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Re: sourcing new starter
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Quote:
They are a transformer with two windings. However, in most ign coils the windings are tied together at one of the terminals so essentially it becomes a single coil of wire with a connection at one end and another somewhere farther up and then the third for the plug wire. Quote: If you change the wires so the polarity is correct as shown, you get the full effect of the entire winding between ground and the HV terminal. If you don't, then essentially the bottom or primary part is out of the circuit as far as the secondary is concerned since ground is now several hundred turns of the way up. The reverse in polarity also makes the spark want to jump from the shell to the center electrode which also reduces efficiency. This is, with out a doubt, the best explanation yet altho I think it is a bit incorrect. The only thing that would change,as I see it,is the direction of the spark across the spark plug. Quote: The spark is more efficient when jumping from the center electrode to ground rather than other way around. Here is a brief description of how to check.http://www.fifthaveinternetgarage.com ... ips_ign_coil_polarit.html
Posted on: 2010/5/12 14:14
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Re: sourcing new starter
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The only thing that would change,as I see it,is the direction of the spark across the spark plug. Am not quite following unless my poor choice of words confused the issue. You always want the spark to jump from the plug wire or center electrode to the shell which would be the case with proper polarity is what I was trying to say. Another old test was to take a pencil (If you do, use one with heavy wood and maybe even a glove on) and place it between the wire and plug or wire and ground. Here is an illustration from a site showing the correct polarity. Attach file:  (12.78 KB)
Posted on: 2010/5/12 14:49
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Re: sourcing new starter
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HH56 - Thank you for your time and efforts in suffering this explanation. Since both windings are tied together the connection of the coil to the battery source and distributor is important. I did not understand that both windings were connected. We all, especially me, owe you a great deal of thanks. I am glad I learned something new today.
(o{I}o)
Posted on: 2010/5/12 16:11
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Re: sourcing new starter
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Quote:
Am not quite following unless my poor choice of words confused the issue. You always want the spark to jump from the plug wire or center electrode to the shell which would be the case with proper polarity is what I was trying to say What I was trying to rebut was the statement that the length of the secondary winding would change if the battery polarity were reversed. That the shorter primary winding would not be included if the polarity were reversed. That is not the case. The field built up by the primary winding and allowed to collapse will act on the two windings exactly the same producing the same voltage. The only thing that would change would be the direction of the induced voltage causing the spark to jump from the outer part of the plug to the center electrode instead of the other way around. Frankly I tend to believe that the plug may spark better in one direction however I don't know why that would be. It is not due to a lower voltage because reversing the battery polarity does not change that. Voltage stays the same. Added: An ignition coil, if my memory serves me, is called an auto transformer. The primary is the shorter of the two windings however it becomes part of the secondary wile the built up field is collapsing. Again battery polarity does not change that.
Posted on: 2010/5/12 23:12
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Re: sourcing new starter
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One of the web sites mentioned explains the reason why the plug is more efficient when spark comes from center electrode. It runs hotter than shell and since electrons flow more easily from a heated surface, it takes less effort for the spark to start.
Ign coil is an autotransformer and you have a point in that the number of coils won't change so the induced voltage wouldn't either. My thinking was with the ground being at the bottom with the primary coils included in circuit, there would be x number of total windings but if the connections were reversed, and ground was effectively at the end of secondary winding then it would be secondary windings primarily developing the overall number with minimal input from the primary so voltage would be slightly lower. Admittedly, my transformer theory is rusty and this application is different since you are relying on the magnetic core with the collapsing field rather than a constant excitation. Still, even though you do have the same number of windings with the primary becoming part of secondary, am just not understanding how much it will contribute since you are effectively referencing the voltage in question between a tap point and output. I don't see a clear path for the primary windings to be included unless there is feedback thru something else or ringing involved.
Posted on: 2010/5/13 8:54
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Re: sourcing new starter
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Electrical engineering and theory are above me, but if I may summarize: If the coil's terminals are marked with "+" and "-", and the electrical system is positive ground, then the positive marked terminal of the coil is connected to the distributor and the opposite connection for a negative ground system. Thanks again to HH56 and Bob1951 for their insightful contributions to this discussion.
(o{I}o)
Posted on: 2010/5/13 10:23
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Re: sourcing new starter
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Bernardi wrote: Quote:
It may not be original, but I converted my 55 400 to negative ground and installed an alternator. Need to reverse the ampmeter and change a coil wire, but everything else works. This "sparked" the above informative discussion about coil polarity. It is also important to note for those with the original 55 Positive ground who are contemplating switching to Negative ground (for whatever reason) that one does NOT have to replace the original generator. All that is required is to repolarize it (the proceedure is in the SM). You may also have to replace the regulator (on the core support) with one which will handle the reversed polarity, as the original one probably will not. You can still buy regulators which will work with either polarity and they look exactly the same as the OEM one. Craig
Posted on: 2010/5/13 12:49
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Re: sourcing new starter
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Quote:
am just not understanding how much it will contribute since you are effectively referencing the voltage in question between a tap point and output. Just draw out your own copy of the drawing from the above post and don't place the battery polarity symbols on the drawing just yet. Then place the + and - on the battery connections either way then reverse them. You will then see that the plug is still across the entire coil (primary and secondary) no matter how the battery is connected. Don't get hung up on the word ground. In this case "ground" really doesn't mean anything. The ckt will work the same no matter what the battery polarity is. I accept the explnation regarding why it is better for the spark to travel from the center electroide to the outer case of the plug.
Posted on: 2010/5/13 21:10
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Re: sourcing new starter
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Didn't realize how much discussion my comment would start. I've learned a bit from it, and thank those involved.
As Craig said, it is not necessary to go to an alternator when reversing the polarity of a 55. I did it(changed polarity) because Vintage Air said their units wouldn't work with positive ground systems. I installed an alternator to handle the increased load, particularly at low engine speeds.
Posted on: 2010/5/14 10:29
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