News: Putting FUN and FRIENDLINESS, FIRST into owning and learning about AMC small bodied cars, primarily Eagles, Spirits and Concords as well as vehicles built in AMC's Mexican subsidiary, VAM.

The AMC Eaglepedia can now be accessed using the buttons found below  This is a comprehensive ever growing archive of information, tips, diagrams, manuals, etc. for the AMC Eagle and other small bodied AMC cars. 

Also a button is now available for our Face Book Group page.


Welcome to the AMC Eagles Nest.  A new site under "old" management -- so welcome to your new home for everything related to AMC Eagles, Spirits and Concords along with opportunities to interact with other AMC'ers.  This site will soon be evolving to look different than it has and we will be incorporating new features we hope you will find useful, entertaining and expand your AMC horizons.

You can now promote your topics at your favorite social media site by clicking on the appropriate icon (top upper right of the page) while viewing the topic you wish to promote.


  • May 23, 2022, 05:02:26 AM

Login with username, password and session length

Author Topic: GM 4-pin HEI Ignition Module vs newer higher current 7-pin???  (Read 936 times)

0 Members and 1 Guest are viewing this topic.

Offline Canoe

  • Eagle Sundaancer
  • ******
  • Posts: 1149
  • Thumbs Up 54
    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]
« Last Edit: July 05, 2020, 02:54:15 PM by Canoe »

Offline Canoe

  • Eagle Sundaancer
  • ******
  • Posts: 1149
  • Thumbs Up 54
Re: GM 4-pin HEI Ignition Module vs newer higher current 7-pin???
« Reply #1 on: July 05, 2020, 08:47:44 AM »
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.
« Last Edit: July 05, 2020, 02:53:48 PM by Canoe »

 

SMF spam blocked by CleanTalk