Ignition output configuration can be one of the most difficult areas of ECU wiring and one that often causes the most confusion. A large part of this complexity comes from the huge number of different ignition types that are available, with there being significant changes in the hardware used in the late 80s and throughout the 90s compared to newer designs.
Whilst this guide does not cover all ignition styles and hardware, it does cover the most common scenarios. Generally, it is recommended (Where possible) to use newer styles of ignition hardware (Typically 'smart' Coil-on-Plug or Coil-Near-Plug) rather than utilising separate igntion modules.
Wasted spark is a common means of controlling spark that requires only half the number of ignition outputs as there are cylinders, with 2 cylinder being attached to each output. EG:
Wasted Spark has the advantage of not requiring any cam signal or input as it does not need to know the engine phase. This is possible by firing the ignition outputs once per revolution and pairing that output to 2 cylinders that are both at TDC (With one cylinder on compression stroke and the other on exhaust)
There are many dual pole, wasted spark coil packs available both with and without built in igniters. Either are suitable for use with Speeduino, but use of coils with built-in igniters is recommended
Sequential ignition control using Coil-on=Plugs coils dramtically simplifies the ignition wiring. With this configuration, each coil (and subsequently each cylinder) connects to a single ignition outpt, wired in the firing order.
If a distributor remains in use, only a single output is required from the ECU. This should be fed into a single channel ignition module (Such as the common Bosch 124) which can then drive the coil.