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Dyna coils 8 months 4 days ago #31558

  • PaulD
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I’ve ordered a set of Dyna coils for my bike. Do I need to remove the ballast resistor before I can use them? I’m an electrical idiot and don’t want to damage anything. 

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Dyna coils 8 months 3 days ago #31561

  • Kawboy
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20 views and no answers in 24 hours so I'll jump in here.

The primary resistance of the ignition circuit is critical  if you don't want to be replacing the igniter. The amperage flowing through the Darlington transistors has an upper limit and the way to control that is to maintain a primary resistance to restrict the flow of amperage.

In the Service Manual pages 240 and 241 it tells you how to measure the resistance in the ignition coils and the ballast resistor.
The resistance in the ignition coils should be between 1.2 and 1.9 Ohms
The resistance in the ballast resistor should be between 1.5 and 1.9 Ohms
Since the resistance in this circuit is in series, the total resistance of the circuit is the addition of all the resistance. that being said the total resistance of the primary ignition circuit is between  1.2+ 1.5 =2.7  to  1.9 + 1,9 = 3.8 Ohms
So, you can't have a primary resistance below 2.7 Ohms because the lower the resistance the higher the current and the higher current will fry the Darlington transistors which are the switches that turn on/off the power to the primary windings of the ignition coils.
Any resistance in the primary circuit higher than 3.8 Ohms and you're choking off the power to the ignition coils and will end up with a weak spark.


So. bottom line-
If you bought the Dyna coils with a primary resistance of 3.0 Ohms, no ballast resistor required.
If you bought Dyna coils with 1.0 Ohm resistance then you'll need to incorporate the ballast resistor
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Dyna coils 8 months 3 days ago #31562

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Sorry Kawboy. Hoping to save you from having to answer,   I wrote a response to this ( the subject having been covered many times before) whilst on the train this morning . Infuriatingly, when I clicked on ‘Submit’ I was greeted with the log-in page!  This site signs users out without warning, then all that I’d written was lost!  By that time , the train was at the station, and I haven’t had time to try again.  

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Dyna coils 8 months 3 days ago #31563

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Sorry Kawboy. Hoping to save you from having to answer,   I wrote a response to this ( the subject having been covered many times before) whilst on the train this morning . Infuriatingly, when I clicked on ‘Submit’ I was greeted with the log-in page!  This site signs users out without warning, then all that I’d written was lost!  By that time , the train was at the station, and I haven’t had time to try again.  
Regarding getting logged out and losing your post- It's happened to me several times and I've found that if you arrow back 2 or 3 pages, you're pre-submitted post is there, and when you try to submit it again, you'll find that you have been automatically logged back in and the post will submit and be accepted to the topic. Sounds weird and I can't explain it, but it has worked for me most of the time.
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Dyna coils 7 months 3 weeks ago #31576

  • Tyler
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I run the green Dyna coils with no resistor. They have very nearly the perfect  resistance to do so. This is on my 1981 wich has a very sensitive ignition computer. The earlier bikes with the CDI box might behave differently, but I belive a number of folks have run the green dynatek coils successfully without the resistor. It's best to remove it if you can as that resistor can chage its value as it ages and can cause problems. It is a known failure mode for the ignition controller on the 81 models.

Kawboy's math is correct, however resistance that is too high can raise the output voltage on those trasistors too high amd damage them as well. Wiring should be in good condition and good connections everywhere. 
1981 KZ1300
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Dyna coils 7 months 3 weeks ago #31577

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That's  a REALLY good point that  I missed and I shouldn't  have. It brings back memories of my Chrysler days. Ballast resistors in the Chrysler Dodge and Plymouths were mounted on the firewall and if you grabbed them just after shutting down a car, you would burn your hands on the ceramic insulator. The heat generated was intense and of course the load on the circuit included the resistor which is in fact something similar to an electric element.
I guess I should have burnt my hands a few more times to reinforce that point. Thanks Tyler for bringing this up. 

This one good reason for my desire to  Microsquirt my KZ1300 when the time comes. Because it's a Electronic Engine Management System, you can use any coil and by programming in the dwell, you can charge the coil to produce maximum power and control the primary input voltage/current dwell so that you don't power the coil more than required. So with Microsquirt  you could use a coil with a primary resistance of .6 ohms and run a dwell of 3 milliseconds. The advantage is that the coil charges rapidly which is a real advantage at higher rpm's since the on/off time ratio is still reasonable. Look at all of the 600cc superbikes running up to 16K rpms. That couldn't happen with high resistance coils because the saturation time required would be overlapping making it impossible to generate a spark.
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