Author Topic: Capacitor Discharge Ignition ?  (Read 3088 times)

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Offline MadMax

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Capacitor Discharge Ignition ?
« on: January 11, 2016, 02:30:58 am »
Hi, has anyone tried fitting Capacitor Discharge Ignition to there C10.
Kawasaki use to fit it to a lot of bikes years ago, but you hear little of it nowadays.
Now with CDI you got something like 350 volts pulse going across the coils, giving you  a mighty Big Spark.
 I remember rebuilding a number of Kawasaki H2 750 triple two stroke units years ago. Kawasaki was charging a small fortune for replacements on my side of the pond. About £180  ($310) each back then. (Their was one for each cylinder.)
So I took one apart only to find about 5 components if I remember right.
The high voltage on these came from extra windings on the alternator.
But some bikes had the high voltage generator part & discharge part in one box.
I wonder why it was dropped?   Reliability or the cost maybe. Who knows?
Has anyone experimented with them on the C10 or any other motorcycle?
This should get a few of the old brain cells moving. 

Offline mattchewn

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Re: Capacitor Discharge Ignition ?
« Reply #1 on: January 11, 2016, 02:37:00 am »
Max,
Stick coils allow simplicity and reliability as well as a hot spark.
Matt
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Offline MadMax

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Re: Capacitor Discharge Ignition ?
« Reply #2 on: January 11, 2016, 03:35:54 am »
Hi Matt, Yes you are right stick coils will give a better spark than standard,
I think that’s got to be one of the best mods going. But I bet you can’t open the plug gap to 0.25”or more and still get a fat spark. Or can you?
Now a combination of the two would give you one hell of a spark.
As we all know the bigger the spark the better the combustion. As proven with the earth mod some of you have done.
 Like I said before I was just wondering what happened to it & why you don’t see it any more?

Offline Bucky

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Re: Capacitor Discharge Ignition ?
« Reply #3 on: January 11, 2016, 10:54:54 am »
wondering what happened to it & why you don’t see it any more?


Some info on the whys

http://www.bing.com/search?q=capacative+vs+inductive+ignition&qs=n&form=QBLH&pq=capacative+vs+inductive+ignition&sc=0-26&sp=-1&sk=&cvid=FA68FFCAFB6348B1BA47165AF4A0DCA2

Not trying to be a wet blanket. I guess that just comes to me naturally.  :motonoises:


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Offline Bob H

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Re: Capacitor Discharge Ignition ?
« Reply #4 on: January 11, 2016, 11:43:23 am »
Has anyone actually measured the output of stick coils when retrofitted to a C10?   
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Offline Rev Ryder

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Re: Capacitor Discharge Ignition ?
« Reply #5 on: January 11, 2016, 12:31:53 pm »
Has anyone actually measured the output of stick coils when retrofitted to a C10?   
DING! DING!  DING! Good question.

Because they are wired in series, unlike on their source machines, it stands to reason they would have greatly reduced output due to the voltage drop across the circuit that HAS to happen.  So this has remained in the back of my mind since the beginning of their use, though everyone raves about easier starting, etc.  Inquiring minds are still inquiring. That's a good thing.  I do realize they work and C-10s run well with them. Just curious about true output and/or power increase/decrease.
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Offline Bob H

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Re: Capacitor Discharge Ignition ?
« Reply #6 on: January 11, 2016, 12:54:42 pm »
My suspicion, (NOT backed up by any measurements yet!) is that stick coils, when retrofitted to a C10 don't produce as good a spark as they could because they were designed to work with a much higher voltage pulse such as the C14 supplies.  The C10 ignition module is essentially an electronic set of points (switch) in the 12V whereas the C14 manual says it's pulse to the stick coils is 72V min.
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Offline GeorgeRYoung

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Re: Capacitor Discharge Ignition ?
« Reply #7 on: January 11, 2016, 01:19:56 pm »
. . . . Because they are wired in series, unlike on their source machines, it stands to reason they would have greatly reduced output due to the voltage drop across the circuit that HAS to happen.  So this has remained in the back of my mind since the beginning of their use, though everyone raves about easier starting, etc.  Inquiring minds are still inquiring. That's a good thing.  I do realize they work and C-10s run well with them. Just curious about true output and/or power increase/decrease.
Ah, thank you. Because our stock setup is a single coil feeding 2 cylinders, I've shied away from the Coil-Over-Plug conversion, as you have to stick two primaries in series, so each only gets 6 volts when it's designed for 12V. For the C10, it seems to be a solution in search of a problem.

Capacitor Discharge Ignition is beneficial in a two-stroke environment where the plug insulators are clogged with oily mung. It has a faster rise time which means that less energy is consumed in the mung and more energy is delivered to the spark, once it occurs.

Our C10 bikes have electronic ignitions, meaning that a semiconductor breaks the primary coil current, instead of crummy old mechanical points. Seems to work fine in many 4-stroke bikes and cars.


Offline RWulf

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Re: Capacitor Discharge Ignition ?
« Reply #8 on: January 11, 2016, 02:30:31 pm »
In an engine with somewhat correct air fuel, clean plugs and little oil in
the mix, once the combustion process is started with a spark, there is
no need to make the stark voltage higher. There is not much temperature
difference between a spark that will start the process and the voltage of
a much higher spark. Yes it may look bluer and brighter, the temperature
of the spark is the same. Even yellow sparks have the same temperature
they just don't have the same EMF (electromotive force). IN 2 strokes
the slow build up of a discharging coil allow some voltage to bleed off
thru the combustion gas. A capacitor discharge pulse like the pulse in
the C-14 has a virtual vertical leading edge. Very little time to bleed off.
Remember anymore than what is necessary to produce a reliable start to
the combustion is just a wasted money out of your pocket.

Offline JDM

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Re: Capacitor Discharge Ignition ?
« Reply #9 on: January 11, 2016, 02:31:26 pm »
. . . . Because they are wired in series, unlike on their source machines, it stands to reason they would have greatly reduced output due to the voltage drop across the circuit that HAS to happen.  So this has remained in the back of my mind since the beginning of their use, though everyone raves about easier starting, etc.  Inquiring minds are still inquiring. That's a good thing.  I do realize they work and C-10s run well with them. Just curious about true output and/or power increase/decrease.
Ah, thank you. Because our stock setup is a single coil feeding 2 cylinders, I've shied away from the Coil-Over-Plug conversion, as you have to stick two primaries in series, so each only gets 6 volts when it's designed for 12V. For the C10, it seems to be a solution in search of a problem.

Capacitor Discharge Ignition is beneficial in a two-stroke environment where the plug insulators are clogged with oily mung. It has a faster rise time which means that less energy is consumed in the mung and more energy is delivered to the spark, once it occurs.

Our C10 bikes have electronic ignitions, meaning that a semiconductor breaks the primary coil current, instead of crummy old mechanical points. Seems to work fine in many 4-stroke bikes and cars.
 
I am with you and Rev Ryder 100% when it comes to running stick coils on a C10. A few years ago, I was running stick coils on my C10 so I could carry a spare coil on long trips. Those stick coils are now hanging on my shop wall. I was on a long trip a few summers ago and was having trouble with the bike not wanting to start when the bike was hot. It would crank over just fine, but would not hit. I would have to get a jump start after a fuel stop. I had the battery checked and it showed it was good, but I still had to get a jump start almost every time I shut down. Every once in a while the bike would crank over just fine and start just as I would let off of the starter button. Remember now the bike would crank over just fine but would not start when it was hot. Finally one morning the bike failed to start when it was cold so we hooked up the jumper cables to get it to go. No amount of cranking would get it to fire up. I had to make a run to the closest town to purchase a new battery. This fixed the problem and I am still running that battery. I reinstalled to OEM coils. And, the stick coils are going to remain on the wall. If you are running stick coils, beware. AS I QUOTE, "it seems to be a solution in search of a problem." HTH JD 

Offline mattchewn

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Re: Capacitor Discharge Ignition ?
« Reply #10 on: January 11, 2016, 11:28:12 pm »
Here is a little info for all of you. Even a coil rated at 2,000,000 volts will NOT get anywhere near that to fire the spark plug.
The most (highest numerical number), voltage that will jump the spark plug gap is actually going to be the MINIMUM voltage required to actually be able to jump the gap. MAXIMUM VOLTAGE TO JUMP A SMALl PLUG GAP IS ONLY ABOUT 20,000 volts. This is an UNDER LOAD amount not an at idle amount. At idle a coil only needs to produce between 2K and 4K volts to fire the plug. This is why you got completely scammed when you bought those SUPER DUPER AWESOME gajillion volt coils for your hotrod! Your plugs did not see one volt more than the minimum required to fire the plug EVER!
Anyone that has ever used an ignition scope on a car can confirm this for you.   
Leaner fuel mixtures require more voltage to jump the spark across the gap than rich mixes do. the fuel reduces the "resistance" of the plug gap.

Think about water here for a second. pour water on the ground and watch where it goes. It will ALWAYS go the path of LEAST resistance. Electricity works the similarly. It also will only use the minimum required to do the "work".

A side note;  The "pulse" to the coil is not the supplied voltage. The supplied voltage is always what the alternator is putting out minus losses or adjustments made through resistors. It is a negative spike that actually causes the field to collapse generating the secondary voltage that fires the spark plug.

Just something to think about.

Stick coils are more efficient and easier to use in a "modular assembly" like an assembly line for engines. They also allow for ignition timing changes done via computer on a "per cylinder" basis instead of all or none methods.

I slept at a holiday inn express last nite!

Matt
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Offline GeorgeRYoung

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Re: Capacitor Discharge Ignition ?
« Reply #11 on: January 12, 2016, 12:43:28 am »
/Pedantry on/

. . . 
Leaner fuel mixtures require more voltage to jump the spark across the gap than rich mixes do. the fuel reduces the "resistance" of the plug gap.

As I understand it, the gap is made larger for lean mixtures, so there is more hope of something combustible being present. And therefore, the voltage requirement increases.

. . .
A side note;  The "pulse" to the coil is not the supplied voltage. The supplied voltage is always what the alternator is putting out minus losses or adjustments made through resistors. It is a negative spike that actually causes the field to collapse generating the secondary voltage that fires the spark plug.

That's true for our darling Kettering ignitions. For a Capacitor Discharge Ignition, voltage is accumulated on a capacitor (around 350V) and when it's connected to the coil, becomes the "supplied voltage".

/Pedantry off/

/Reminiscing on/

The '73 RD350 two-stroke I had was always fouling plugs. In an excellent series of articles in Cycle Magazine (now defunct), they measured the output of a number of motorcycle coils of the era, and found it was typically around 7000V. They measured automotive coils at more than 15000V.

Seven thousand volts is adequate to start and run when a plug is new, but after a few weeks of 2-stroke contamination, the thing would stop working. The solution for me was to buy two automotive coils, a couple of 1 ohm ballast resistors, and shoehorn everything under the tank. Even though it was still triggered by points, it worked like a charm for years, made fouled plugs a thing of the past. 15KV was always more than enough.

/Reminiscing off/


Offline mattchewn

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Re: Capacitor Discharge Ignition ?
« Reply #12 on: January 12, 2016, 01:01:08 am »
George,
The gap is made larger in order to increase the "needed" voltage to jump the gap. The leaner mix is aided by a longer/larger arc to ignite, hence the larger gap. On any give gap a leaner mix will require higher voltage to jump it.

The early coils didn't have a lot of high voltage potential in comparison to todays coils. Mid 70's GM HEI ignitions had 40,000-60,000 volts and more as a possible output although they never got that much to the plugs. The Olds Quad 4 had  4,  100,000 volt coils.  I think the C14 sticks are rated at 40k as well. pretty good for such a small package!
Matt


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Offline MadMax

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Re: Capacitor Discharge Ignition ?
« Reply #13 on: January 12, 2016, 03:37:36 am »
Well this topic has got the old brain cells moving.
I remember fitting an aftermarket CDI unit to a car that still used points years ago.
What a difference it made. I didn’t have to change down a gear to go up steep hills anymore.
The only problem came when it got damp, sparks everywhere. A new set of leads cured the problem.
 If I remember right I opened the plugs to 0.050”.

 Doesn’t the strength of the spark depend on the energy (joules) put in. ?

So putting  more energy in is going to give you a fatter spark.  It may only take say 20kv to jump say 0.025” But you need more to jump 0.05”
All I do know is it made a bug difference for whatever reason.
 
Aircraft Ignitors or “Cracker Boxes” for aircraft jet engines are similar to a CDI unit. But use one hell of a lot more energy.
  They use a very dangerous amount of energy to get a spark.  If you have ever stood near a  Jet engine on start up you can see why  the spark generator has got the name “Cracker Box”  Crack-Crack-Crack  until combustion takes place. But that’s another story.
One more thing came to mind. Why do some Drag Bikes use magnetos?
Maybe its to get a bigger spark?

Offline Rev Ryder

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Re: Capacitor Discharge Ignition ?
« Reply #14 on: January 12, 2016, 04:10:06 am »
A side note;  The "pulse" to the coil is not the supplied voltage. The supplied voltage is always what the alternator is putting out minus losses or adjustments made through resistors. It is a negative spike that actually causes the field to collapse generating the secondary voltage that fires the spark plug.

Agreed. Not so sure about "ground spike"... it's simply a breaking of the circuit by interrupting the ground.  However, placing 2 cop coils in series does produce a 50% reduction per coil of that supplied voltage.  The questions I had are, "How well does a 12 volt cop coil function when it is operating on 1/2 the design voltage?" How is the required dwell to meet saturation affected? Obviously the bikes start and run and folks seem to think they do everything better.  Is that really true? 
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Offline Bob H

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Re: Capacitor Discharge Ignition ?
« Reply #15 on: January 12, 2016, 11:56:10 am »
Till someone can find a schematic specifically for the C14 ECU module that drives the COP coils, we don't know for sure what they are designed for.  The C14 manual tests for a 72V minimum measured using the Kawasaki "peak voltage adapter".  Again, until someone can find out exactly what that does, we don't really know what the COP's on the C14 were designed for.  Unfortunately Kawasaki manuals typically don't include a "theory of operation" which some shop manuals do.

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Offline davida

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Re: Capacitor Discharge Ignition ?
« Reply #16 on: January 12, 2016, 01:43:33 pm »
This article covers more than i could possibly summarize...  But it seems like Steve's "more power mod" is the right answer .  a Coil relay would double down on feeding more power to the coils would improve output.   
http://www.motorcycleproject.com/text/high_perf_ignition_coils.html

George Young - I remember that article by Gordon Jennings.  What was lost is found! 
http://www.eurospares.com/graphics/engine/TheGreatIgnitionCoilTest.pdf
« Last Edit: January 12, 2016, 02:19:35 pm by davida »
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Offline RWulf

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Re: Capacitor Discharge Ignition ?
« Reply #17 on: January 12, 2016, 02:02:06 pm »
I believe your right. Jet fuel does not atomize like gas. You ready
have to add lot of heat to get it to start. Top fuelers are almost running
a liguid mixture in there cylinders. Look at the headers as they sit warming
up.
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Offline MadMax

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Re: Capacitor Discharge Ignition ?
« Reply #18 on: January 12, 2016, 04:22:35 pm »
Now as we all know the C 10 is an old bike. So is the ignition system.
 We also know the igniter box is basically an electronic switch. The switching is done by power transistors. Powers transistors 20 years ago do not have the capability of modern MOSFET type. Old type would maybe have a 1.5 ohm internal resistance when conducting. MOSFET maybe 0.015ohms or less.
So what you say. Well resistance means Heat and voltage drop.
 Not a good thing to have.
 If you was to put stick coils in parallel instead of series to give 12v to the coils instead of 6v the current would double.
 Which would means more heat & would cause the transistors to fail at some point.
So why not change the Output transistors to modern Mosfet type. 
Power = I ²x R. So lets say 2amps per coil is 2² x 1.5 = 6 watt per coil
Now 2amps² x 0.015= 0.06 watt. That a lot less heat and more voltage to the coils. The first would give a 3 volt drop and the second a 0.03 volt drop.
So has anyone opened up a igniter unit to repair one. It would be interesting to know what the O/P transistors  are ?  Then a modern alternative could be found.

Offline Bob H

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Re: Capacitor Discharge Ignition ?
« Reply #19 on: January 12, 2016, 04:26:35 pm »
First we need to know if increasing the voltage/current in the ignition coils will increase the output voltage.

I suspect that if the coils are saturating at their current design point, lowering the resistance of the igniter transistors may not have as much an effect as hoped.

These are questions, not answers!!!
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Offline mattchewn

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Re: Capacitor Discharge Ignition ?
« Reply #20 on: January 12, 2016, 04:35:08 pm »
First we need to know if increasing the voltage/current in the ignition coils will increase the output voltage.

I suspect that if the coils are saturating at their current design point, lowering the resistance of the igniter transistors may not have as much an effect as hoped.

These are questions, not answers!!!
Bob,
The coils are a voltage multiplier basically. Increase the voltage going in and it will have a corresponding increase in output. Coils have two sets of windings inside them. One set is on the primary side, this gets fed juice through the bikes electrical system once charged the voltage is cut off causing the electrical field of the voltage to collapse. this field collapses over the second set of windings and you get "inductive voltage" that goes to the plugs.  If the primary coil has one winding and it gets 10 volts lets say and the secondary winding has 100 windings then the voltage that would go to the plugs would be 1000 volts. (grossly simplified here) . That is (roughly) how it works though.
Got it?

Matt
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Offline Bob H

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Re: Capacitor Discharge Ignition ?
« Reply #21 on: January 12, 2016, 04:52:49 pm »
That's roughly how a transformer works, but the ignition coil is only sort of a transformer.  The high voltage in the secondary is caused by the sudden collapse of the induced magnetic field, and although the magnetic field is related to the number of turns in the primary, the induced voltage in the secondary is not specifically related to the turns ratio, but instead is a function of the magnetic field strength in the core, the collapse rate, and the number of turns in the secondary.

We are back to needing to know if the core is saturating, and what the relationship is between core magnetic field and primary current.
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Offline Bob H

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Re: Capacitor Discharge Ignition ?
« Reply #22 on: January 12, 2016, 05:04:55 pm »
I've got an opened igniter, looks like the switching devices are D7071, made by "EE"?  Don't recognize the company logo, I'll try to figure out who it is.
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Offline Zorlac

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Re: Capacitor Discharge Ignition ?
« Reply #23 on: January 12, 2016, 05:11:52 pm »
I reinstalled to OEM coils. And, the stick coils are going to remain on the wall. If you are running stick coils, beware. AS I QUOTE, "it seems to be a solution in search of a problem." HTH JD
Ahhh, doing nothing to my C10 (but ride) is vindicated again.  :rotflmao:
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Offline Bob H

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Re: Capacitor Discharge Ignition ?
« Reply #24 on: January 12, 2016, 05:17:55 pm »
I reinstalled to OEM coils. And, the stick coils are going to remain on the wall. If you are running stick coils, beware. AS I QUOTE, "it seems to be a solution in search of a problem." HTH JD
Ahhh, doing nothing to my C10 (but ride) is vindicated again.  :rotflmao:

Good answer!! :beerchug:
It's +2F here with snow blowing across the ice on the road, the bike landlocked in the garage, so I think I'll pass on riding today. :'(
Remember, much of what you see on-line is wrong or misguided, your task is to filter that out!
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