Barometric pressure

[lance]

'93 to '98 Toyota Supra turbos for all 50 states have a barometric sensor
inside the ECM.  Just another reason I'd like to be able to crack into one
and disassemble the code.

Lance Wolrab

-----Original Message-----
From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
Behalf Of Jason Haines
Sent: Thursday, September 13, 2001 10:09
To: diy_efi at diy-efi.org
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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