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...:)

[joecar]

I'd like to see the traces you speak of, please... :)

[techlink]

I will have to see if I can either upload them here or just put them on my web site.

I'll do that this weekend...

I'll post several of the GM Ignition patterns and traces for comparison and analysis.

regards
techlink

[joecar]

If you need images hosted, try http://imageshack.us/

[techlink]

Here is a sample of the Coil saturation patterns I spoke of... This is a tutorial I put together to demonstrate the reason there is dwell correction and why it should not be changed.

Regards
Techlink

If you want it I'll email you the Flash file
This link does not work here.

http://forum.efilive.com/attachment.php?attachmentid=718&stc=1&d=1151318513
Coil Primary.png

[joecar]

Could try hosting at cardomain or photobucket.

[emarkay]

Interesting. What other areas of automotive expertise have you, Techlink?

[techlink]

I just love to play with vehicles and engine controls...
I write service manuals and technical documents for others and facillitate training classes and such... I still work on vehicles, testing and experimenting.
Emission controls and other technologies.

[redhardsupra]

heh, we got us a keeper:)
and hpt board is getting flooded with newbies asking questions about tuning their cavaliers and cobalts... HA!

[joecar]

Very instructive, do you have more...?

[joecar]

Question: with the low ohm spiral wound conductor spark plug wires, is there a way to pick up the induced current thru the wire since the spiral arrangement does a very good job of cancelling out the field outside of the spiral (...my inductive clamp can't pick up any signal, so my scopemeter can't trigger...)...?

Edit:... I can try to clamp the clamp around the coil HT terminal where the wire attaches.
Edit:... I can explain why spiral wound wires have virtually no mag. field lines outside the spiral (I should be able to...).

[techlink]

We have lots I don't think we will ever run out.

Right now we are writing a tuning manual that covers many of these areas in extreme detail.

Thats what we need to finish by august 30th

So right now we have permission to use HP tuner screen shots but that is only part of what I need to give it its own section ... I need to evaluate several tuning examples good and bad. From this we will enhance this product and the skill level of the tuning forum.

Regards Techlink:)

[techlink]

Measurement Description Coil Near Plug
Multi-Port Fuel Direct
Injection Injection—Gasoline
Energy (1000 V zener load) 90 mJ Peak secondary current 110 mA (1000 V zener load)
Spark duration 2.0 ms (1000 V zener load)
Secondary voltage 40* kV
Secondary load 30 pF
Primary resistance 0.43 ½
Primary charge time (14 V) 3.1 ms
Nominal primary current 12.5 A
Weight 370 g

To to prove the life expectency of the coil you would to a long term durability test. Where 1 life = 233 hours of testing using this method.

Notice that the maximum is 12.5 amps @ 14.0 Volts

and charge time is max @ 3.1 ms?

Regards Techlink

[hquick]

Really old thread....but not too many others on this subject.
In my never ending quest to understand my Burb better....I've been looking through my tune and comparing to other 'similar' tunes.
As I've swapped from a 98 PCM to the 0411 99+ LS1 pcm...there are some differences...mainly alot more/different parameters.
One really BIG difference is the B6001 table.
I'm getting 'pinging' at low rpm, high-'ish' load so I'm looking 'everywhere' for the issue/cause.
Can someone explain to me why there is such a big difference in the B6001 tables between the L31 and LS1?

[dfe1]

Really old thread....but not too many others on this subject.
Can someone explain to me why there is such a big difference in the B6001 tables between the L31 and LS1?
See if this makes sense-- an L31 has one coil, an LS1 has 8 coils and time is of the essence.

[hquick]

Thanks...but I'm NOT Batman and you're NOT the Riddler.:laugh:
Just stirring mate.

Actually I was curious because there are some things which didn't seem to 'fit' after the 98-99+ PCM swap.
Is that first line so much higher because that's during cranking?
I guess I'm just clutching at straws....

[dfe1]

You had me scared for a minute-- I thought you were going to say you wished I was Robin. If you look at the graphs, the values are closer at lower than at higher rpm. I think it all has to do with time available. If you run the numbers, you barely have enough time to charge a coil when you're trying to fire 8 cylinders at 6000 rpm. With 8 coils, you have all the time in the world to fully saturate a coil before you fire it. Keep in mind that with a point-triggered system, dwell time is limited by the mechanical limitations of opening and closing a set of points every 45 degrees of distributor rotation.

[hquick]

Thankfully I have no idea what you look like..so I can't picture you in yellow tights. :shock: :laugh:

Thanks for the explanation

[SSpdDmon]

Thankfully I have no idea what you look like..so I can't picture you in yellow tights. :shock: :laugh:

http://www.motownmuscle.com/forums/images/smilies/theyareontome.gif

[dfe1]

Thankfully I have no idea what you look like..so I can't picture you in yellow tights. :shock: :laugh:

Thanks for the explanation

Now I'm really scared. The fact that you're even thinking about picturing me in yellow tights...

[joecar]

roflmao... :rotflmao: ...I really don't know what to say... but this is funny... :Nothing_funny_to_ad

[hquick]

Yep! But just a little bit scary. :eek: :mrgreen:

[dfe1]

A LITTLE scary??-- maybe for you, but look at it from my perspective. Here I am trying to help with a technical question and I wind up as an imaginary internet forum pin-up in yellow tights. And NO, you may not have an autographed photo.