Do I need an Air Flow Meter?

[Diehl, Jeffrey]

Thanx for your reply.  I have a few more questions, though. <grin>

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.  

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.

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?

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

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
>
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