[Diy_efi] Re: Q regarding placement of a pressure sensor

[Bob Moon]

Thanks for the info.  

I understand that MAP and MAF are completely
different, but I am not attempting to just replace the
MAF with a MAP and call it a day.  I'm attempting to
map the MAF signal to the voltage output of the MAP so
I can use a uC to simulate the output of the MAF
(square pulse wave, rather than a voltage).  That way,
my ECU will still think it has a MAP.  

Since I am only interested in the amount of air
flowing through the engine at that point in time, my
question is this: for a given airflow count from a
MAF, is there a given vac in the intake?  It seems to
me that a given airflow will always have the same
pressure signal, regardless of what's happening
downstream of the turbo.

I know this is all possible thanks to the existence of
various conversion kits (TRE's MASC and the VPC, for
examples of two voltage-to-frequency converters).  I
just don't know for sure where in the airstream I
should place the MAP tap to get the most reliable and
consistent readings.

Thanks again,

Bob Moon
'92 Laser RS AWD

> Date: Mon, 15 Jul 2002 13:22:53 -0500
> From: steve ravet <sravet at arm.com>
> To: diy_efi at diy-efi.org
> Subject: Re: [Diy_efi] Q regarding placement of a
> pressure sensor
> Reply-To: diy_efi at diy-efi.org
> 
> Bob Moon wrote:
> >   I am thinking about converting from the MAF to a
> MAP
> > sensor arrangement.  Typically, the MAP is routed
> to
> 
> You can't replace a MAF with just a MAP.  You need
> some estimation of VE
> in order to calculate MAF from MAP.  GM ECMs use a
> table indexed with
> both MAP and RPM.  You could also use throttle
> position plus MAP (less
> accurate).
> 
> --steve
> 
> 
> -- 
> Steve Ravet
> steve.ravet at arm.com
> ARM,Inc.
> www.arm.com


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