747 Timing Calc

[rr]

The ALDL spark gets added when the ECM is in ALDL mode.
I believe this is the 10k resistor across the diag
terminals. Scan tool can also be used to do this.

As for the 13deg, hard to say. I haven't tuned many lo-po
motors. Gm needs to take into account emissions, cat-con
survival and warranty claims. Hopefully someone with more
experience in this area can add.

C2500, a heavy truck maybe? Low timing to keep ping at
bay while towing and engine is hot (220f).

BobR.

On Wed, 20 Jun 2001 17:46:02 -0400
 "Brent" <wildkat at paonline.com> wrote:
> I assume that I did the calculation correctly.  I really
> wasn't sure whether
> to include the "ALDL/CL adv " or not.
> 
> Amazing yes and confusing.  I don't understand why it
> only needs 13d @
> 3200rpm WOT.   I thought the older iron heads had a slow
> burn rate as
> compared to newer alum heads and required more WOT
> timing...
> 
> Seems to indicate the mixture is burning very rapidly or
> end combustion is
> taking place in the exh manifolds.    Thoughts?
> 
> Regards,
> Brent
> ---- Original Message -----
> >
> > Amazing isn't it?
> >
> > BobR.
> >
> > Brent wrote:
> >
> > > I'm having trouble figuring out how the 7747
> calculates timing.  This
> stock
> > > bin is for a '91 Chevy C2500, 350, auto, 3.73.
> > > http://www.paonline.com/WildKat/arjt000.bin
> > >
> > > Lets run the engine at 3200RPM, PE mode, 100KPA, 75d
> C coolant temp.
> I'll
> > > assume there is no knock retard.  I used WinBin to
> find the values.
> 
> 
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