Accel enrichment

[Ludis Langens]

Bruce Plecan <nacelp at bright.net> wrote:
> Well while your all at this maybe some one could explain the GM
> strategy (at least with the 747 ecm), why they have the IAC jump
> open, and then slowly close back down again, when making large
> or small throttle opening changes.  Would "seem" a-- b---------s,
> since it would reguire more acceleration enrichment to cover this
> addition "hole".

I checked some listings.  Two different ECM's (one PFI, one TBI) both
kick the IAC open (a specific number of counts) when the throttle is
closed faster than a threshhold.  The IAC is then allowed to close
slowly.  A likely purpose for this IAC kick is to "catch" the engine as
it slows to idle RPM.  I don't know what the '747 does because it's code
is significantly different.

And oh, yes, there is extra acceleration enrichment when the IAC is
being kicked open.

               unsigned long BinToBCD(unsigned long i) {unsigned long t;
Ludis Langens     return i ? (t = BinToBCD(i >> 1), (t << 1) + (i & 1) + 
ludis at cruzers.com            (t + 858993459 >> 2 & 572662306) * 3) : 0;}