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

[Diehl, Jeffrey]

What format would you like it in?  I can convert to just about anything.

Lemme know,
Mike Diehl,
'87 MR-2, 7age, Dual Pipes, hand-bent header.
'96 4-Runner, Bone stock.
'90 Corolla, Disguised as a Geo Prism!


> -----Original Message-----
> From: Bruce [mailto:nacelp at bright.net]
> Sent: November 18, 2000 1:55 PM
> To: diy_efi at diy-efi.org
> Subject: Re: Air Flow Meter discussion (WAS: "I'm missing 
> something...)
> 
> 
> 
> 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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