Mass airflow sensors.

[Buchholz, Steven]

Well, it seems to me that you could hook the MAP sensor up to your car and
hook up a data collection system that included information about the "VAF",
MAF and tach inputs which should give you the necessary transfer functions.
Once this info was available it should be a simple matter to create a
computer that would take the MAF and tach inputs and output the simulated
VAF.  AAMOF, one could design a computer that "learns" the transfer
functions by accepting the VAF, MAF and RPM inputs in a learn mode.  This is
probably why Link is tight lipped about what they do.  

The thing that makes me wonder why you would even want to do this is that
the ECU to which the VAF is attached is calibrated to the characteristics of
the VAF.  It is expecting that small signal change for a given change in
flow at high rates.  What do you expect to accomplish with this mod?  Please
don't take this message as being a flame ... I'm working with limited
information here ... I don't even know what kind of car we are discussing
here.  If you were talking about reprogramming the maps in the ECU then this
sort of swap might make a lot more sense ... and might make it possible to
simplify things.  Many ECUs already have an independent RPM input that
becomes one of the input variables to the fuel/timing maps.  If you know how
the inputs are processed to access the maps it seems to me that it should be
completely possible to hook the MAP sensor directly to the input to the ECU
and account for the differences in the behavior of the two signals by simply
programming the map appropriately.  You will probably still need to do some
experimentation to determine the different behavior of the VAF vs MAP
sensors.  

Good luck with your project!
Steve Buchholz
San Jose, CA (USA)

> -----Original Message-----
> 
> I am looking at how to replace my car's stock airflow sensor (a VAF, or
vane
> airflow sensor) with some other kind.  I've worked out most of the logic
> changes that are required in the ECU.  The main reason for doing this is
the
> highly non-linear nature of the VAF's output -- at high airflow rates the
> device saturates and large airflow changes results in tiny 
> voltage changes.
> 
> One possibility is a device made by Link Technologies called the Link AFM.
> It is a computer with a MAP sensor and an RPM interface that generates a
> voltage signal that can be hooked to the stock ECU's airflow input.  It is
> programmable, allowing extensive tuning.  Its also expensive, and Link
won't
> part with an information about the shape of its output curve.
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