Mass airflow sensors.

[nacelp]

Just some numbers to mull over while your thinking this thru.
Joe Average driver thinks .1sec is an instanteous response.  The best of F1,
can detect .01 (I think it was Senna, that set this "record").   This is
just in reference to engine response.
The 200 msec., might be to fully stabilize, on the hot style sensors but a
good part of that is smoothing to a level you'll never notice/see.  The
transistional delay to airflow is several msec., as I've heard reported.
  There is no AE (or little, to none), on the gm MAFs, yet on the MAPs there
is MAP AE, Coolant temp AE and TPS AE.  (AE=Accleration Enrichment).
  If your system is looking for a V difference, how does the Ford MAFs line
up?.
Can you get a Ford sensor and put it in parrarell with your door sytle
sensor and compare them, and then use your existing code (with changes) to
"read" the other sensor?

> Hmmm... this is a strong argument for converting to speed/density.  The
> pressure change should be instantaneous -- or at least as fast as the VAF
> signal change.  Another issue that has been brought up is that a MAF might
> not work well in a boosted situation like mine... it might not be pressure
> tight and will get dirty quickly if downstream from the turbo.  I don't
have
> room to put it upstream.
>
> These factors make the LinkAFM look more appealing again.  My theory on
the
> Link is that they built it to replace MAFs or flapper-door style VAFs, so
> they will have attempted to generate a signal that is reasonably
compatible
> with a MAFs output.  This gives me a baseline to start with, and tune on
the
> dyno from there.  I suppose it doesn't hurt to ask:  does anyone have the
> output plots from a conventional flapper door style VAF?
>
> Somebody else pointed me to the HKS Vein Pressure Converter, which acts in
a
> similar manner to the LinkAFM.  It is considerably more expensive, and
LESS
> easily programmable, however.  Anyone know of any other options?
>
> Thanks for bringing up this issue, I had been concerned about response
times
> but had heard/seen no mention of it anywhere.
>
> Cheers,
>   Andrew
>
>
> ----------
> >From: "nacelp" <nacelp at bright.net>
> >To: <diy_efi at diy-efi.org>
> >Subject: Re: Mass airflow sensors.
> >Date: Sat, Feb 19, 2000, 5:02 AM
> >
>
> > How about adding a MAP sensor, and looking for a sudden change in that?.
> > Grumpy
> >
> >
> >> Hi,
> >> I'm also working on converting my AFM to MAF but I've ran into a
> >> couple problems that I don't see mentioned here.  The response
> >> time of the AFM to changes in air flow is almost instantaneous.
> >> However, the MAF (GM hot film sensor) requires about 200ms to
> >> fully react to a change in flow.  If I map the MAF signal to an
> >> equivalent AFM voltage, the car runs great, as long as I don't stab
> >> the gas.  If I do, I basically go very lean for 200ms resulting in a
> >> very nasty head jerking event.  My thought was to use the
> >> derivative of the TPS signal to compensate during the 200ms.
> >> Unfortunately, my car doesn't have a TPS.  If there any way to
> >> accomplish what I want or do I have to add a TPS?
> >>
> >> Any thoughts?  BTW the car is an 88 BMW 535i if that helps.
> >>
> >> Thanks.
> >>
> >> Brian Franchuk
>
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