Question about ignition coils and resistance/application

[joedrum]

i cant beleave nobody has anything to say about this mod ....it seems to me to be the answer for all this discussion we are having

or im missing something ..... i think that im going to go this way on some of the project bikes im working on so to get common parts that one might need to keep these bikes going.....

it may take alittle trial and error to get everything right but im sure things are close enough to get there in my opinion.....

 

[dan filipi]

i cant beleave nobody has anything to say about this mod ....it seems to me to be the answer for all this discussion we are having

or im missing something ..... i think that im going to go this way on some of the project bikes im working on so to get common parts that one might need to keep these bikes going.....

it may take alittle trial and error to get everything right but im sure things are close enough to get there in my opinion.....

I want to put together a GM coil setup like that eventually.

Time and money.

 

[jdegase]

one thing to note on the GM mod. you would defiantly have to use the newer style wires and I might be concerned with the stock plugs. you could gap them to the GM spec. .42 I think.. the GM HEI (high energy ignition) should provide almost double the voltage to the spark plug.

also one other note.
a HEI ignition would have to pull more current on the primary side to support the higher output on the secondary side.
remember with a coil the windings multiply the voltage, but they divide the current. so they would draw more amps and the primary wiring might need to be modded slightly.

 

[dan filipi]

Good points Jim.

I wonder if the pickups or the wiring from them would be large enough, probably hah because thats on the trigger side of the modules, actual coil load is "switched" by the modules.

The Acell coils use I think a 8.8 MM silicone resistor wire. GM setup would probably something close to that. Would have to use non resistor plugs or whatever the GM setup calls for.
Aren't the Irridiums for our bike resistor? Would have to check the NGK site.

 

[Fewman]

Sooo...Dan, what has transpired? Have the $34 coils worked for your 1100?

I too have been unable to find an answer to a similar application question on coil resistance. I've read thru these posts and some on the NGW forum trying to better understand. I have a Prestolite ignition module that has worked well since 1978 (using stock '75 coils, with resistor, no condensers per Prestolite). I scored a set of Dyna 3ohm coils and have not heard anything definitive on the proverbial ballast resistor question? I'd like to install them!

My understanding is that a ballast is going to limit primary circuit voltage...for GL1000 stock system - coils (~1.6ohm) and ballast (3ohm) = ~5ohm. I think that results in lowering the voltage to about 2.7v, all to limit the breaker point arcing. I'm thinking that based upon the original Prestolite instructions (leave ballast in place and remove condensers), that the Prestolite EI was designed for ~2.7 volts. If I don't use the resistor w/dyna 3ohm coils, the primary circuit voltage would be around 4 volts. If this is all true, I guess the question is can the Presolite function at the slightly higher voltage. In your case, I wonder if the 1100 coil resistance is based upon the Honda EI module voltage requirements?

The only thing that doesn't make sense with my understanding is the Dyna instructions :read: for the 3ohm coils with stock breaker ignition is to leave the resistor in place. Again if I'm correct, that would limit primary voltage to about 2 volts. And then if you limit primary side voltage, won't that lower secondary side output and defeat the purpose of higher output coils. Boy am I confused now.... :head bang:

So do I use the ballast resistor or not? Any Sparky's out there for comment?

 

[dan filipi]

I never got those coils, got sidetracked.

joedrum knows quite a bit about the Dyna's.

Joe, you copy?

 

[Fewman]

Might be a little expensive but if I don't get any info soon, I think that I will just run without the ballast resistor. If the Prestolite fries, then I'll know it was a voltage issue and I'll get a Dyna S replacement. I know the Dyna S runs without the b/r when using their 3ohm coils.

Still would like to understand all this better...

 

[joedrum]

i realy dont know much about a prestolite ignition ....if it works on stock honda ignition ballist than its proably different than the dyna some ...as i remember it dynas came with there own ballist to replace the honda ballist ...on mime that ballist went bad ...wich led to buying 3ohm dyna coils with no ballist ....it would be somwhat a gamble on the dyna coils and prestolite ignition .....but if i had them in my hand i couldnt not try it .....getting rid of the ballist is a huge mod in my book all that heat around the coils ,every wire on the the bike it seems and they just do go bad .....if in the the end it torches your prestolite you can replace it with the dyna and have a perfectly matched ignition system .....one of the best things i did to the 79 1000 among many .....hotter spark ,wakes a wing up and the 3ohm coils is the biggest part of improvement in the better spark......new wires caps and such are a given to do also...... :mrgreen:

 

[scdmarx]

I would leave the resistor in the primary side. It's purpose is to limit current flow in the primary circuitry. In an electronic ignition, transisters are electronically controlled "on-off" switches that replace the mechanical "on-off" switching function the tungstin points used to do. Transisters are manufactured to safely handle "x" amount of current for a given amount of time. Unless you know the specs, you'd PROBABLY do well to err on the side of safety.

This is the first time I've seen this topic. I don't have all the answers. But I do find it some interesting reading. I have some personal brain fodder I'd like to toss into the mix. First, I'm thinking that the resistance in the primary side of the coil, may have something to do with primary saturation time, and in relation to the secondary resistance, coil secondary output. But I could be wrong about that. It's just something that's making me go "hmmmm". When the primary circuit is switched on, current flows through the primary winding of the coil, saturating it with available voltage. It's been a few years since I've seen this drawn out on a chalkboard, but I'll try to speak my mind and anyone can jump in. As current flows through a wire, it creates a magnetic field. When it flows through a coiled wire that magnetism is concentrated. AND... when you pass a magnetic field over a completed circuit it induces the flow of electrons. In an ignition coil, when the primary circuit is switched off, the magnetic field collapses, inducing a voltage in the secondary circuit. Just how much induced voltage is available as the result may have something to do with the resistance in the secondary winding, as well as the amount of saturation in the primary circuit. (gotta have something to work with)
The higher the RPM, the less "time" the primary has to become fully saturated. So then, how quickly this coil primary winding can saturate, and how much heat this unit can tollerate over a period of time, I'd imagine all has to do with the engineering design and manufacturing process. So in my ignorance, if I had to make a decision, I'd choose the coil with the closest primary resistance to the original equipment. Now for the secondary circuit, which is isolated from the primary circuit, it is capable of producing several thousands of volts. But the circuit will only use as much as it takes to overcome the largst resistance in that circuit. Ideally, that will be the spark plug gap. In the '80's we saw some pretty large plug gaps. Some as much as .080" but most were .045" to .060". The reason for these large gaps was to try to ignite the lean air/fuel mixture in a scramble to meet mandated EPA requirements. (leaner is harder to ignite because air is an insulator and there are fewer gasoline molecules to bridge the spark plug gap to allow current to flow.) The result was that the spark plug electrodes were burning down creating an even larger gap, requiring more voltage/current flow, which would start burning the plug wire connections, requiring even more voltage/current, which would start burning through the coil tower in the distributor cap. Tune ups could get expensive. Then Cadillac made a car that required engine removal to change that one spark plug in the back. So they then invented a spark plug that was supposed to last a hundred thousand miles.
Sorry for the rabbit trail. :blush:
Anyways, the secondary circuit will only use what voltage it takes to push current through the highest resistance in that entire circuit. (hopefully the spark plug gap) So something running pump gas with a plug gap of .030" I don't think is gonna require all that much. And it should be capable of saturating the primary winding @8,000 RPM if that's the way you intend to run it. :hihihi:

 

[aslatk]

I would leave the resistor in the primary side. It's purpose is to limit current flow in the primary circuitry. In an electronic ignition, transisters are electronically controlled "on-off" switches that replace the mechanical "on-off" switching function the tungstin points used to do. Transisters are manufactured to safely handle "x" amount of current for a given amount of time. Unless you know the specs, you'd PROBABLY do well to err on the side of safety.

This is the first time I've seen this topic. I don't have all the answers. But I do find it some interesting reading. I have some personal brain fodder I'd like to toss into the mix. First, I'm thinking that the resistance in the primary side of the coil, may have something to do with primary saturation time, and in relation to the secondary resistance, coil secondary output. But I could be wrong about that. It's just something that's making me go "hmmmm". When the primary circuit is switched on, current flows through the primary winding of the coil, saturating it with available voltage. It's been a few years since I've seen this drawn out on a chalkboard, but I'll try to speak my mind and anyone can jump in. As current flows through a wire, it creates a magnetic field. When it flows through a coiled wire that magnetism is concentrated. AND... when you pass a magnetic field over a completed circuit it induces the flow of electrons. In an ignition coil, when the primary circuit is switched off, the magnetic field collapses, inducing a voltage in the secondary circuit. Just how much induced voltage is available as the result may have something to do with the resistance in the secondary winding, as well as the amount of saturation in the primary circuit. (gotta have something to work with)
The higher the RPM, the less "time" the primary has to become fully saturated. So then, how quickly this coil primary winding can saturate, and how much heat this unit can tollerate over a period of time, I'd imagine all has to do with the engineering design and manufacturing process. So in my ignorance, if I had to make a decision, I'd choose the coil with the closest primary resistance to the original equipment. Now for the secondary circuit, which is isolated from the primary circuit, it is capable of producing several thousands of volts. But the circuit will only use as much as it takes to overcome the largst resistance in that circuit. Ideally, that will be the spark plug gap. In the '80's we saw some pretty large plug gaps. Some as much as .080" but most were .045" to .060". The reason for these large gaps was to try to ignite the lean air/fuel mixture in a scramble to meet mandated EPA requirements. (leaner is harder to ignite because air is an insulator and there are fewer gasoline molecules to bridge the spark plug gap to allow current to flow.) The result was that the spark plug electrodes were burning down creating an even larger gap, requiring more voltage/current flow, which would start burning the plug wire connections, requiring even more voltage/current, which would start burning through the coil tower in the distributor cap. Tune ups could get expensive. Then Cadillac made a car that required engine removal to change that one spark plug in the back. So they then invented a spark plug that was supposed to last a hundred thousand miles.
Sorry for the rabbit trail. :blush:
Anyways, the secondary circuit will only use what voltage it takes to push current through the highest resistance in that entire circuit. (hopefully the spark plug gap) So something running pump gas with a plug gap of .030" I don't think is gonna require all that much. And it should be capable of saturating the primary winding @8,000 RPM if that's the way you intend to run it. :hihihi:

Boy you did a good job explaining that! Have you taught the engine performance aspect of automotive? First time tonight I've read this thread. Interesting. Only thing I'm going to add is that the plugs usually take 7 to 10 kV to fire. Old fashion ignition coils use to put out about 25 to 30 kV. GM's HEI ignition puts out 50 kV plus so you have plenty of reserve either or. Yes, required voltage goes up under a load but if you have a good stock ignition, you still should have plenty of reserve. On my 80 wing the plug gaps are 024" to 028" (pretty small). Found out the bike runs better with a plug gap of .032 which requires a little bit more voltage to fire which means a hotter spark. It really did make a difference. If I recall correctly, there is a change from 80 to 81 year model. Ballist is external on 80 and earlier and I think 1981 the ballist resiatance was built into the coils (maybe this was discussed already or irrelevant). Scdmarx...You know JStokes?

 

[slabghost]

If in doubt run the ballast resistor.

 

[scdmarx]

[Boy you did a good job explaining that! Have you taught the engine performance aspect of automotive? First time tonight I've read this thread. Interesting. Only thing I'm going to add is that the plugs usually take 7 to 10 kV to fire. Old fashion ignition coils use to put out about 25 to 30 kV. GM's HEI ignition puts out 50 kV plus so you have plenty of reserve either or. Yes, required voltage goes up under a load but if you have a good stock ignition, you still should have plenty of reserve. On my 80 wing the plug gaps are 024" to 028" (pretty small). Found out the bike runs better with a plug gap of .032 which requires a little bit more voltage to fire which means a hotter spark. It really did make a difference. If I recall correctly, there is a change from 80 to 81 year model. Ballist is external on 80 and earlier and I think 1981 the ballist resiatance was built into the coils (maybe this was discussed already or irrelevant). Scdmarx...You know JStokes?

I have noticed very much easier starting of my Interstate when the motor is cold ever since I've been leaving it on the battery tender overnight. Acts like a completely different bike. So I'd have to agree that having that available voltage there helps. And I can't help but think that gasoline today is a lot more different than the gasoline we bought 30 years ago.

I haven't taught any automotive, but I've sat through countless hours of it since i was sixteen. :heat: There has been a lot of info pass through my noggin, and what little has been retained is more jumbled and hard to sort through the older I get.

JStokes? Is he that preacher guy on tv? :nea:

 

[Fewman]

Thanks for the info SCDMARX. Much appreciated.

So one question... is my assumption (below) about the lower primary voltage accurate with the 3ohm value of the coil resistance in the primary circuit (being 4v)? Another point (now I'm being dangerous :music: ), if the primary side starting voltage is momentarily higher during cranking (ballast is bypassed), then the Prestolite may indeed withstand the slightly higher 4 volts continuous. Thoughts...

the Prestolite EI was designed for ~2.7 volts. If I don't use the resistor w/dyna 3ohm coils, the primary circuit voltage would be around 4 volts.

 

[dan filipi]

To throw a little loop into things, I have a old 1100 ballast when connected to no load I get 11 volts through it from a 12.8 volt battery.
Being no load voltage maybe doesn't tell us anything, would need to be connected to the coils for any worthwhile information?

if the primary side starting voltage is momentarily higher during cranking (ballast is bypassed), then the Prestolite may indeed withstand the slightly higher 4 volts continuous. Thoughts...

That's only intended to be momentary I think.
The reason being is the hotter primary is needed because the starter load lowers battery voltage.
Without the bypass may be way too low to produce a spark.

I had a Dodge that had the resistor go bad. It would start when cranking but die as soon as the starter was let go at the key. I couldn't find the ballast resistor right away and had to get to work so I ran an ignition wire straight to the coils. That coil got HOT! I'm sure it would not have lasted very long.
When I got home I found the resistor and put it back.

 

[slabghost]

It's your bike,your dime, and your risk. I'm no expert but if memory serves back in the day the ballast resistor was on cars with points ignition to halve the operating voltage and reduce burning of the points. Some systems had 6 Volt coils that recieved 12 volts for starting. Personally if it runs good with the ballast resistor I'd leave it.

 

[scdmarx]

To throw a little loop into things, I have a old 1100 ballast when connected to no load I get 11 volts through it from a 12.8 volt battery.
Being no load voltage maybe doesn't tell us anything, would need to be connected to the coils for any worthwhile information?

True, it will create a voltage drop. But the purpose is more for ballast to act as a current limiter.
Ballasts change resistance with current as they heat and cool, and thus provide a sort of buffer for the coil. Coil current will be different at higher and lower RPM.
You're an electrician, so you understand the difference between voltage and current.
The ballast reduces the current flow thru the coil at low speeds and keeps the coil from overheating. As you said the coil can handle more amperage but not for long periods of time. So at idle and low engine speeds the points have more time to be closed and thus the current heats the ballast up and causes it to have more resistance and drop current flow at lower engine speeds when full coil output is not needed. When you go faster and speed the engine up the points have less time to be closed so the ballast cools down some and the resistance drop causes more current to flow thru the coil and letting the coil output higher when it is needed at higher engine speeds. And when cranking the ignition system needs full output to help start the engine so the ignition switch bypases the ballast and gives full battery volts to the coil while cranking.
While you could do a quick voltmeter-ohmmeter static test to see if the part is any good (go-no go) and for the most part seldom have any reason to go any further than this, the real concern here would be best measured with a ammeter while the system is running.
These days, between modern coils and computer controlled ignition systems, I hardly ever see a ballast resister anymore. You made me go through some old boxes to dig this stuff up. :thanks:

 

[joedrum]

again ron explains it so well ...i can realy understand it ..... :music: :shock: :mrgreen:

 

[Fewman]

Well guys, I'm goin' for it... :beg: ...no ballast, dyna coils, prestolite EI. :swoon:

It's been 3 years since this ride last seen pavement (myself included) and I finally have everything back together (new head gaskets, de-rusted tank, Randakk carb rebuild, FH012 regulator, belts, rad hoses, rebuilt brakes & hoses, some new wiring/fuses at battery, and lots of nickel/dime tinkering). I plan on start-up later this week, weather permitting here in the high Rockies, as I think it's safest done outdoors :music: ....and it's gonna smoke :heat: !! I'll let you know if there's any more smoke than what's comin' out the exhaust...

 

[dan filipi]

I'm curious how that FH012 regulator is working out for you.
Not many have done it yet so I'd like to know if the mod is worth the cost.

 

[joedrum]

just nice job ...i think getting things done and such ....cant wait to hear about the ride popcorn