Do I need an Air Flow Meter?

[Bruce Plecan]

> You mention that I would probably need a sensor for barometric  pressure,
> air temp, and RPM.  The stock AirFlow Meter doesn't have any of this.

Doesn't have to, it's figuring mass

> I can see how one might argue that the difference between the engine vac
and
> the barametric pressure is what the AFM is measuring, so if this is
correct,
> I can see why I'd need the two pressure sensors.

Just too hard in my opion to get enough resolution in using just a MAP to do
it.
Hard to tell at times if your actually doing what ya seem to be doing
because of Baro.

> I can see where it would be NICE to know air temp, but my ECU doesn't seem
> to use it.  In lue of that, couldn't I just rely on the Ox sensor to
adjust
> fuel correctly?

If all you want is to run 14.7:1, or go for a wide band.

> Would simply tying a potentiometer (sp?) to the throttle linkage be enough
> to replace the AFM?

If all you want is a Alpha-N system..
Meaning figure AFR on throttle opening, and rpm.
Yes you can do that, and if that is all you use it will be border line to
even be able to drive some days.
there is a too min system that is too min
Bruce

>
> Otherwise, would I need a circuit much more complex than a MAF and an
OPamp?
>
> Thanx again,
> Mike Diehl.
>
> -----Original Message-----
> From: Bruce Plecan
> To: diy_efi at diy-efi.org
> Sent: 11/11/00 12:49 PM
> Subject: Re: Do I need an Air Flow Meter?
>
>
> IMO
>
> one map sensor for barometric presure
> one for engine vac
> intake air temp
> RPM
> Should be enough for a substitute AFM
> Or use a late GM MAF and just do a freg., to what ever output your AFM
> uses
> Bruce
>
>
>
>
> > Hi all,
> >
> >   I'm in the process of putting an engine in my car, an '87 MR-2.
> I've
> looked at the AFM, a flapper door type,
> >   and decided that it is very restrictive.  I'm contemplating building
> a
> circuit that looks like an AFM to the
> >   computer.  I will link this circuit to the throttle linkage.  I know
> that the computer needs this information, but
> >   isn't it using it to measure how much load is on the engine, ie.
> More
> load = more vacuume = more open AFM
> >   door?  Instead of the computer determining load, the driver will
> determine it by how much he presses the
> >   petal.  Think of it as a variable substitution into the fuel
> equation.
> >
> >   If that wont work, how about this.  Then I get a MAP sensor and make
> an
> op-amp circuit which maps the
> >   outputs appropriately.  A MAP is a lot less restrictive than an AFM.
> >
> >   Since the car isn't running yet, I've had a lot of time  (too much?)
> to
> think about things like this.  I've also had
> >   the oportunity to learn about just about ever major system in it.
> The
> car is a project car, so when it is running,
> >   I can do whatever modifications I care to do.  That is, it's not my
> daily driver.
> >
> >   Look forward to your comments.
> >
> >   Mike Diehl
> >
> > Mike Diehl
> > 87NA 7afe, dual exhaust & custom headers
> > ---------------------------------------------------
> > Get free personalized email at http://www.iname.com
> >
> ------------------------------------------------------------------------
> --
> --
> > 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
> >
> >
>
> ------------------------------------------------------------------------
> ----
> 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
>
>
>

----------------------------------------------------------------------------
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