[Gmecm] Re: MAF specs and MAP replacement.

[Robert Fleming]

n is number of moles, not mass

and tpi and ford 5.0 setups don't have a map sensor if
they are mass air.  Thats a new thing, 93 or so.

Robert


--- Steve Ravet <Steve.Ravet at arm.com> wrote:

> The end goal of EFI is to inject the correct amount
> of fuel for the mass
> of air that is passing through the engine, to
> produce the desired
> air-fuel ratio.  So knowing the mass of air passing
> through the engine
> is the crucial bit of information.
>  
> MAF measures mass directly.  If you don't have MAF
> then you have to
> calculate mass.  Look up the ideal gas law, PV=nRT.
>  
> P=pressure
> V=volume
> n=mass
> T=temperature
> R=constant to make units work out correctly.
>  
> MAP gives you pressure.  Volume is calculated from
> RPM.  T comes from
> the inlet air temp sensor, or is just a constant. 
> This calculation is
> generally done beforehand and stored in the form of
> a volumetric
> efficiency table that is indexed via MAP and RPM.
>  
> So your box will have to take MAP and RPM as a
> minimum, and will have to
> have some constants related to the engine in there
> also.  What's your
> application?  I think most MAF systems fall back on
> MAP in the case of a
> defective MAF sensor, you can probably "convert" to
> MAP by simply
> unplugging the MAF.
>  
> --steve