730 Spark Advance

[rrauscher at nni.com]

On the gmecm web site, under the '747, there is a write-up
on how the spark works. It is similar to how it is done
on the '730. Covers inital, bias's, and the math.

I think that the way Gm implemented hiway spark was to
pass emissions testing. I've just added what worked to
the main spark table, and let it at that.

BobR.

>I'm doing some last minute tuning on the spark tables, and need to get a
>few things straight.   Base cal is AUJP.
>
>1.  The actual measured timing at the crank is the amount in the table (32

>degrees for example), subtracted from the inital advance (6 degrees in
>AUJP).   Measured at the crank, this would be 26 degrees?    This is what
>the scan tool reports as spark advance. 
>
>2. Is the value for max advance at $026 is the max advance the ECM will
>allow to be delivered, or the max value allowed in the table?  Given that
>$026 is 39 degrees, the max advance possible measured at the crank would be

>39 + 6 = 45 degrees?      If this is correct, a value of 42 degrees in the

>table would result in 38 degrees crank advance, right?
>
>3.  What are average highway cruise SA numbers?  I realize this varies
>greatly, but what's a ballpark?  Stock AUJP table looks to only put in
>about 31 deg. at highway cruise, less than I'd expect.
>
>4.  Is there a good reason to use "Hiway SA mode" instead of just directly

>tweaking the spark table?   
>
>-> Bob Valentine
>-> bob at tecmark.com
>
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