spark dwell...can somebody give heavy details

[S2H]

I would like to see a serious discussion about spark dwell...
what it can do if you increase or decrease it...
maybe how to properly increase or decrease it for more torque/horsepower
what negative effects it can have
maybe somebody explaining it in a very technical way??

can anybody on here do this??

[rays_vet]

A guy on ls1tuning.com named wait4me increased a guys torque by 8 or 10 simply by changing the dwell. I posted on that site as well asking what he did. he posted back values he changed but at that time I was using ls1edit
which does'nt have that feature. now using hptuner and hope to persue in that table as soon as I get the ve tables nailed down!!!!

[jimmyblue]

The energy stored in a coil's magnetic field
is proportional to the current. But people who
work with magnetics, like power supply dudes,
seem to prefer to talk about volt-seconds.
Volts, here, is your IGN voltage and seconds
is your dwell time. The longer you light up the
coil the more energy is stored, later to be
dumped as cylinder spark. Hotter spark.

Now, there are some limits to this. Every core
type coil (other than air) has an enhanced
magnetic storage from that core's little mini-
magnet "domains". The solenoid field's effect
of re-orienting these temporarily is work, that
can be taken back out with low loss, all much
greater than the effect of pushing field through
air. But when all of the domains have been
torqued straight, so to speak, there's no more
work left to do and nothing much (except the
plain field increase) to oppose current increase.
The coil is said to "saturate", any more work
you put in, you don't get back, and the current
goes through the roof. "Ouchie", says Mr. Coil
Driver.

In a cyclic system you need to divide your time
between charging and discharging the coil. Too
much dwell at high RPM might well be impossible,
or would mean you'd be cutting into the prior
spark event's discharge tail. I don't know if an
excessive commanded dwell will be ignored, or
clipped, or possibly cause an inappropriate early
coil driver turnon.

So anyway there are limits to the maximum dwell,
both practical time-slice ones and damage- and
inefficiency-related ones. Below that point, though,
more dwell = hotter spark and that's generally a
minor bonus to burn quality, an earlier- and better-
established flame kernel.

[Chris@HPTuners]

according to my sources, 6-8 ms is the max you sould take it otherwise coil lifetime degrades dramatically.

[S2H]

so which part is it that I would play with???
base dwell vs rpm ign??
base dwell modifier vs ign V vs ect??
or something else??

and does anybody have some values for a 2000 LS1 engine that worked and would be a good safe squeeze of a few more ponies..even though it might only be 3 or 4 HP

[rays_vet]

A guy on ls1tuning.com named wait4me increased a guys torque by 8 or 10 simply by changing the dwell. I posted on that site as well asking what he did. he posted back values he changed but at that time I was using ls1edit
which does'nt have that feature. now using hptuner and hope to persue in that table as soon as I get the ve tables nailed down!!!!

If you go to that site he left some data on dwell. A search with torque in the topic in the advance section should get you close.

[S2H]

If you go to that site he left some data on dwell. A search with torque in the topic in the advance section should get you close.

I cant seem to get to that site....
it keeps telling me that it doesnt exist?????

can anybody else get there????
I have tried from 4 different computers...each at a different location and IP...I cant get anything to come up...
though I do a whois.sc search and I get it.....?????

[MNR-0]

I think you're chasing the wind here. Even on a mildly modded LS1 spark dwell won't amount to anything significant, not even a few ponies. Thats for supercars and very high RPM engines where burn rate becomes a big factor. On our stockers, spinning to 6500RPM, you won't see any noticable gains - if any.

Running the plugs hotter is not a wise move IMO.

[Chris@HPTuners]

also useful on FI cars, where denser mixtures play a part.

[02sierraz71]

how about on NA engines you would think better spark more complete combustion less chance of detonation

[Chris@HPTuners]

how about on NA engines you would think better spark more complete combustion less chance of detonation

Never done the test myself. No doubt there is a point where you are just burning out your coils for no good reason.

GM probably set the dwell for a lifetime of troublefree coil operation, i dunno what their definition of lifetime is. But i am told anything over 6-8 ms reduces it to months, not years.

[02sierraz71]

Never done the test myself. No doubt there is a point where you are just burning out your coils for no good reason.

GM probably set the dwell for a lifetime of troublefree coil operation, i dunno what their definition of lifetime is. But i am told anything over 6-8 ms reduces it to months, not years.

thanks for the reply chris, I raised the base table so my max would be 7.28 it does seem to help I can run more timing easily with less kr.

One more question what are the guidlines that the max and min tables go by Id rather not just set them to 1 as they have to have a purpose. I logged ignition voltage and it varied only from 13.4 to 13.6 idle to wot
the base table covers a huge range of voltages no of them I ever see.

[Chris@HPTuners]

the max and min tables limit far the base dwell can be modified. I believe in all stock cals they are set to the maximum of 1.3 and min of 0.9.

In most cals the dwell time is modified slightly by battery voltage and coolant temp.

[02sierraz71]

the max and min tables limit far the base dwell can be modified. I believe in all stock cals they are set to the maximum of 1.3 and min of 0.9.

In most cals the dwell time is modified slightly by battery voltage and coolant temp.

When are the max or min modifying tables used are they always used or is it just under certain conditions

[Chris@HPTuners]

always.

[EC_Tune]

Different coils have different lifespans but from what I understand 6 msec continuous will give you 200K miles. 9 msec will give you less than 30k miles on brand new coils. I always limit it to ~5.5 - 6.2 msec with a slight boost at high MAP.

EC

[MeentSS02]

What do stock-ish tunes command for dwell?

[MeentSS02]

Oh well...changed it, so we'll see how long my coils last

[Screamn03]

Oh well...changed it, so we'll see how long my coils last

Do you notice anything different with the way it runs?

[MeentSS02]

Throttle response seems to be a bit better, and WOT seems to be a bit nicer, but no numbers to back it up. I didn't change the values much...I took them from 4.0-ish to 5.5-ish milliseconds (never going higher than 5.8 ms).