Barometric pressure

[Bruce]

There are several strategies.
Some take a glance at startup, then others at 3/4 throttle, do a review of
it
The earlier ones use a full time baro sensor.
(the above, reference GM)
Bruce


----- Original Message -----
From: "Programmer" <nwester at eidnet.org>
To: <diy_efi at diy-efi.org>
Sent: Friday, September 14, 2001 10:04 AM
Subject: Re: Barometric pressure


> I never knew the Baro value changed...until next key on. One reason is
that
> you can start an EFI down here, drive to Banff--and it's running on the
rich
> side till you stop for gas <G>... suddenly, it's fixed. The 3000 ft
> elevation change isn't updated till next key on cycle. If they're using a
> WOT run for an update, I dunno--IMO it's not the whizziest idea in the
park.
>
> Lyndon.
> ----- Original Message -----
> From: "Jason Haines" <jhaines at lingenfelter.com>
> To: <diy_efi at diy-efi.org>
> Sent: Thursday, September 13, 2001 11:08 AM
> Subject: Re: Barometric pressure
>
>
> > On the newer GM vehicles, (such as the 1994 application originally asked
> > about) the MAP sensor is used to determine the barometric pressure. In
> > addition to setting the barometer to the MAP reading at key up, the MAP
> > readings are also compared to the stored barometer reading under
different
> > conditions (WOT being one of them) and changed based on the expected
> > pressure drop in the system at different RPM levels, throttle positions
> and
> > air flows (in MAF based systems). Different vehicles, ECMs etc. have
> > different levels of complexity of this model.  It is my understanding
that
> > one of the reasons for doing this form of barometric pressure updating,
in
> > addition to whatever issues the OE may have, is to comply with EPA and
> CARB
> > requirements for altitude compensation (manufacturers are no longer
> allowed
> > to have separate high altitude calibrations).
> >
> > Some appilications do use a separate barometric pressure sensor but this
> is
> > rare (I only know of one GM application).
> >
> > The above information applies to GM vehicles but should be true for many
> > other applications. They all want to save money on sensors so they try
to
> > reduce the content on the ECM and in the vehicle (plus, less parts means
> > less parts to go bad).
> >
> > Just my $0.02
> >
> > Jason
> >
> >
> > > As far as I know--it's only a snapshot at key on.
> > > I don't know how it'd do it at WOT...if exhaust was
> > > partially plugged, it'd really wonk the settings.
> > >
> > > Lyndon.
> > > ----- Original Message -----
> > > From: "terryk" <terryk at foothill.net>
> > > To: <diy_efi at diy-efi.org>
> > > Sent: Wednesday, September 12, 2001 7:00 PM
> > > Subject: Re: Barometric pressure
> > >
> > >
> > > > Correct me if I'm wrong, but doesn't some early code measure it at
> WOT?
> > > >
> > > > TK
> > > >
> > > > ----- Original Message -----
> > > > From: "Programmer" <nwester at eidnet.org>
> > > > To: <diy_efi at diy-efi.org>
> > > > Sent: Wednesday, September 12, 2001 5:17 PM
> > > > Subject: Re: Barometric pressure
> > > >
> > > >
> > > > > The MAP sensor (at key on).
> > > > >
> > > > > Lyndon.
> > > > > ----- Original Message -----
> > > > > From: "bob r johnson" <bobj_johnson at juno.com>
> > > > > To: <diy_efi at diy-efi.org>
> > > > > Sent: Wednesday, September 12, 2001 7:03 PM
> > > > > Subject: Barometric pressure
> > > > >
> > > > >
> > > > > > Could someone tell me, on a 94 Z28, what sensor measures
> barometric
> > > > > > pressure?
> > > > > > Thanks,
> > >
> >
>
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