Spark Dwell Time?

[Blk02Ls1A4]

{B6001} Spark Dwell Time
"Dwell time is the amount of time (in ms) that the coils are charged before firing. If the dwell is set too low a weak spark can occur, if the dwell is too high there is a risk of overheating the coils."

Is the description that EFILive gives me, has anyone ever played with this table. I would think that increasing the dwell time would give a more powerful spark, for better efficiency/power. I have the MSD coils on my car so I would think that they could handle a little more dwell time, maybe 1-2 ms.

What doesnt make sense to me is that the dewll time to produce 1.0 Volt at 800 Rpms is 28.9, while the dwell time to produce an 8.0 Volt spark at 800 Rpms is 8.9. So the table indicates that it takes less time to make a spark of greater voltage. Anyone have any ideas?

[dfe1]

I think you're looking at things sideways. The volt axis refers to battery voltage. The lower the battery voltage, the longer the dwell time required to generate a spark of adequate intensity to reward you with the melodious sounds of internal combustion. I've played with the table a bit, but you'll probably need a dyno test to determine the performance difference. Not much "seat-of-the-pants" so far. The danger in extending dwell time too far is overheated coils, but I haven't pushed the envelope very far-- yet.

[01blkss]

f is 9...

Ok anyways i am just bringing this back to life cause it is the only thread that i got when i searched spark dwell time and would like to hear other opinions on it.

Thanks
Louie

[dfe1]

f is 9...

Ok anyways i am just bringing this back to life cause it is the only thread that i got when i searched spark dwell time and would like to hear other opinions on it.

Thanks
Louie

Actually, F is 15. If that doesn't make sense, you don't speak hexadecimal.

[01blkss]

ohh...lol

Yeah i as just using that as a way to get this back to the top...

But now i got you...i took a couple of EE classes.

[dfe1]

ohh...lol

Yeah i as just using that as a way to get this back to the top...

But now i got you...i took a couple of EE classes.

Then how about 7+1=10?

[ringram]

Only in base 8

[dfe1]

Only in base 8

Commonly known as octal. But the larger question is, does anyone have any information relative to altering spark dwell. Here we have 01blkss worried to death that his dwell times are too short and nobody is helping to ease his worries. This shouldn't be taken lightly becuse short dwell fear syndrome (SDFS) can have serious consequences.

I've experimented a bit with it, but I haven't seen much of a performance difference. Measurable gains may require extreme increases in dwell time or may not show anything unless spark energy is marginal. How about someone with easy dyno access doing a back-to-back test?

[white2001s10]

The factory ignition is already so good that without the presence of misfires I doubt any difference could be measured.
One would have to have very good test equipment and edge the tune to the point of lean misfires throughout a measureable RPM range. Then any improvement in ignition would be very measurable.
I've done this type of testing before, but unfortunately I do not have a test mule available at the moment. If something comes up in the future I'll definately keep this test in mind.
I would also like to know the answer beyond speculations on the web.

[techlink]

Coil saturation is not engine speed dependent it is dependent on inductive reactance. Once the coils magnetic strength reaches maximum flux density continuing to allow current to flow in the circuit only serves to generate series circuit heating. When you observe as many amperage traces that I have you quickly realize that heat reduces coil performance by increasing resistance and diminishing coil output proportion.
I should upload several screen shots of the flux density and amperage traces so that you can see that the values in these tables are very accurate to the data that I have gathered since 1986 introduction of GM Type 1 DIS. I would consider making changes to these tables only if the coil has been changed in capacity. Furthermore, as engine speed increases the time between the firing events gets closer in time. This poses the question in a single coil system... how far can you increase dwell before it has no time to collapse. A multiple coil system less dependent on rpm charge and collapse time periods.

Just my thoughts...