[Gmecm] IAC / AIS Setup - $8D/7730

[Jay Vessels]

Hi there!

I just posted something about this, but basically GM's method gets you 
to about 30 IAC counts, or about 10-12% of it's full range, at hot idle. 
  On TBI systems, many want as much air going through the TBI as 
possible to get better atomization, and adjust minimum air to get to 
about 2-3 counts (about 1% of full range).  You want some headroom so 
the IAC can adjust the idle speed down in case the engine wants to idle 
up for some reason.  If you don't have enough headroom the IAC can't 
compensate for a too-high idle.

Jay Vessels
1982 Chevrolet S-10 Sport, 2.8V6 TBI
1984 Chevrolet S-10 Blazer Sport, 2.8V6 (TBI pending)

Clair Davis wrote:
> I'm still sorting out the tuning of my slightly-hotter cam that I described
> previously in the "Adjusting 7730/$8D for larger cam" thread, and I came
> across an issue setting up the IAC / AIS motor that I thought I'd ask about.
> This is from the user manual for an Accel DFI system, but it applies here, I
> think.  They basically suggest setting up the IAC so that it contributes
> very little, if anything, to the base idle speed.   Say you want a 750-rpm
> idle, set the throttle plate opening to achieve 700-rpm or so at operating
> temp, and let the IAC give you the last 50.  That's not how I remember the
> GM procedure, which (as I recall) is to disable the IAC and shoot for the
> lowest idle figure that can be sustained - maybe even 4-500 rpm.  That's
> essentially how I have mine set up now, but it seems to make sense to set
> the idle higher if possible and just let the IAC do the fine tuning.
> 
> Is one method preferable over the other?  I guess as long as the idle speed
> is specified in the code, it doesn't really matter, except from the range of
> motion the IAC sees.  Comments?
> 
> Thanks in advance,
> 
> Clair
> 69 Valiant '730
> FTWTX