[Diy_efi] Q regarding placement of a pressure sensor

[Bob Moon]

Hello all,

  I am contemplating the source location for the
airflow signal going to the ECU in my Laser.  It
currently has a Karmann vortex MAF sensor that is
quite restrictive, and expensive to tune (plus, it's
more fun to figure out how to do it myself).  There
are several piggy-back computers that modify the pulse
rate from the sensor to tune the fuel curve, but the
devices that remove the MAF sensor altogether are few
and expensive.

  I am thinking about converting from the MAF to a MAP
sensor arrangement.  Typically, the MAP is routed to
the intake post-throttle body, providing readings from
-15 psi to +30 psi or so.  However, it seems to me
that the mass of the air moving through the system
will be the same before the turbo as after.  

  This leads to my question:  why not run a pressure
xducer before the turbo (say, in the stock MAF
location) and just read the vacuum that is created as
the turbo/engine inhales the air?  This would provide
a reading from -15 to 0 psi (the further negative, the
more air is flowing) reading, and I could then convert
the voltage to a square wave for the ECU to interpret.
 Is this reading not accurate enough?  The only reason
I can see would be that the signal wouldn't be
consistent, but it seems to me that an airflow
consistent enough to make a Karmann meter work would
also provide a consistent, repeatable xducer signal.

Thanks,

Bob Moon

__________________________________________________
Do You Yahoo!?
Yahoo! Autos - Get free new car price quotes
http://autos.yahoo.com

_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi