Custom MAF system: help w/ calculations

[Scot Sealander]

james.drysdale at utoronto.ca wrote:

> I'm implementing a MAF system on the vehicle, and would like to know 
> if I can tap into your expertise (or if you can point me in the right
> direction) regarding the calculation of the pulse width of the fuel 
> injector for a MAF system. There's a lot of good info on the efi332
> website, but it's a speed/density system.

It is just too simple.  The MAF will output a frequency or voltage that
corresponds to airflow.  The ECM will convert that value to gps.  If you 
sample the MAF once per engine cycle, and then divide gps by rps, you
will 
get:

 (grams/sec) / (Revs/sec) = grams/rev

You do 2 revs in an engine cycle.

Convert the mass of air to mass of fuel needed by dividing by AFR.

grams of air/AFR = grams of fuel


To get injector PW, use the injector constant.

grams of fuel * (n sec / gram) to get PW in sec


Then compensate for injector on/off, and inject it.

The real problem is getting a MAF to read the airflow you are going 
to have.  All these values will not be in grams.  Much lower than
that....

Scot Sealander
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org