Testing Coils

No disrespect intended Scorpio, but I've stayed out of this discussion because trying to explain all this deeper electronics part of ignition is quite hard to guys who know something about basic electronics, and it's just plain voodoo to anybody who doesn't have a firm grip on the basics.
But, for the benefit of those who can follow, I brushed up on the stats of a ZN's coils. Are we talking ZN coils, or KZ coils? As you can tell by the fact that they don't refer us to the basic manual, the two systems are not the same. So, I will be talking strictly about the ZN coils here. I know nothing about the KZ system,.......YET!
You guys keep talking about these "hotter" aftermarket coils with 3ohm primaries. Strike three! You're already out! ZN coils have a rated service limit of 2.8ohms. 3 ohms will most likely work,.....for a while, but without more detailed info on the engineering of this system from Kawasaki, we don't really know what the ignitor's limits are in tolerance. There's got to be a good reason why they spec'd 2.8ohms, and you guys are STARTING OUT outside the limits allowed.
First of all, that higher resistance will undoubtedly cause a lower amperage, which in turn lowers the amount of POWER (watts) being put into the coil. You can't get out more power if you put less in! So, your output (spark) suffers from either the voltage available or the current. The voltage will determine how reliably the spark will jump the gap and how much "crud" (air/fuel/pressure and all other atmospheric crap induced!) that it can penetrate when trying to fire. And, of course, the first job is to jump that gap! VOLTAGE does this!
Next, to completely burn things you need a certain amount of heat in the spark, and this comes from the available current (amps). Higher current gives higher heat in the spark.
OK, hang on! It gets deep here!
As I said, with a 3ohm primary coil you have already reduced the power being fed INTO the coil, so the output will also be less. What is power (watts)? It's amps times volts. If one goes up, the other goes down to maintain the overall power available. So, now we have lower spark "power" available. These hotter coils are adding windings to bump the voltage, but the spark is cooler. They want that spark to jump a bigger gap to impress the buyer, but there's absolutely no way to measure the amperage to know how hot that spark is. That will only come when you test the bike with those coils. And, I can almost guarantee that those 3ohm coils won't work as well as a healthy stock coil!
As Kawboy said, there is a LOT of engineering that goes into balancing everything in an ignition system to get the best spark for the engine's needs. I could talk for a week about all the parameters that are involved, and still not cover it all. Even the engine's RPM's affect the design. Higher RPM's require tuned circuits to prevent inductance and reluctance.
So, for those who don't know the basics, how can it be explained well enough to send you out there to make an educated decision?
Again, I will go out on a limb here and say that there are some areas that some people just shouldn't be messing with. Modifying these ignition systems is one such area to leave absolutely stock. If you can't afford to do this, then you can't afford this hobby! It would be like finding out that you have a brain tumor, so you go to a forum to learn how to replace yours with an aftermarket unit from who-knows-what! Just pay the doctor's price and let him fix you!
Even as wordy as I may have been here, this isn't even the tip of the iceburg. I have only tried to address one of the issues of using these "hotter" 3ohm miracle coils.
Kawboy, after reviewing the supplement, you correctly concluded that the primary and secondary are indeed two separate windings, and they even have you test for ANY connectivity between them. There should be none!
Also, nobody has addressed the issue of dielectric and insulation deterioration of these older coils. Electronics is a "game" of things you cannot see! All plastics deteriorate over time, and part of this decay is the insulative properties, so even though it may not have directly shorted to ground, the coil's case can be leaking slightly. Wanna test this? Hold the coil in one hand while holding something grounded on the bike with your other hand with the engine running. Now rev it hard! With a new coil you could do this, but with a 35 year old coil,.....well,.....I hope you didn't want any more normal kids! And, the decay will also allow some of the secondary voltage to bleed into the primary windings, blowing the output circuit of the ignitor.
I hope it's beginning to sink in how complex and inter-dependent all this ignition stuff is, and why you can't just slap some hot coil in place and go riding.
Unfortunately, there are probably no more new (NOS) factory coils left out there to use strictly for testing.
Want me to complicate it even more? Let's talk briefly about tuned circuits. These aftermarket coils can have both primary and secondary windings made from larger gauge wire, but more turns to give the same resistance readings as a stock coil. Or, fewer turns of smaller wire! Remember me using the words "inductance" and "reluctance". Well, these changes in number of turns of wire and size of wire will also change the inductance and reluctance values of the coil, and the system was designed for particular values to handle the effects of harmonic frequencies that begin to be generated and become important at higher RPM's! This new imbalance from an aftermarket coil can actually cause a misplaced spark to occur, causing the cylinder to fire at the wrong time, robbing you of power or burning a valve or piston top.

OK, back your issue, Scorpio. If those pretty new 3ohm coils are working for you, cross your fingers that the higher primary resistance doesn't cause cold weather hard starts. Did you take a resistance reading between their secondaries (plug wires)? Stock coils call for 10.4kohms to 15.6kohms. I would be willing to bet they fall near, or above the higher resistance. 15kohms-20kohms. Great for jumping the gap, but won't give complete combustion! Pipes will get black and you may foul plugs.
Isn't ignition fun?
:lol: :lol: :lol: :lol: :lol: :lol:

OK, just a brief(?) followup.

I did review the KZ's manual and the KZ does use a resistor feeding the +12 volts to all three coils, then the ignitor grounds each coil to fire it. The ZN does NOT use this resistor.

However, both systems do use a coil with totally separate primaries and secondaries.

So in your obviously educated opinion should working stock coils (which I have) not be replaced with Honda AW82 coils unless the originals fail, and the same with the expensive aftermarket "upgrade" coil packs?

The standard Z1300 coils fitted to most carb models (with ballast resistor) are very poor quanity and low output.
This can and often does make starting and general running problematic and poor.

The AW82 coil with no Ballast Resistor fitted produces a much better quality spark without doing any potential damage to your CDI unit.
If your ballast resitor ever fails, it will normally result in your coils frying your CDI unit.

In summary, the bike will run at a better, more efficient level with the AW82 coils fitted............fact.

This is the main reason why you will never find any new bike now with a coil ballast resitor fitted, as its very old outdated technology.

Pete F
UK

charlie9670 wrote: So in your obviously educated opinion should working stock coils (which I have) not be replaced with Honda AW82 coils unless the originals fail, and the same with the expensive aftermarket "upgrade" coil packs?

I don't know anything about the Honda coils, nor the upgrade coils. Never had them in my hands to test them for specs, so I can't honestly say anything about them.
BUT, I will say that without any comparative data on them, it's like Russian Roulette using them to replace stock coils.
I would also like to add to all of this discussion that simply testing for DC resistance isn't the whole story! An ignition coil is a coil of wire, just like a "choke", or a coil in a radio tuned circuit, AND, the rest of the ignition circuit does constitute it's own overall resistance and capacitance. Therefore, between the coil and the ignitor circuits, you have a tuned circuit that I spoke of earlier. That tuned circuit has to be maintained to factory specs or various RPM ranges (frequencies) can create excessive, or even attenuated, currents in the primaries as well as the ignitor outputs. At even 1000RPM (idle) the ignitor is creating 3000 firing pulses/min!!! Another way to look at it is that each of the three separate outputs of the ignitor has to fire two spark plugs, and since each cylinder is paired with another one that fires 360 crank-degrees apart, each output fires every revolution of the crank. So, at 1000RPM each ignitor output is firing 1000 times/min. This is approaching lower radio frequencies, and we're still basically at idle! It gets more critical as the RPM's increase.
I hope I've made my point about how important it is to maintain the stock design parameters for overall performance and longevity. To really test the viability of any given coil, other than stock, it would require watching the primary circuit of that coil on an oscilloscope to see how the voltages and currents at various RPM's compare to the stock coil.
Remember when I said that you can get the same resistance value from a "hotter" coil by increasing the number of turns of larger wire, or decreasing the number of turns of smaller wire? Well, that resistance would be measured with a DC ohmmeter and not an AC reluctance meter at a particular frequency. Also, when you alter the number of turns of wire in a coil, you alter it's reluctance (AC), if not it's resistance (DC). This de-tunes the output circuits and can cause those unwanted increases/decreases in output current, either burning the outputs or losing spark intensity.

I will try to say this one more time. UNLESS you can get all of the engineering specs for the factory system as well as the specs for any aftermarket coils, then make an educated analysis of all of that data, you are simply shooting in the dark using anything but stock parts in the ignition system!

I will also ask this again, more to make you think about this for yourself. WHY do you think you need a "hotter" spark for your bike than what the Kawasaki engineers have provided? If you do NEED a hotter spark to improve your engine's performance, you are simply trying to mask another issue causing this need! The ONLY exceptions to this would be an engine heavily modified with higher compression, different fuel used (alcohol, nitro, NOS), or mechanically augmented breathing (turbo, supercharger). A simple change to free-flowing headers will not require a hotter spark. Also, trying to improve things by a single change will invariably DECREASE overall performance one way or another unless you are a retired Kawasaki electrical engineer and make appropriate alterations to the whole system!

BTW, "FACT!", these bikes do not have a CDI unit! "CDI" stands for Capacitive Discharge Induction, and refers to a completely different way of creating the spark. Let's get the terminology straight!
These sixes, in both the KZ and ZN, use a simple pickup coil amplification circuit to turn on and off the outputs of Darlington power transistors to control the current to the coil primaries. This is all explained in the main "Theory " section of the KZ's manual. Not the most exciting reading, but how can we have an intelligent discussion if we don't use correct terms and get on the same page?