The following was an unanswered post on the project Slack channel. Issue not decided, but leaning toward the header solution. 09/18/2021.
I am currently using KiCAD to build my interface board from my factory engine bay wiring harness to the Dropbear ECU. I have downloaded the board-mounted connector definition from componentsearchengine.com and placed it on my circuit board design. The Delphi connectors do not have a board footprint so I have used two generic 24-horizontal pin connectors. My OEM ECU has 52 pins, of which perhaps 25 tops will be used by the Speeduino. My engine originally used multiplexed fuel and wasted spark, but I have switched to a Hitachi R35 coil on plug setup and will be implementing sequential fuel and spark. These wires are coming to the ECU through two separate harnesses of six wires each. Should I add two additional 6-wire connectors to the interface board, or attach these 12 wires directly to the Dropbear side Delphi connectors? I am using low-impedance injectors and have built an external resister pack and I have not determined whether or not I need to add any relays. I presume if I must that they will be external to this board also. I am leaning in the direction of attaching these 12 wires to the interface board as it will provide a certain amount of strain-relief. Here is my design so far… Any suggestions to change or improve this approach is appreciated. Thank you. David