[Gmecm] Piggyback ignition modules

[Andrew Gibson]

Zaphoid, I like your thinking with using the 7 pin module to drive the second module. I have been worried about the stalling concern, not because of actually stalling the truck, but the initial starting problem. Why put efi on if it's a hassle to start? Once running the truck runs great though.
   
  As for the tunercat's timing tables, they have a maximun spark relative to reference value and spark reference angle. No minimum. They list the max as a 8 bit value of 00. With the value they claim is right (all the 7748 bins have it at 00 there) the math that Shannen gave us earlier doesn't work. Nor can it work with any of the other timing tables in the bin. I have found 3 places that are FF83, FF8E, and FF6C that are more likely right. Since TC didn't list what those addresses referenced to, I want to play a little and see if I can figure it out.
   
  The 7748 is a bare bones P4 ecm with cruise. Unfortunately the dissasemblies are different. The table locations are in different places and different sizes. Tearing into the rom info is a little scary at this point as I havn't researched it yet and previous attempts on this ecm yielded nothing. It just hasn't been done. At this point I would like est function, but if I can't get it I will live. I would also like to see if I can make the 7748 switch from a 4 cyl id to a 6cyl so I can get a full rpm range and not have to add 50% to everything that is related to rpm. Fuel, piece of cake, just add according to the displacement change per cyl. For me it was 10.5%
   
  Like I said, It runs good. (And I've only burned 2 proms!) It's just a pain in the neck to start.

		
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