant 1010048999...
Posted: Wed Sep 27, 2017 6:57 pm
by ol boy
Which file is that in? I looked through the msextra main.h
Re: MAF constant 1010048999...
Posted: Wed Sep 27, 2017 9:23 pm
by robs
It's in ms2_extra_init.c
Easily turned up with "grep 1010048999 *.[ch]" in Linux, or in Cygwin under Windows.
Have fun,
Rob.