Air Flow Meter discussion (WAS: "I'm missing something...)

[Bruce]

You wouldn't happen to have it in a different formate would you?.
Bruce

From: "Will Reeve" <will at reeve.org.uk>
Subject: RE: Air Flow Meter discussion (WAS: "I'm missing something...)
> have a look at
> http://www.carlton24v.co.uk/efilist/afmvmap.zip
> Microsoft excel spreadsheet containg part of a data log between the AFM (a
> bosch flap device) and a map sensor on my car. Both signals were
'straight'
> from the sensor. I was investigating it for the inlet tract restriction
> reduction. You can see the pressure waveform on the MAP trace if you zoom
> in!
> Will

> Behalf Of Bruce
> Sent: 17 November 2002 00:25
> To: diy_efi at diy-efi.org
> Subject: Re: Air Flow Meter discussion (WAS: "I'm missing something...)
> Yep, I used to think that too.
> Until someone challenged me with his results.
> Then I data logged both my MAF and installed a MAP.
> It looks to be a tie or the MAF is slightly faster.
> The MAF was a processed output and the MAP was raw data.
> The thermistor in the new GM MAFs is very small.
> Bruce

> From: "Kevin _" <kiggly at hotmail.com>
> > Unfortunately, in the automotive world, all the aforementioned sensors
> > besides the MAP are VERY slow.  From the airflow change to its reported
> > measurement, you have a bare minimum of something like 20ms before all
the
> > corrections are applied.  On the hotwire, the automotive environment
> > requires a very durable sensor, so a big-ole thermistor is usually used
as
> > the hotwire element, which only adds to its latency.  Combine that with
> the
> > air response time of a turbo system that has 2 cubic feet of plumbing
that
> > is being compressed from 1:1 to 3:1 and you're in for some very
> > non-representative readings during spoolup and after you get off the
gas.
> > On the other hand, a general MAP sensor reacts in about 1ms.  This is by
> far
> > the superior way to go for making a drivable EFI setup.  With the
airflow
> > measuring devices, you'd probably have to wait about 4 engine cycles to
be
> > able to calculate an accurate airflow input at 9k rpm (13ms/cycle, total
> > wild guess of 40ms latency), where with the MAP setup you're able to
catch
> > it 1 cycle after the transition.  To take care of the latency issue, you
> > just have to piss fuel in with throttle transition corrections.
> > BTW - I just joined the list earlier today, there seems to be a lot of
> good
> > stuff here!
> > Kevin


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