spark ignition dwell time

[neo240sx]

here is the setup im using. http://forums.nicoclub.com/post3419200.html?hilit=coil#p3419200

I have a 10 gauge wire suppling the power directly from the battery via a relay.
I'm not really sure about the dwell time because I dont really know how to test it. But as far as I know its working. I guess theres not ignition module to limit the coils from overdwelling I've just been using the stock J30 igniter to run it.

 

[neo240sx]

Its odd because off boost I can rev clear to 7k with no problems on boost it breaks up at around 4800

 

[turbobuick]

Its odd because off boost I can rev clear to 7k with no problems on boost it breaks up at around 4800

Increased cyl pressure will need increased spark energy to jump the gap.

You will likely need a CDI box like Todd and I have referred to previously.

I would Google inductive vs capacitive disharge ignition and do little reading. There is some good stuff out there that will help understand your issues and help you make an educated decision on how to fix it.

Going to LS based coils may work if you run 6 individual coils that will fire only once every 720*. This way you will have plenty of time to increase dwell to saturate the coil. I do know not all LS based coils work the same and some start to clip coil output at 6ms in order to prevent overheating. You will have some trial and error with going to that setup PLUS you will need an aftermarket system that'll run it. They are not meant to work with an ignition module or ignitor. Cal hartline has a system like this running on a buick making decent power using a FAST XFI and XIM box that seems promising.

FYI I did run a 100% bone stock Buick DIS ignition system to 8.70's at 159mph+ making roughly 1200hp. My engine RPM was 6800 or less though. I dont think I would've been able to continue running it at the levels we ended up reaching due to the RPM needed to run faster. Another interesting point is coil packs didnt seem to last very long. I was eating them up pretty quickly at that level and it was the primary reason I switched to a distributor and CDI ignition. Might want to look at the Accel ICM box. Pretty trick and will run pretty much any ignition strategy you can think of.

 

[turbobuick]

Does the Nissan ignitor run 6 individual coils? If so why switch to a system that fires the coil once every 720* to one that fires every 360*??? Seems to me a step backward?

 

[neo240sx]

Does the Nissan ignitor run 6 individual coils? If so why switch to a system that fires the coil once every 720* to one that fires every 360*??? Seems to me a step backward?

Well my original system was coil on plug with no ignitor (it is in the coils). The coils where failing because of age and new ones are $500+ shipping so I wanted to try something else. I guess it would be easier to just go back to a coil that just fires once with plenty of time for saturation. I cant run a distributor so that leaves me not able to use most of the msd stuff.
I guess I just have to go back to an ignitorless coil on plug setup.

I dont see how you were able to run this setup to 1200 hp and I cant get 300 out of it. I usually shift at 6800 as well due to crappy cams. Maybe I just got a bad box. What type of plug and wires were you running? would that even make much of a difference?

 

[TurboTR]

Thanks Chris. My guess is, the coil packs tend to go south faster when they are made to misfire more and/or deliver max secondary voltage. The plug gap gets harder to jump with increasing load, which drives the secondary inductive voltage higher before the arc over starts across the gap. In your case the arc was likely pretty hard to start at wot relatively, so it would always be running the coil secondary at max voltage, which would tend to find and exploit the weak spots in the secondary insulation faster among other things.

And if the plug gap does not fire, well that max secondary voltage then found the next weakest link, and went somewhere that it was not supposed to.

I think that a blown spot in secondary insulation is probably what makes a coil pack start "popping" at wot then and be discarded.

Hope that makes some sense at least.

TurboTR

Increased cyl pressure will need increased spark energy to jump the gap.

You will likely need a CDI box like Todd and I have referred to previously.

I would Google inductive vs capacitive disharge ignition and do little reading. There is some good stuff out there that will help understand your issues and help you make an educated decision on how to fix it.

Going to LS based coils may work if you run 6 individual coils that will fire only once every 720*. This way you will have plenty of time to increase dwell to saturate the coil. I do know not all LS based coils work the same and some start to clip coil output at 6ms in order to prevent overheating. You will have some trial and error with going to that setup PLUS you will need an aftermarket system that'll run it. They are not meant to work with an ignition module or ignitor. Cal hartline has a system like this running on a buick making decent power using a FAST XFI and XIM box that seems promising.

FYI I did run a 100% bone stock Buick DIS ignition system to 8.70's at 159mph+ making roughly 1200hp. My engine RPM was 6800 or less though. I dont think I would've been able to continue running it at the levels we ended up reaching due to the RPM needed to run faster. Another interesting point is coil packs didnt seem to last very long. I was eating them up pretty quickly at that level and it was the primary reason I switched to a distributor and CDI ignition. Might want to look at the Accel ICM box. Pretty trick and will run pretty much any ignition strategy you can think of.

 

[turbobuick]

Well my original system was coil on plug with no ignitor (it is in the coils). The coils where failing because of age and new ones are $500+ shipping so I wanted to try something else. I guess it would be easier to just go back to a coil that just fires once with plenty of time for saturation. I cant run a distributor so that leaves me not able to use most of the msd stuff.
I guess I just have to go back to an ignitorless coil on plug setup.

I dont see how you were able to run this setup to 1200 hp and I cant get 300 out of it. I usually shift at 6800 as well due to crappy cams. Maybe I just got a bad box. What type of plug and wires were you running? would that even make much of a difference?

You could run a distributor if you wanted but it would take a lot of fab and in the end might not be as good as the COP setup.

I would use a NGK plug or Autolite racing. Stay away from irridium and platinum plugs. Use good plug wires like Moroso or MSD. Tighten the gaps to 23-25 thou. All of this can make a HUGH difference.

MSD does make CDI boxes for the DIS system but they are crap IMO. Not a big fan of MSD.

 

[S2V6RACER]

6 ms is plenty if I remember correctly.


But.

at 5000 RPM you have 12ms to fire the coil 3 times. which gives you a max of 4ms, if you had no "off time".

I would think that the BS3 will handle this for you, and force your dwell to shorten as you climb in RPM, perhaps you can see it on a datalog.

what is your dwell set to at the moment? if you hold the boost down, does the breakup happen at a higher RPM?

Bob

Bob, the DIS BS3 system (PTE Buick box) does not have user adjust-ability for dwell time. I would recommend a stand alone COP setup from BS3 with the external 24x wheel and use the GM coils. This system has been proven reliable to 13,500 RPM. As far as fabrication work, you will need to deal with a 1/2" thick wheel and a way to hold a 3/4-16 pickup like a MSD external crank trigger. No biggie.

 

[fog]

The Buick coil pack ignition has internal current limiting. Increasing the dwell beyond a certain point only heats the ignition transistors and the coils.

Duttweiler gave me one to play with several years ago, to see if I could soup it up. I was able to unpot it and reverse engineer it.

I added the wires so I could test it without the Weatherpack connector.

Hmm, we are having dwell issues also right now, and since we cant change out the ignition system mid-season, some tweaks is needed.

Do I understand correctly from the schematic, that current is limited by the op-amp(leads 8-9-10) that has - reference to the coil ground through a hi-po resistor R44?.
that gives the op-amp voltage reference linear to coil current. Now, to modify the 7amp limiter, all one needs to do, is tweak the same op-amp's positive reference (4 resistors). Also, it might be needed, to change the zener diode at the output to actually allow higher voltage there?

Thanks in advance.

 

[TurboBob]

the dwell time is limited by RPM.

To raise the limiting current, my first thought is to change the shunt resistor.

But, if dwell time is the issue, you need to get the coil to charge faster. The only ways to do that are use a different coil or raise the applied voltage.

Bob

 

[fog]

the dwell time is limited by RPM.

To raise the limiting current, my first thought is to change the shunt resistor.

But, if dwell time is the issue, you need to get the coil to charge faster. The only ways to do that are use a different coil or raise the applied voltage.

Bob

I dont read out from the shematic, how many ohms the shunt is.
Coil primary is 0.7 ohms?
full 14V loading, it would be close to 20 amps.

Now, if I wanted the spark energy to be as good as it is now in 6000 where it cuts out in 9000(the engine can go past 8000), then:
loading time right now: 3.33ms - off time 0.4ms = 2.93ms @ 7A
loading time at 9000: 2.22ms - 0.4ms = 1.62ms
amps should be 2.93 / 1.62 * 7 = 12.66A

Of course, dwell settings in bs3 should be reduced also, or the coils will not last.