Hi Dave,

Wow, you've brought back some memories from a "previous life"...  boxes with
hundreds of Weber carb jets, calibrated accelerator pump nozzles, etc.
...And fixing the calibration of previously "adjusted" Bosch air flow meters
on my Clayton dyno -- heh, heh.

If you haven't settled on a MAF yet, you might want to take a look at those
made by Mitsubishi.  They output a nice 5V digital signal with frequency
based on air flow.  The sensitivity is great; at idle you can actually see
each cylinder taking its gulp of air -- with enough resolution to spot a
cylinder that isn't pumping properly.  Watching that signal along with a
hi-res manifold vacuum waveform (from a good MAP sensor), and the O2 sensor
signal, opens up some interesting diagnostic possibilities.

Does your engine have a throttle position sensor (pot)?  Typically rapid
changes in TPS signal value are used to provide the "accelerator pump"
function on modern engine management systems.  This provides considerably
faster response than waiting for the MAF to respond, which can easily be
verified by dual-tracing the signals on a DSO.  (Ever notice how those early
Bosh vane air flow meter systems just didn't have the crisp throttle
response of a nicely set up carb system?  Part of that was calibration for
emissions, though.)

I have several new Mits MAFs used on a current 2.4L engine that I obtained
for a "one of these days" project.  We'll see if that ever happens  :o)

Randy
www.glitchbuster.com


> Background: I've got a car which uses a simple Vane airflow meter, which
> consists of a spring loaded flap, of which the engine airflow pulls open
> to varying degrees. I wish to use a mass airflow meter as its
> replacement, due to its lack of moving parts and larger flow.
>
> The problem: the vane airflow meter was designed to have a certain
> amount of overshoot, to act as an 'accelerator pump' in carby terms, as
> acceleration enrichment.
>
> I wish to create a pic-based board that simulates the effect of a loaded
> spring. Is there anyone with a natural gift at physics formulas etc that
> would be willing to assist me in the design of such a simulation?
>
> I intend to post the design up on a page when I'm finished, so I am not
> looking to make a profit off it at all.
>
> Thanks,
>
> Dave
>
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