MicroSquirt.com read only forum (Jan.15,2018)

When using a GM 8-pin, external coil distributor what should the "Maximum Spark Duration (ms)" setting be set to in the "Ignition Settings" drop-down box?
I have it set at 2 right now.

Also, in the "Dwell Settings", I have the Max Dwell Duration set to 2.5 as I remember reading that this is the standard rate for the GM external coils as opposed to the "in-cap" coils which are normally set to 3.5

Is all of this okay?
Thanx,
Bud
MS-II/ V2.2 /MT2-25

Bud,

Yes, those are okay. Maximun spark duration is the amount of time MS-II tries to wait after a spark before starting to charge the coil again.

MS-II tries to fit the dwell time + max. spark duration into the time between sparks. If it can fit them, then the full dwell time is used. If the time is too short (because the rpm is high) to fit both the dwell and the max.spark duration, than both are shortened proportionally.

If the charging starts too early, no energy is put into the coil, it simply dissapears into the ionized current at the plug. So you want the max spark duration to reflect the actual spark duration, not shorter.

If the max spark dration is too long, however, then the actual dwell value gets shortened at a lower rpm, limiting the spark energy at higher rpms.

A value of 2.0 for max spark duration is typical, but you can try as low as 1.5 if you have high rpm misses.

And yes, for the external HEI coil, use about 2.5 (or a bit higher if you have misfires), for the in-cap coil use 3.5 (or a bit higher).

Lance.

Thanx Lance