dwell time and spark duration

[firefoxx04]

Ive been doing alot of looking on various sites and it seems like no one really knows what max spark duration really is and how it effects the driveability of their cars.

my msd coil is supposed to have between 2.5 and 3ms of dwell. i have a v6 engine with a single coil so i set the dwell at 2.9ms (and assumed that was fine, even at 6500rpms)

but what about max spark duration? its at .6ms. Im fighting a sputtering (not violent) issue at 2500-3000rpms that happens to only be there at light load. I wont go into detail on the other things im doing to try and fix it but i want to be sure all my settings are correct so i can rule that out. dwell was at 2.7ms, i want to see if 2.9 helps. for all i know, spark is unrelated to my problem.

if it matter, msd blaster 3 coil with my MS2 running a sohc 6g72. single coil.

also, what is overdwell and underdwell? i remember reading they do nothing (still in development?)

thanks guys

another thing, dwell acceloration compensation. mine is at 1ms.

[myk777]

I think it's explained pretty well in the manual, see below

http://www.msextra.com/doc/ms2extra/MS2 ... tm#moreign

Mike

[firefoxx04]

so max spark duration is the time before the coil charges again after it fires?

so would it be how long the coil is firing for?

im thinking more max spark duration would mean for a better spark.

[bubba2533]

From my interpretation of the manual I think..

so max spark duration is the time before the coil charges again after it fires?

Yes.

so would it be how long the coil is firing for?

Umm, not sure. See my edit below.

Edit: Actually now that I think about it you may be right about the second point also. It may be just a delay which allows spark to occur, which i suppose can only happen if you do not immediately start charging the coil right after the field is allowed to collapse.

This will only really matter if you have an ignition setup which you will have limited time between spark events. This can be a combination of many things, such as high rev limit, large required dwell times, and low number of coils.

I would think that dwell and max spark duration should have nothing to do with your sputtering if you are running the recommended dwell. Especially if you are not having problems at higher than 3000 rpm.

[firefoxx04]

yeah i doubt it has anything to do with my sputtering. But if i can get the spark plugs to fire longer, that can only be better right? ill see what the other MS guys are running on this engine

to me it seems like if the coil isnt charging, it should be firing. why would it sit idle? i guess if it happened to find its self idling between two cyl (if that makes sense) but then again, it should be charging if its not firing (in my mind) but i guess that would need an actual map to tune the coil for certain RPM ranges so its always charging when it can and then firing when needed but i think im thinking WAY TO HARD about this

it pulls hard to redline so im sure my coil settings are fine, i just wanted to make sure i understood what they meant

[bubba2533]

yeah i doubt it has anything to do with my sputtering. But if i can get the spark plugs to fire longer, that can only be better right? ill see what the other MS guys are running on this engine

to me it seems like if the coil isn't charging, it should be firing. why would it sit idle? i guess if it happened to find its self idling between two cyl (if that makes sense) but then again, it should be charging if its not firing (in my mind) but i guess that would need an actual map to tune the coil for certain RPM ranges so its always charging when it can and then firing when needed but i think I'm thinking WAY TO HARD about this

it pulls hard to redline so I'm sure my coil settings are fine, i just wanted to make sure i understood what they meant

It sits idle because you don't need to charge it all the time. It's designed for the worst case (i.e. high rpm) so the time required to charge it is very short. And when you are at a lower rpm you have more time to charge it, but that doesn't mean it will give you a hotter or a longer spark.

Because it was designed to be fully charged in a short amount of time, you will only be wasting energy by charging it more then required. It will overheat the coil, and could even burn it up if you charge it too long.

Read that page that was linked to a few times. It's difficult to understand the first time, but it will give you a better understanding of whats going on.

[firefoxx04]

okaaay im starting to get it. thanks for the quick response guys