What is an appropriate dwell time for these coils?

[feelingsupersonic]

LS coils seem to have the best documentation for MSnS installs but I wanted to confirm with those who know are more experienced. They are from an LS series engine, but are not the traditional LSx coils that seem to make their way into distributorless conversions. They have the same wiring/pin assignment as LS1 coils.

Background: 1983 Porsche 944 2.5, Microsquirt V3 running latest MSExtra. I've had the following coils installed for the last few months and have put a few thousand miles on them, firing in wasted spark:



They are GM part # 12558693, and I can't seem to find objective information about these particular coils. Some people are saying 3.8 ms at most, and some say 6.1 ms (as per the MS sequencer coils page, that we all have been to a million times).

They are from a 2000 Suburban, junkyard special. I believe it was a 6.0 model.

So basically, I'm unsure if I'm running the right dwell time. They run great at 5 ms but at 3.8 ms, I swear the car feels like it lost 10 hp. Is it normal for a lower dwell time (but still reasonable) to impact performance that much? I'm running a 0.045" plug gap. The stock plug gap for this engine (dizzy setup) was 0.028-0.032" which I ran for a while. They are resistive plugs. The stock spec for the Suburban is 0.050" so I figured I would try what I have now.

Spark looks great, the coils are healthy. Any advice?

[feelingsupersonic]

Forgot to add.. do I need to do any physical altercation to the MicroSquirt itself? I remember reading on here that there's a physical jumper or switch you would flip on the older MicroSquirts to change the output from direct drive to logic level (with the default being direct drive). Since these are LS coils they are logic level. Besides the settings in TunerStudio, is that switch/jumper there on V3 Microsquirts? It hasn't been opened... I bought it new from DiyAutoTune in June 2015. It runs smooth and never misses, but should I bark up that tree?

[dontz125]

The uS V3 has no heavy drivers, and is logic-only.

[elutionsdesign]

Are they getting real hot? Excessive dwell means excessive charging which translates into excessive heat and early coil failure. If they seem fine (hot from engine bay heat but not unduly hot) then I'd be inclined not to worry.

[feelingsupersonic]

Thanks for the replies gentlemen. They seem to be fine at 5ms nominal dwell, and it starts fine at 5ms cranking dwell.

I'm going to close the gap a little, I think 0.038 is more appropriate after doing some research on Chevy forums.