GenBoard/Manual/InputTriggerTypes [basic trigger requirements]

Hardware - analog side




Missing tooth






Simple coil type or N+1









Minimum number of trigger events - coil type trigger

The minimum number of required trigger events is equal to the number of ignition output events. This is called a "coil-type" (or even-type) trigger. For this setup, generally there is an ignition event (spark) for every primary_trigger events.

That means that it is not possible to fire

Using ignition with a coil-type trigger requires a distributor, or camsync: GenBoard/Manual/InputTriggerCamSync

Camsync (if conditions are met) allows any type of ignition, wasted spark or fully sequential ignition (eg. COP). Camsync actually allows the special case of not to fire for each primary_trigger events (skip them in sequence as defined by h[2] array), but there are limitations:

Multitooth - missing tooth setup

Missing-tooth crankwheel (60-2, 36-1, 24-1, 12-1 or other) is the most common (and very powerful) setup used on today's engines.

Missing-tooth trigger allows wasted-spark setup even without cam-sync. Wasted-spark is also called "direct ignition system"; "Direct", as it is without distributor. It is preferred to distributor setup:

Again, fully sequential ignition requires cam-sync. The benefits of fully sequential ignition are so small (only about 10% of the energy is wasted for the wasted-spark setup, but wasted spark transformers are usually stronger) that most people don't require the extra complexity.

There is an IGN_DUALOUT feature (requires firmware rebuild with IGN_DUALOUT in my_make) to allow Fully sequential ignition (eg. COP) without camsync, for some extra sparkplug wear ( MembersPage/DaveBrul has been using it for ages). This means there is a coil for each cylinder, that gets fired once per crank rotation (vs cam rotation). This is generally not recommended unless there is a good reason for it (eg. 5cyl engine with 60-2 crankwheel that by nature cannot use traditional wasted-spark). IGN_DUALOUT and 8 cyl will not work with either 60-2 or 36-1 (24-1 recommended) crankwheel (while 8cyl will work happily with either 60-2 or 36-1 in wasted spark output configuration).

the N in N-M must be a multiple of the ignition-output count

ignition-output count = cyl_count/2 for wasted spark, cyl_count otherwise.

Practically this means that 5 cyl and 36-1 will not work. 60-2 works basically with anything (60 is a multiple of 2,3,4,5,6,10,12, 8/2).