GM 4-pin HEI Ignition Module vs newer higher current 7-pin???

[Canoe]

I've been seeing posts around the internet about using GM's 7-pin IG modules instead of the usual GM 4-pin HEI modules, but details aren't given (that I've found).
Now I've found a resource on the modules that provides info that seems to back this up.

http://gpzweb.s3-website-us-east-1.amazonaws.com/Ignition/HeiModules/HeiModules.html
http://gpzweb.s3-website-us-east-1.amazonaws.com/Ignition/HeiModules/Hei7pinDR124moduleNotes.txt

It appears that we could use the more modern higher current 7-pin module in place of the 4-pin module by:

• +: Positive power ~12 VDC
• C: Coil; connects to negative terminal of coil (module uses low-side current sensing to limit current when necessary)
• P: Positive of distributor pickup
• N: Negative of distributor pickup
• E: not connected / not used
• R: not connected / not used
• B: not connected: module uses the pickup inputs to drive the module's Dwell circuit, hence the coil
• ground the module through the hole

And we might be able to use the B/Bypass tab to control between running in the mode above (Bypass) or in Run mode to use the MCU to control the timing & dwell. Using the MCU would allow it to control for Ping from the knock-sensor. This is speculation on how it might work:

• +: Positive power ~12 VDC
• C: Coil; connects to negative terminal of coil
• P: Positive of distributor pickup
• N: Negative of distributor pickup
• E: ECM input returned from ECM, drives coil using ECM timing & dwell. Return from Eagle MCU may be compatible to control timing & dwell???
• R: Reference signal: DC generated from distributor pickup to ECM. May be accepted by Eagle MCU in place of the distributor pickup signal???
• B: Bypass:
  • 0/not connected: Bypass ignores any E signal and uses the pickup to drive the module's Dwell circuit, hence the coil
  • +5 VDC voltage (higher?): module uses the E signal to drive the coil
• ground the module through the hole

NOTE: if I understand corectly, you have to turn off and restart to change Bypass modes. Which seems odd, as Bypass is also referred to as Start mode. I suspect the module wouldn't get confused and would be happy to start in Start mode and then switch to Run mode when the B tab changed.

Too bad we don't have a map of when the Eagle MCU changes timing/dwell. Or is dwell controled in the stock IGM?[/list]

[Canoe]

I suspect the module wouldn't get confused and would be happy to start in Start mode and then switch to Run mode when the B tab changed.

Found out that is exactly how it works in normal operation, 0 VDC provided to the module Bypass tab by the ECM when starting, and 5 VDC provided by the ECM once started and in Run mode.

And the 7-pin has been used to replace the 4-pin using

It appears that we could use the more modern higher current 7-pin module in place of the 4-pin module by:

• +: Positive power ~12 VDC
• C: Coil; connects to negative terminal of coil (module uses low-side current sensing to limit current when necessary)
• P: Positive of distributor pickup
• N: Negative of distributor pickup
• E: not connected / not used
• R: not connected / not used
• B: not connected: module uses the pickup inputs to drive the module's Dwell circuit, hence the coil
• ground the module through the hole

Unclear is compatibility with our distributor pickup output.