Topic: Ignition coils: 3Ohm vs 5Ohm: What's the difference?

[roach374]

Sorry if this is a noob question. I tried googling this, and all I get are videos talking about how to use an ohmmeter to tell what coils you have. I know what coils I have (5 Ohm). What I want to know is: What's the difference?

In my simplified mental model of how coils work, they are basically always charging (from the battery / stator), then discharging (via the plugs) based on timing dictated by the points. Where does the Ohm rating enter into it? What's the functional difference between 3ohm and 5ohm (other than the obvious one, resistance)? How do I know if I have the "right" coils?

[Bankerdanny]

Ohms are a measure of resistance, smaller number = less resistance to the flow of current.

Generally speaking the 3ohm coil will allow more power to be stored in the coil at the price of greater draw on the charging system. Theoretically a lower ohm coil will produce a stronger spark. That said, the use of points limits the ability of the ignition system to take advantage of the extra power.

I know plenty of guys here that run a 3phm coil without issue and others that will recommend adding a secondary resistor to the system to raise resistance back up to the stock 5ohm level. On a basically stock bike I would stick with 5ohm coils.

[roach374]

At last! An explanation that makes sense! Thank you!

[HondaMan]

There is one important item for these bikes that is not mentioned in conventional coil conversations: the lower the primary resistance of the coil, the shorter the spark DURATION when it occurs. These engines desire a LONGER spark, not a HOTTER one: they will run perfectly with spark voltages as low as 4500 volts (by actual measurement in my shop days), and the stock coils are more than 7000 volts.

Also: not even the 750 alternator can support the 3-ohm coils on these bikes without serious troubles showing up, eventually. Use 4 to 5 ohm primary coils on these bikes to save yourself a lot of grief! The OEM coils on the 750 were 4.5-4.6 ohm primary until 1975, then 4.3-4.4 ohms. All of the other Fours with points used the 4.3-4.4 ohm versions from day one.

[dave500]

ill be in trouble with my daisy chained 0.4 ohm coils then?

[Korven]

There is one important item for these bikes that is not mentioned in conventional coil conversations: the lower the primary resistance of the coil, the shorter the spark DURATION when it occurs. These engines desire a LONGER spark, not a HOTTER one: they will run perfectly with spark voltages as low as 4500 volts (by actual measurement in my shop days), and the stock coils are more than 7000 volts.

Also: not even the 750 alternator can support the 3-ohm coils on these bikes without serious troubles showing up, eventually. Use 4 to 5 ohm primary coils on these bikes to save yourself a lot of grief! The OEM coils on the 750 were 4.5-4.6 ohm primary until 1975, then 4.3-4.4 ohms. All of the other Fours with points used the 4.3-4.4 ohm versions from day one.

Im having a hard time to grab my head around the LONGER spark vs HOTTER spark. Does the longer spark, weaker spark ignite more efficient than the shorter, faster spark? Would a combination of the two provide the better ignition? I thought that one of the main reasons why transistorised ignitions exist is that the extremly fast trigging (~ns) causes a sharper discharge in a smaller timeframe? Is it so that the exploding gases are so much slower at igniting the remaing gas providing some sort of lag?

[dave500]

dont read too much into it korven,just be sure your ignition is set up correctly and itll be fine,invest in a decent electronic unit and make it better,in the day the tech was too exxy and unreliable,transistor radios and colour tv was new!even the kick start was retained as electric start was sort of new on bikes and not really trusted then,dont over think the #$%*,youll have sleepless nights!

[dave500]

some coil and ignition makers would almost have you believe the engine can run on the spark alone?

[Deltarider]

In spite of multiple requests, nobody has shown any proof of this claimed longer or shorter spark so far. That is a bit strange. An oscilloscope is all what it takes. Do tests and convince us when you can demonstrate a significant difference in burn time expressed in µseconds.
Here's what I know for a fact (which is not much ).
Decades ago I was ignorant and bought 3Ω (Dyna) coils. Well, you don't need those and I join others here in recommending to stick with the standard value of around 4,7Ω coils. However... never ever have I experienced less (or more, for that matter) performance with forsaid 3Ω coils and, boy, have I experimented! So, compared to the standard value coils, I found no improvement, but also no downturn. I've fitted them with and without a ballast resistor. Furthermore I have compared the current of both 3Ω coils and 4,7 Ω coils with the engine running and surprise, surprise, the difference was very little indeed and certainly less than others here have predicted citing Ohm's law. You don't have to believe me, you can carry out the tests I did yourself and that is more than others here offer. Then, ask yourself: how many times have you read here or anywhere: "Wow, what a difference when I changed the 3Ω coils for 4,7 coils!" Or: "Wow, what a difference it made when I changed the 5kΩ for 10kΩ  plugcaps!"
Yes, my 3Ω coils draw a little bit more current. But how much of that energy is transformed into heat and how much into spark energy is anybody's guess. Again I have experienced no gain, but also no downturn.
So after all my testing, it is only fair, that when somebody claims a significant difference, I'd like to see data. May I suggest a scope image?
For the last 30 years I have run my CB500 with my homemade transistor ignition that itself also draws some extra current. My bike came with a 55/60 Watts halogen. With a conventional lead acid battery, all my rides ended in a better charged battery than I took off with. I have not changed any of the electronic components. Regulator, rectifier are the same that were on the bike when it left the assembly line. Apart from my EI, the most 'sophisticated' part on my bike is that dumb diode that prevents starting when in gear. In Europe we don't have that silly 'headlamp always on' arrangement.
When I calculate what I can reach just by walking or cycling and compare it to riding the bike, such a ride has to be at least 25 mins to make good for time lost in: dressing up, earplugs, helmet, gloves, opening the garage and maybe even a stop at a gas station. I have several riders reports in my archives published in the 70s and 80s, put together by hundreds of CB500/550 riders. Nobody had complaints about the charging system. So this so called poor charging system is, in my opinion, just BS and I wish it would end. Too many here have been infected by this virus already.

[69cb750]

In spite of multiple requests, nobody has shown any proof of this claimed longer or shorter spark so far. That is a bit strange. An oscilloscope is all what it takes. Do tests and see if there is a significant difference in burn time expressed in µseconds.

The coil voltage starts at zero volts, rises to several thousand over a short period of time then decreases back to zero.
This happens so fast your eye and brain cannot see it.
Some oscilloscope have a capture and reply feature so you can see the curve and features of it.

[69cb750]

[69cb750]

[ckahleer]

When we ohm out a coil, we are measuring straight line DC resistance. During operation, coil current is constantly starting and stopping many times a second. This brings inductive reactance into play. The higher the frequency (RPM), the greater the reactance. A 3 ohm coil could actual draw less current then a 5 ohm coil, depending on the inductance of the coils. Inductance is like inertia. There is more resistance to getting electricity moving than to keep it moving.

[HondaMan]

ill be in trouble with my daisy chained 0.4 ohm coils then?

Are they really 0.4 ohms? They won't even run with points, if they are. The points won't last but a few minutes, tops, if it runs at all. Normally the less-than-2.5 ohm coils are made for CDI or ECM-driven systems, where the spark is created 'backward' from ours, so to speak: the power is sent thru the coil at the moment of spark and they generate HV pulse then, discharging quietly afterward. The Kettering design on our bikes charges the coil up for a 'dwell' period, then stops suddenly to let the coil's magnetic field collapse and make the spark.

[HondaMan]

There is one important item for these bikes that is not mentioned in conventional coil conversations: the lower the primary resistance of the coil, the shorter the spark DURATION when it occurs. These engines desire a LONGER spark, not a HOTTER one: they will run perfectly with spark voltages as low as 4500 volts (by actual measurement in my shop days), and the stock coils are more than 7000 volts.

Also: not even the 750 alternator can support the 3-ohm coils on these bikes without serious troubles showing up, eventually. Use 4 to 5 ohm primary coils on these bikes to save yourself a lot of grief! The OEM coils on the 750 were 4.5-4.6 ohm primary until 1975, then 4.3-4.4 ohms. All of the other Fours with points used the 4.3-4.4 ohm versions from day one.

Im having a hard time to grab my head around the LONGER spark vs HOTTER spark. Does the longer spark, weaker spark ignite more efficient than the shorter, faster spark? Would a combination of the two provide the better ignition? I thought that one of the main reasons why transistorised ignitions exist is that the extremly fast trigging (~ns) causes a sharper discharge in a smaller timeframe? Is it so that the exploding gases are so much slower at igniting the remaing gas providing some sort of lag?

The amount (or type) of spark that is needed is determined by the engine's design, in most cases (and certainly in our situation). The Honda engine of the pre-1990s era was designed around a swirl-charge inside the chamber (at least in these Fours) at a 9:1 effective compression ratio (200 PSI top pressure before combustion). With a long-duration spark, the gases are swirling past the sparkplug tip and get ignited in a wide arc. With a short-duration spark in these engines, less of the mixture gets 'lit', so there is more unburned fuel at the end of power stroke, which translates to less torque (and more emissions, if you care) and often, yellowed header pipes. The longer the spark duration, the better the burn. These engines only need 4500 volts of spark: any more than that is wasted. The OEM coils are 7500 volts of spark.

[PeWe]

Coils to be adapted to the ignition used and bike.

I put a Dyna-S on my CB750 with Dyna 3 ohm coils. Battery drained really quick after a test ride of 50km, half way no headlight on to save juice. It was just it could start on the starter when back home. I realized quickly why thanks to this forum where this has been discussed.
Rpm was over 5000  most of the time.

Went back to the seller and traded coils in to Dyna 5 ohm.  Problem solved.

After that back to points and Hondaman ign module. I had read too many posts about sudden not working Dyna- S ignitions. .
Usually 2:3 that gives up. Maybe can't cope with temp or overcharging.

[dave500]

boy you guys gotta get out the dark ages,just use a proper modern electronic ignition,dynas are trouble all over any forum,imagine if you swapped into any of the new cars these days a kettering points system?im not one for full on sensors and injection etc but the old points can take a rest,modern ignitions really transform these bikes and any old cars etc.

[PeWe]

Which ignition will work fine and can be trusted on a CB street bike ridden on remote roads far from home or a workshop?

Overcharging should not be a problem either. Stock alternator able to feed ignition and daylight headlight on as well.

Modern bikes have much more juice from their charging systems to be used on ignition and fuel injection.

A race bike is seldom far away from a toolbox and truck. Battery fine without charging during the short ride.

[dave500]

all those questions relate to any old bike,dynas seem to have problems?im sure half of are installer dumbarse error?a lot of #$%*witts tamper with these bikes,update to electronic regulator aswell,one thing follows the other.

[rotortiller]

I am amused at some of the wet and brown being thrown around. Points or electronic, the bike will and does work fine with both. The electronic will be more precise and longer lasting when built and installed correctly. Any time you use contact switching there will be wear and tear. Like  unreliable points brands there will be crap  electronic ignitions too,  in some cases we have the opportunity to combine both LOL. How many dirt bikes are running remote areas with electronic ignitions? Most all of them.

Dark ages abound and totally agree for those residing there,  I say bring back the vacuum tubes, they are immune to EMPs! While they are at it lets do  8-tracks and CRTs.

Short duration high voltage spark or CDI seems to do fine, better  in oil laden cylinders with less than ideal combustion conditions. Old farts love to swirl old #$%*, it's a way of preserving history and feeling young, locked in and totally committed to the past. Nothing wrong with that either,  however the BS seems to be tossed more than sparingly. LOL

[PeWe]

The interesting thing is good ignitions for these CB Fours.
 (With their charging limitations,  relatively low power output)

I guess we all know that modern ignitions for modern cars and bikes are very good, seldom fail with no need of service since 30 years back.

Our bikes design are from the 60's, probably older

My car is manufactured late 2003 and work fine after free replacement of 4 crappy stock coils when broke after a few years as thousands of other cars from VW-Audi-Seat (VAG), all shipped with low quality stuff for around 10 years.

If a new R1 or similar bikes have a perfect ignition does not help our old Honda 4s.

That's why I wrote the question. It is very interesting to read  success stories about ignitions to these old bikes and how to get there with reliability.

Maybe frequent check of charging and max voltage is one thing?

EDIT: I have read threads about this before.
Today years after discussions about PAMCO (with  Ultimate 2.5 ohm coils)
vs Dyna-S/III/2000 (3 or 5 ohm coils)
vs Hondaman ign module
vs old Boyer
vs new China Dyna-S look a like .....
and more ?


Do these still work as seen and expected 5-10 years ago?
Which is the "winner" today?

[Deltarider]

For those of you who are interested in facts - that can be checked - rather than projections, a Dutch engineer has tested and evaluated some aftermarket electronic ignitions. He did this for a club of vintage MG sports car owners. The results are also useful for us. Among the ignitions tested was the Velleman K2543 kit, that I personally have experience with. Decades ago I boldly copied Vellemans design -  somewhat modifying it - for my homemade transistor ignition. This module has been on my bike for the last 25-30 years and has proved very reliable indeed. Now not all products in the test are available worldwide, so I limit myself to forsaid Velleman kit.
Have a look at the pic below if you like. What we see is a rise time much shorter thanks to the transistor that switches way faster than conventional breakerpoints ever can. Because there is still a 0,22µF condenser in the scheme, rise time is still a 20µs. Other products may offer an even shorter rise time, but 20µs to reach maximum spark voltage, is good enough. You may remember Velleman uses the breakerpoints to switch the control current. These points will now live almost for ever. Mine approach 60.000 kms. You could leave out Vellemans condenser to shorten the rise time even further, but than you may run the risk there will be extra firing in the event breakerpoints would bounce. So I prefer to keep that condenser in the module to smooth out or 'extinguish' so to speak unwanted extra firings. In such an event an electronic tach/dwellmeter would immediately show funny readings ofcourse and I prefer to be able to check dwell and tach from time to time.

[Deltarider]

Now the burn time. In the test the Velleman generated a burn time of 2500µs (Bosch 3Ω coil). Well, a fat 2ms burn time is just excellent. In the test, burn time extended over 36^o @ 3000 rpm. What more could you want?
Some of you don't want breakerpoints at all. OK, but than the product must be very reliable. My module never failed and in the event it would, I can return to standard within a few minutes.
Moreover I must confess I'm not impressed by some aftermarket products. I'd rather not have electronic components behind the points cover. The Tytronic may be OK, at least, has my benefit of the doubt, because the manufacturer was wise enough to limit the duty cycle to 50%. One of the most expensive products is the Boyer & Bransden. Personally I fail to understand why all four plugs should fire at the same time. In my judgement that is even cheaper to make, but that's just me. I have no experience with their product, but it seems to me that extra erosion at the sparkplug electrodes is to be expected. What I know well is that there is a lot of stuff you can sell to people with invisible ‘mysteries’ like electricketry and magnetism.
Finally, I cannot accept responsability for the data shown, for the simple reason that not I but somebody else has carried out the test. But... for the sanity of this forum I would like that, who ever states something about phenomena like spark duration etc, from now on will have his or her claim accompanied by facts, that any of us can check.

[2wheels]

Delta.  Can you explain burn time.  I see the initial voltage spike.  Then a little ringing.  Then the 2.? Milliseconds where the voltage remains at 26 volts.  Why does the voltage do this, why is that burn time.

Also i am guessing they are measuring the voltage at the output of the coil and using a 10:1 probe so that 280 volt pulse is 2800 volts and the 26 v is 260 volts.  But i am not sure.

[PeWe]

I remember Vellemann electronic kits building things. I made a preamplifier and a RIAA module 1978-79 for my stereo. Today is a 6.1 home cinema system for +30.000 euro nothing special.

This module is something like Hondaman's module, right?

I have capacitors 0.22 uF/630V to replace the stock condensers.
 
I have not done that yet. Planned to sit outside engine, halfway to the Hondaman module.

[Deltarider]

Delta.  Can you explain burn time.  I see the initial voltage spike.  Then a little ringing.  Then the 2.? Milliseconds where the voltage remains at 26 volts.  Why does the voltage do this, why is that burn time.

What you see in the graph, is what is happening in the coil's primary. But it represents also what's happening simultaneously in the secundary circuit/between the sparkplugs electrodes. In principle the voltages shown in the primary circuit are multiplied by the winding ratio. IIRC the CB750 coil's primary circuit has 380 and the secundary 15000 windings. That makes a ratio of say 1:40. As a rule of thumb the voltages shown in the primary can then be multiplied by 40 if it happened to be your coil. So this gives you some idea of the voltages at the sparkplug. But... let's not concentrate on voltages. What is delivered between the sparkplugs electrodes is energy or better said: heat which is normally expressed in (milli)Joules. The voltage is just a way of looking at the phenomenon and quite frankly, I don't find it very meaningful but we can use it. Anyway, the initial high peak is the voltage needed to ionize the air/fuel mix between the electrodes, to become conductive. As soon as the spark starts, voltage drops dramatically to a level where we nonetheless still have a period where arcing takes place between the electrodes. That is the socalled burn time. If, for whatever reason, the initial peak was not sufficient to start the flamefront travelling through the combustion chamber, the burn time helps completing this. Think of a very energetic zig zag saw like activity in arcing going on. Overthink this in slow motion and you will get the picture.
A few things to bear in mind. The sparkplug has only two duties: A. To ignite just a tiny bit of mixture around its electrodes and B to stay clean, so it can continue to do A. Let's look at A. As soon as the plug has succesfully performed duty A, the created flamefront in principle will take care of the rest of the combustion. That's the idea. Again, overthink the action in slowmo and you will understand. To resume, you need a relative high peak to establish a spark and then a period of time the electrodes are still arcing to deliver all in all sufficient heat. The voltage is dependent on 1. the electrode gap's wideness and 2. the conditions in the combustion chamber. The latter varies very much with load/rpm but also with other conditions like (partly) fouled sparkplugs and the presence (or not) of carbon deposits in the combustion chamber. Please do not forget the combustion engine is a very primitive machine and in evolution only the next step after the steam engine. On a steamlocomotive you had the driver (engineer) and the stoker. From time to time the stoker would open a lid to add coal to a fire already in process. New with the arrival of the combustion engine was that we now put in the fuel first and then let the sparkplug strike a match. I agree, it is ridiculously outdated and, given that only some 20% of the energy is transformed into motion and the rest is lost in heat, such a machine should have been phased out long time ago. Yes, we all are riding old stinking furnaces.
Let's focus a bit on the rise time. The shorter that time, the less the ignition will suffer from parasitic drain. Parasitic drain is caused by old, (partly) fouled or even wet sparkplugs and/or detoriated plugcaps and/or old high tension cables. CDI systems clearly have the advantage here. Rise time with a CDI is extremely short, but the concept also has disadvantages: no burn time to mention one .

[Korven]

Delta.  Can you explain burn time.  I see the initial voltage spike.  Then a little ringing.  Then the 2.? Milliseconds where the voltage remains at 26 volts.  Why does the voltage do this, why is that burn time.

What you see in the graph, is what is happening in the coil's primary. But it represents also what's happening simultaneously in the secundary circuit/between the sparkplugs electrodes. In principle the voltages shown in the primary circuit are multiplied by the winding ratio. IIRC the CB750 coil's primary circuit has 380 and the secundary 15000 windings. That makes a ratio of say 1:40. As a rule of thumb the voltages shown in the primary can then be multiplied by 40 if it happened to be your coil and you will have an idea of the voltages at the sparkplug. But... let's not concentrate on voltages. What is delivered between the sparkplugs electrodes is energy or better said: heat which is normally expressed in (milli)Joules. The voltage is just a way of looking at the phenomenon and quite frankly, I don't find it very meaningful but we can use it. Anyway, the initial high peak is the voltage needed to ionize the air/fuel mix between the electrodes, to become conductive. As soon as the spark starts, voltage drops dramatically to a level where we nonetheless still have a period where arcing takes place between the electrodes. That is the socalled burn time. If, for whatever reason, the initial peak was not sufficient to start the flamefront travelling through the combustion chamber, the burn time helps completing this. Think of a very energetic zig zag saw like activity in arcing going on. Think slow motion.
A few things to bear in mind. The sparkplug has only two duties: A. To ignite just a tiny bit of mixture around its electrodes and B to stay clean, so it can continue to do A. Let's look at A. As soon as the plug has succesfully performed duty A, the created flamefront in principle will take care of the rest of the combustion. That's the idea. Again, think slowmo and you will understand. To resume, you need a relative high peak to establish a spark and then a period of time the electrodes are still arcing to deliver all in all sufficient heat. The voltage is dependent on 1. the electrode gap's wideness and 2. the conditions in the combustion chamber. The latter varies very much with load/rpm but also with other conditions like partly dirty sparkplugs and the presence (or not) of carbon deposits in the combustion chamber. Please do not forget the combustion engine is a very primitive machine and in evolution only the next step after the steam engine. On a steamtrain you had the driver (engineer) and the stoker. From time to time the stoker would open a lid to add coal to a fire already in process. New with the arrival of the combustion engine was that we now put in the fuel first and then let the sparkplug strike a match. I agree, it is ridiculously outdated and, given that only some 20% of the energy is transformed into motion and the rest is lost in heat, it should have been phased out long time ago. Yes, we all are riding old stinking furnaces.
Let's focus a bit on the rise time. The shorter that time, the less the ignition will suffer from parasitic drain. Parasitic drain is caused by old and/or wet sparkplugs and/or detoriated plugcaps and/or old high tension cables. CDI systems clearly have the advantage here. Rise time with a CDI is extremely short, but the concept also has disadvantages: no burn time to mention one .

So the initial voltagespike opens up for voltages normally to low to overcome the air-resistance in the spark gap? I checked with a calculator and a 0.3"/0.70mm seems to be around 2000 volts (not sure if this applies tp wet/dry conditions but one could assume it would be lower in a gasolinemist)

Is all energy above the level of whats sufficient to ignite the fuel basically a waste of energy?

[HondaMan]

When we ohm out a coil, we are measuring straight line DC resistance. During operation, coil current is constantly starting and stopping many times a second. This brings inductive reactance into play. The higher the frequency (RPM), the greater the reactance. A 3 ohm coil could actual draw less current then a 5 ohm coil, depending on the inductance of the coils. Inductance is like inertia. There is more resistance to getting electricity moving than to keep it moving.

At the peak RPM of these engines (166.7 Hz) the lower reactance of these coils will not alter their impedance significantly. The effect you mention begins well up into the kHz range, like 30,000+... 

[Bailgang]

ill be in trouble with my daisy chained 0.4 ohm coils then?

Are they really 0.4 ohms? They won't even run with points, if they are. The points won't last but a few minutes, tops, if it runs at all. Normally the less-than-2.5 ohm coils are made for CDI or ECM-driven systems, where the spark is created 'backward' from ours, so to speak: the power is sent thru the coil at the moment of spark and they generate HV pulse then, discharging quietly afterward. The Kettering design on our bikes charges the coil up for a 'dwell' period, then stops suddenly to let the coil's magnetic field collapse and make the spark.

Yes they are however they're mini coils made by boyer bransden specifically for their electronic ign sys, I know because I've got the boyer bransden ign on my 77 F2. I doubt the coils would work on a points ign but I've never tried it either. And as Dave pointed out the coils are wired in series with each other, yeah that had me scratching my head too when i first wired it up but that's the way boyer bransden instructed and it works with no charging issues. I'm not promoting the boyer ign, just explaining it a bit.

[rotortiller]

coils are wired in series with each other, yeah that had me scratching my head too when i first wired it up

Must be 6 volt coils and is why they fire at the same time.

[HondaMan]

ill be in trouble with my daisy chained 0.4 ohm coils then?

Are they really 0.4 ohms? They won't even run with points, if they are. The points won't last but a few minutes, tops, if it runs at all. Normally the less-than-2.5 ohm coils are made for CDI or ECM-driven systems, where the spark is created 'backward' from ours, so to speak: the power is sent thru the coil at the moment of spark and they generate HV pulse then, discharging quietly afterward. The Kettering design on our bikes charges the coil up for a 'dwell' period, then stops suddenly to let the coil's magnetic field collapse and make the spark.

Yes they are however they're mini coils made by boyer bransden specifically for their electronic ign sys, I know because I've got the boyer bransden ign on my 77 F2. I doubt the coils would work on a points ign but I've never tried it either. And as Dave pointed out the coils are wired in series with each other, yeah that had me scratching my head too when i first wired it up but that's the way boyer bransden instructed and it works with no charging issues. I'm not promoting the boyer ign, just explaining it a bit.

I haven't seen Boyers in quite a while, but the last one I remember was a CDI unit, like is found on the later CB650 SOHC4 and the DOHC Fours. They are a pulse-discharge type, so the coils have very low impedance. Many modern cars (circa post-1990ish) are like this, too.

[rotortiller]

I haven't seen Boyers in quite a while, but the last one I remember was a CDI unit, like is found on the later CB650 SOHC4 and the DOHC Fours.

I thought the CB650 and DOHC 750s etc were transistorized and not CDI and they see 12 volts at the coils from the kill switch rather than say 300 volts from the CDI box. If I am mistaken I stand corrected.

[dave500]

the boyer which uses the stock honda coils also fires all four at once,those mini coils are also used on modern triumphs,boyer dont make them they are gill brand coils and another make which slips my mind right now.

[Bailgang]

coils are wired in series with each other, yeah that had me scratching my head too when i first wired it up

Must be 6 volt coils and is why they fire at the same time.

Well here's what confounds me. although the coils are clearly wired in series which you would think would mean it has a double wasted spark now, but it if it does it doesn't show it with a timing light. What I mean is that if all cyls are firing at the same time due to the coils wired in series then you would think that regardless of what plug wire I had my timing light on I should see both the 1-4 timing mark in one flash of the strobe and I should see the 2-3 timing mark as well in another flash of the strobe wouldn't you think? Nope, if my timing light is on say the #1 or #4 plug wire then the only timing mark my strobe will see is the 1-4 mark. I wont see the 2-3 mark unless I have the timing light on the #2 or #3 plug wire and again in that case my strobe will only see the 2-3 timing mark which makes it seem as though the coils are firing independently even though they're wired in series. My knowledge of electronics is limited but there seems to be some kind of electronic voodoo going on or I'm missing something.

[rotortiller]

Yea Scott, that sounds kind of funky. Are they indeed all firing at the same time is the question?

[HondaMan]

That's a pretty standard-looking spark trace. I'm adding the one from my Transistor Ignition for reference.
The tall trace is the first portion of the spark discharge, which bridges the gap and ionizes the air in between the tip and the ground arm. The next little "wiggles" that you see are still some spark back-and-forth between the electrodes (as described in too much detail in my book), but it is dying off slowly (so to speak) as the coil magnetically collapses and discharges. The square-turn back to 0 volts is where the points close again and the coil starts charging. During the 'flatline' portion that follows the wiggles (to the right of the wiggles) there is no more spark: that is just the residual voltage in the coil, which gets pulled back out when the points close. In very low-compression engines (or out in the air, no compression) the spark can sometimes linger that long, so often the made-for-sales videos we get to see (especially on the internet) purport this to be "longer burn time" for your engine - it is not, if your compression ratio is more than about 6:1 (80 PSI or more), because the pressure prevents the electrons from leaving the plug tip (they are effectively trapped there).

Regarding my image (on the green screen): the large spike is that ionization discharge that begins the spark, and the time that the spark stays "on" is the portion where there is an angled decline toward the final 'ringing' before the flat-line starts. When the flat-line starts, there is no more spark actually happening. This was taken on a running engine with good compression, showing a strong spark time of about 2.4 mS duration, using a TEC (Honda OEM) coil, generating about 7800v peak spark - each horizontal gridline is 200 volts high.

[Ben D]

Super cool concepts you guys are discussing here, never would have thought of spark duration having such importance..

[Deltarider]

Super cool concepts you guys are discussing here, never would have thought of spark duration having such importance..

Burn time is of more importance with lean(er) mixtures.

[DesertKyorugi]

Very good read here but still doesn't help me decide if I should spend $85 on oem style coils, caps and wires or $105 Magna coils, caps and wires 

What do you guys think? My JDM K1 has weak sparks from jacked-up Accel plug wires and caps