Programming 101

Bruce Plecan nacelp at bright.net
Sun Oct 11 15:24:54 GMT 1998


  If your just now tuning in, please go to the DIY_EFI site, and read
all the related 101 material.
Again, this is for the gm 1227747 ecm.
  The IAC is used in a number of ways.  It's range can be from
like 150, to 0.  At the higher counts means it's bypassing more air,
past the throttle butterflies.
  A cold engine start beings with turning off the engine.  When the
engine is turned off, the IAC resets to a given number of counts in
preparation for the next start.  A very common number of steps/
counts for the 747 is 145.
  If you read thru, the switches, table, settings part of the prom, you'll
find some 145 entries (91h) {a total of 4 locations in the ones I looked
at}.
  05DE seems to be a high limit warm engine,
  05C2 seems to be the cold start max setting.
  These numbers are alot more critical then they might appear.
Since they also, interact with the Crank/Prime fuel.  Too low of IAC will
make for a very rich initial, unless the crank fuel is lessened.  But,
the engine does need x amount of fuel as a prime to start.  X will
change as the engine wears, as a function of coolant temp, and
air temp..
  Also, there is no mention about the VSS relationship, or anti-stall
strategies mentioned.

If you want to use a 747 on your Audi the first thing to change is the
cylinder select at 0016.  It understands 8 for 8 cylinder, 6 for 6 cyl,
and seemingly 4 for 4 cyl, and 5 for 5cyl.  Lots of other things would
need to be changed, but that is at least a start.
Bruce





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