return to points

Rev wrote: My dyna s ignition died for the second time, so I am reverting back to points (at least for now). My question is can I still use my Dyna 3ohm coils and cables with the points?

FYI, a flaky coil is one of the primary causes of blowing out an EI module. And the worst part is, it is impossible to detect the failure mode on the test bench when it only occurs "hot" with high voltage firing the plugs. Old coils start "arcing" back from the HV winding to the primary which lights up everything on the drive side of the coil.

Yes, but don't forget duty cycle.

Even with a 1 or 2 volt increase, the 50% duty cycle change results in a much lower average wattage dissipation, so converting to points will reduce the heat in the coil.

loudhvx wrote: the 50% duty cycle change results in a much lower average wattage dissipation, so converting to points will reduce the heat in the coil.

Unless you have the key on while you use a meter to check the bad wire to the turn signal or brake light or whatever... or (as has happened many times to me) you have your bike idling cold to warm up while you go back in the house to get your coat and gloves and the engine sputs and dies.

and a couple of minutes later, your coil is a useless burned up piece of junk because the points were closed and the key was on.

There is a reason you NEVER install a reduced impedance coil in a points system. It also affords ZERO increase in performance over a properly working stock coil system.

I would like to know if the original poster :lol: checked his voltage.

bountyhunter wrote:

loudhvx wrote: the 50% duty cycle change results in a much lower average wattage dissipation, so converting to points will reduce the heat in the coil.

Unless you have the key on while you use a meter to check the bad wire to the turn signal or brake light or whatever... or (as has happened many times to me) you have your bike idling cold to warm up while you go back in the house to get your coat and gloves and the engine sputs and dies.

and a couple of minutes later, your coil is a useless burned up piece of junk because the points were closed and the key was on.

There is a reason you NEVER install a reduced impedance coil in a points system. It also affords ZERO increase in performance over a properly working stock coil system.

Yes, but the point is, using a 3 ohm coil with points will not do any more harm to the coil than using the same coil with a Dyna S, in fact, the coil will actually run cooler with points.

In this case, which is what the original poster was asking about, the reason you may not want to use the 3-ohm coil is because the points will run hotter and thus the point life will shorten.

The Dyna S (that I tested years ago) does not do any current limiting or any voltage limiting (other than the normal 1 volt or so drop due the output transistor's e-c drop). It has a duty cycle about as close to 100% as you can get and still have time for the spark to discharge. Points are closer to a 50% duty cycle, thus the heat dissipation in the coil will actually be lower.

It's been a long time since I did any Dyna S tests, though, so in case a design change has taken place, it may be time to test a new one.

loudhvx wrote:

bountyhunter wrote:

loudhvx wrote: the 50% duty cycle change results in a much lower average wattage dissipation, so converting to points will reduce the heat in the coil.

Unless you have the key on while you use a meter to check the bad wire to the turn signal or brake light or whatever... or (as has happened many times to me) you have your bike idling cold to warm up while you go back in the house to get your coat and gloves and the engine sputs and dies.

and a couple of minutes later, your coil is a useless burned up piece of junk because the points were closed and the key was on.

There is a reason you NEVER install a reduced impedance coil in a points system. It also affords ZERO increase in performance over a properly working stock coil system.

Yes, but the point is, using a 3 ohm coil with points will not do any more harm to the coil than using the same coil with a Dyna S, in fact, the coil will actually run cooler with points.

I doubt it. The ignition has to have some kind of transistor in series with the coil winding which eats up significant voltage drop. The coil winding sees significantly less than full 12V. That's why they use lower impedance coils.

loudhvx wrote:

bountyhunter wrote:

loudhvx wrote: the 50% duty cycle change results in a much lower average wattage dissipation, so converting to points will reduce the heat in the coil.

Unless you have the key on while you use a meter to check the bad wire to the turn signal or brake light or whatever... or (as has happened many times to me) you have your bike idling cold to warm up while you go back in the house to get your coat and gloves and the engine sputs and dies.

and a couple of minutes later, your coil is a useless burned up piece of junk because the points were closed and the key was on.

There is a reason you NEVER install a reduced impedance coil in a points system. It also affords ZERO increase in performance over a properly working stock coil system.

In this case, which is what the original poster was asking about, the reason you may not want to use the 3-ohm coil is because the points will run hotter and thus the point life will shorten.

Current is not what wears out points, it's the voltage arcing which occurs when they open. I doubt it has a significant effect on point life, maybe slight.

loudhvx wrote:

bountyhunter wrote:

loudhvx wrote: the 50% duty cycle change results in a much lower average wattage dissipation, so converting to points will reduce the heat in the coil.

Unless you have the key on while you use a meter to check the bad wire to the turn signal or brake light or whatever... or (as has happened many times to me) you have your bike idling cold to warm up while you go back in the house to get your coat and gloves and the engine sputs and dies.

and a couple of minutes later, your coil is a useless burned up piece of junk because the points were closed and the key was on.

There is a reason you NEVER install a reduced impedance coil in a points system. It also affords ZERO increase in performance over a properly working stock coil system.

The Dyna S (that I tested years ago) does not do any current limiting or any voltage limiting (other than the normal 1 volt or so drop due the output transistor's e-c drop). It has a duty cycle about as close to 100% as you can get and still have time for the spark to discharge. Points are closer to a 50% duty cycle, thus the heat dissipation in the coil will actually be lower.

It's been a long time since I did any Dyna S tests, though, so in case a design change has taken place, it may be time to test a new one.

As I said, even if the Dyna coil will handle points, there is no upside to running a lower impedance coil, especially when the four Ohm OEM coils are available for $36 with new wires. Running a 3 Ohm coil just adds power load to the wiring and doesn't increase performance. I think it also kills the coil faster.

Id be checking my grounds, Ive had the same Dyna setup with green coils on my 78 for 34 years

bountyhunter wrote:

loudhvx wrote:

bountyhunter wrote:

loudhvx wrote: the 50% duty cycle change results in a much lower average wattage dissipation, so converting to points will reduce the heat in the coil.

Unless you have the key on while you use a meter to check the bad wire to the turn signal or brake light or whatever... or (as has happened many times to me) you have your bike idling cold to warm up while you go back in the house to get your coat and gloves and the engine sputs and dies.

and a couple of minutes later, your coil is a useless burned up piece of junk because the points were closed and the key was on.

There is a reason you NEVER install a reduced impedance coil in a points system. It also affords ZERO increase in performance over a properly working stock coil system.

Yes, but the point is, using a 3 ohm coil with points will not do any more harm to the coil than using the same coil with a Dyna S, in fact, the coil will actually run cooler with points.

I doubt it. The ignition has to have some kind of transistor in series with the coil winding which eats up significant voltage drop. The coil winding sees significantly less than full 12V. That's why they use lower impedance coils.

You can doubt it, but I measured it. It's about 1.1v using a 3 ohm coil with a 14v supply.
Yes the holy grail of transistors would be to have zero collector-emitter drop at full saturation. Transistors are not that good, but they are certainly not as bad as you are saying. Typical Darlington C-E drop is around 1v to 1.5v on most ignitions I've tested, including the one I designed from scratch. That's for ignitions where the coil current is in the range we typically see... 3 to 6 amps or so.

The reason for using faster coils is not because of the small voltage loss in the transistor, it is because you can make an ignition much more efficient by using a small dwell and matching the coil to it. By smartly varying dwell, and using a fast coil, you can get a very good spark while using less than an average of 1 amp. But it takes a little more design work to do it. This cannot be done with points because the high instantaneous current, at the moment of spark, will greatly degrade points when used with a low impedance coil. (By low, I mean less than about 1.5 ohms. Slightly lower (3 ohms) will only slightly reduce point life.)

The Dyna S is designed to be inexpensive, and since it is designed to use the original points coils, it must have a relatively large dwell. This is all to make the ignition available to the end user with the lowest possible cost.

bountyhunter wrote:

loudhvx wrote:

bountyhunter wrote:

loudhvx wrote: the 50% duty cycle change results in a much lower average wattage dissipation, so converting to points will reduce the heat in the coil.

Unless you have the key on while you use a meter to check the bad wire to the turn signal or brake light or whatever... or (as has happened many times to me) you have your bike idling cold to warm up while you go back in the house to get your coat and gloves and the engine sputs and dies.

and a couple of minutes later, your coil is a useless burned up piece of junk because the points were closed and the key was on.

There is a reason you NEVER install a reduced impedance coil in a points system. It also affords ZERO increase in performance over a properly working stock coil system.

In this case, which is what the original poster was asking about, the reason you may not want to use the 3-ohm coil is because the points will run hotter and thus the point life will shorten.

Current is not what wears out points, it's the voltage arcing which occurs when they open. I doubt it has a significant effect on point life, maybe slight.

Voltage causes the arc at the points, but it quickly drops down to double-digit voltages once it is struck. It is the current that does the damage. By that I mean the instantaneous current when the arc is struck. The more current you have, the more energy is dissipated in the plasma. Also with more current, you get deeper penetration into the metal, and you get more metal transfer. That's what shortens the life of points. Anyone who arc welds, knows that increasing the current gets you more heat, and more penetration in a weld. The arc at the points is essentially doing the same thing. This is why one side of the points will have a pit, but the other side will actually have a bump.

There is a secondary effect to having higher current in the points. When the average current through the points increases, the average temperature of the points increases. This also aggravates the damage to the points since the metal will be that much easier to melt.

Incidently, when the points are closed, the voltage drop on the points is not zero. With a scope, you can see the voltage drop on the closed points increase as the points heat up. So the negative effects of the voltage drop seen on a transistor is mitigated.

bountyhunter wrote:

loudhvx wrote:

bountyhunter wrote:

loudhvx wrote: the 50% duty cycle change results in a much lower average wattage dissipation, so converting to points will reduce the heat in the coil.

Unless you have the key on while you use a meter to check the bad wire to the turn signal or brake light or whatever... or (as has happened many times to me) you have your bike idling cold to warm up while you go back in the house to get your coat and gloves and the engine sputs and dies.

and a couple of minutes later, your coil is a useless burned up piece of junk because the points were closed and the key was on.

There is a reason you NEVER install a reduced impedance coil in a points system. It also affords ZERO increase in performance over a properly working stock coil system.

The Dyna S (that I tested years ago) does not do any current limiting or any voltage limiting (other than the normal 1 volt or so drop due the output transistor's e-c drop). It has a duty cycle about as close to 100% as you can get and still have time for the spark to discharge. Points are closer to a 50% duty cycle, thus the heat dissipation in the coil will actually be lower.

It's been a long time since I did any Dyna S tests, though, so in case a design change has taken place, it may be time to test a new one.

As I said, even if the Dyna coil will handle points, there is no upside to running a lower impedance coil, especially when the four Ohm OEM coils are available for $36 with new wires. Running a 3 Ohm coil just adds power load to the wiring and doesn't increase performance. I think it also kills the coil faster.

Well I don't dispute that there are few, if not zero, reasons for a points ignition to use a lower impedance coil. But the original poster wanted to know if the coil would be damaged by using points. If he is only worried about the coil, and can live with a slight reduction in point life, then he can save $36. That's the upside.

OK, well I would not use a 3 Ohm coil designed for elect ignition with points unless the coil maker says it is OK. Actually, I would never do it at all since it stresses the bike's electrics with no gain or benefit.

As for the arcing at the points: the voltage arc across the point is a direct consequence of the equation:

V = L dI/dt

Which is to say, the voltage across the points is proportional to the RATE of current change in the coil's primary when the points open, not the total magnitude of the current when they are closed. It's also dependent on the coil's inductance. Ergo, a lower inductance coil carrying more current may actually give less arc voltage. If the coil is eating points, it probably has higher inductance than stock.

bountyhunter wrote: ...As for the arcing at the points: the voltage arc across the point is a direct consequence of the equation:

V = L dI/dt

Which is to say, the voltage across the points is proportional to the RATE of current change in the coil's primary when the points open, not the total magnitude of the current when they are closed. It's also dependent on the coil's inductance. Ergo, a lower inductance coil carrying more current may actually give less arc voltage. If the coil is eating points, it probably has higher inductance than stock.

v = L di/dt describes the voltage on the inductor portion of the coil (don't forget the coil also has resistance). If you ignore the condenser and the capacitance of the coil and the capacitance of the wiring and plugs, then it may give you an approximation of the voltage on the points before any arc. But we don't really care what the voltage is before there is an arc.

Once there is an arc, the problem escalates to a RLC-discharge problem, in which case we cannot ignore the resistance and capacitance. We can use superposition to put the coil's inductance in series with the coil's resistance. But v = L di/dt still only describes the voltage on the inductor portion of the coil, which is not what is on the points or on the arc or even on the resistance of the coil. The voltage generated by L di/dt is reduced at the points by the voltage drop of resistance of the coil. And it is further complicated by the fact that the coil is a transformer coupled to the arc at the spark plugs.

The magnitude of the current at the time of the arc is what the inductive reactance of the coil is trying to maintain. And, as is seen in arc welding, more current creates more metal heating and penetration.

A simple experiment shows the difference. I put 13v on two coils. One was a 2.2 ohm Dyna coil for use with electronic ignitions, and the other was a 4 ohm stock coil from a KZ650.

I just did some simple stippling using a plate of zinc-plated steel and a zinc-coated wire connector to simulate points.
I also did some scratch tests.

The photos show the results.
The area marked "4" was the KZ650 points coil.
The area marked "2" was the Dyna Electronic ignition coil.

I did several trials and these are ones with the greatest effect I could get with the 4 ohm coil.

First the stippling test:



Spots of the 2.2 ohm coil were clearly bigger.


Next the scratch test:



Also, the sparks produced were noticeably more impressive on the 2.2 ohm coil.

seen so much trouble with dyna S that no surprises here.... they just fail. its common knowledge at least where i race.

black boxes + pickups from many 80-90 fours can be easily adapted and are bullet proof.

never had to touch again the gsxr ignitions in my racers after mounting them

kzrider.com/forum/2-engine/410994-gpz750...g?limit=20&start=100

But the original poster wanted to know if the coil would be damaged by using points. If he is only worried about the coil, and can live with a slight reduction in point life, then he can save $36. That's the upside.

I don't agree. I come from an electronics industry and I don't think it's safe to overstress a coil unless the manufacturer specifically says it is "overdesigned" enough to allow it. And even then I would not do it because I know what a "coil" is, it's actually a high voltage flyback transformer... and I have designed a few of those. They are notoriously prone to failure from HV stress on the winding's insulation which is exponentially increased by escalating heat stress (those of us who used to service color TV's know the flyback transformers fail more than all the other problems together). It's also the reason so many older bikes have coil problems: they are super heated to begin with and they don't age well. So basically, for a question of:

Is it OK if I throw about 30% more power dissipation into my coil with no increase in performance or benefit?

I am going to say NO every time.