Add in ignition systems as a feature in the engine builder.
to keep this simple ill just name a few ideas
* on earlier distributor engine eg early nissan pintara 2.4l they ran 8 plugs on te I4 which was to help combustion power/emission wise
* coil per cylinder options
* the use of wasted spark ( throws a spark on exhaust stroke to burn any unburnt fuel therefore reducing emissions )
* high energy coils
just a few thoughts