FW: MAF Upgrad

[jb24 at chrysler.com]

Be careful about mounting the whole shebang in a larger tube.  The
newer Bosch hot-film units are just probes that plug into a tube - just
screw into a larger housing and voila.  The hot-wire type are
integrated into the housing wouldn't give the same flow characteristics
if stuck into a bigger bore.
---------------------- Forwarded by John R Bucknell/JTE/Chrysler on
02/25/98 09:07 AM ---------------------------

        owner-diy_efi @ efi332.eng.ohio-state.edu
        02/24/98 06:52 PM
Please respond to diy_efi at efi332.eng.ohio-state.edu @ SMTP
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cc:
Subject: Re: FW: MAF Upgrad

No, the idea Mr. Mathews and I had (it's nice to know other  people are
as deranged
as yourself!) was to mount the MAF sensor INSIDE a larger tube.  Don't
touch the
original housing.  Just let the air flow through and around the
original housing.
My first assumption was the MAF ECU's used look up tables like the MAF
computers.
If this isn't so, then the changing of the eprom data maybe more
difficult than a
MAP ECU.

Fluid mechanics was my weakest subject.  Part of the reason was nothing
about
compressible flow is linear if the flow and pressure ranges are very
wide.  In other
words I haven't a clue about the linearity of the flow vs. the MAF
area.  Part of
the problem is the percentage of the air flow through or around the MAF
could change
from idle to full throttle.  It would be a fun problem to figure out.

Joe Boucher
'70 RS/SS Camaro  '81 TBI Suburban

lkurek at smtpgate.anl.gov wrote:

>      The GM MAF is a Bosch unit.
>
>      So, you say I can cut away the 3" tube and replace it with a 4"
one,
>      which would result in a 78% increase in flow area and compensate
with
>      an increase in fuel pressure and/or injector size, in order to
use the
>      same fuel map in the ECM? (I know...I could get a programmable
unit,
>      but hey...I'm trying to be creative here :) ).
>
>      So, assuming my current fuel map was set with 22lb/hr injectors
>      @43psi, I could bump my fuel pressure to 76psi (please bare with
>      me...I know I could get into an injector lock problem here), or
go to
>      40lb injectors (or a combination of both), and this would
correlate
>      with the decreased MAF input to the ECM?
>
>      Anything else? What about low speed resolution? What about
setting a
>      code for inadequate GPS flow at a given RPM? How linear is the
flow
>      rate to MAF area?
>
>      TTYL!
>
>      Larry
>