The Autonerdz Community Forums - Secondary voltage Question

James H Senior Member Picogroup Offline Bike Nerd Posts: 165 Waterloo Ontario Canada Gender:	Secondary voltage Question Apr 6^th, 2019 at 10:36am Here is a capture of a CDI Secondary ignition Voltage on 2 different coils using a spark plug tester set at a 15mm gap. If the conditions have not changed, how is it possible to have 2 very different firing voltages?
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Spence LSD Guide Picogroup Offline Posts: 8,025 Jeffersonville Pennsylvania USA Gender:	Re: Secondary voltage Question Reply #1 - Apr 6^th, 2019 at 11:09am Can you post your reference capture?
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James H Senior Member Picogroup Offline Bike Nerd Posts: 165 Waterloo Ontario Canada Gender:	Re: Secondary voltage Question Reply #2 - Apr 6^th, 2019 at 3:51pm Spence, here you are.
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James H Senior Member Picogroup Offline Bike Nerd Posts: 165 Waterloo Ontario Canada Gender:	Spark Gap to Voltage Chart Reply #3 - Apr 6^th, 2019 at 4:00pm You might find this interesting, I did.
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Spence LSD Guide Picogroup Offline Posts: 8,025 Jeffersonville Pennsylvania USA Gender:	Re: Secondary voltage Question Reply #4 - Apr 6^th, 2019 at 5:49pm James H wrote on Apr 6^th, 2019 at 4:00pm: You might find this interesting, I did. I do! Do you have a link to the article this came from?
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James H Senior Member Picogroup Offline Bike Nerd Posts: 165 Waterloo Ontario Canada Gender:	Re: Secondary voltage Question Reply #5 - Apr 7^th, 2019 at 6:55am https://hackaday.com/2016/12/08/measuring-high-voltage-in-millimeters-and-other- hv-probe-tricks/ I attached another interesting article as well.
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Spence LSD Guide Picogroup Offline Posts: 8,025 Jeffersonville Pennsylvania USA Gender:	Re: Secondary voltage Question Reply #6 - Apr 7^th, 2019 at 9:08am James H wrote on Apr 7^th, 2019 at 6:55am: https://hackaday.com/2016/12/08/measuring-high-voltage-in-millim eters-and-other-hv-probe-tricks/ I attached another interesting article as well. Thanks James!
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StitchB

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Re: Secondary voltage Question
Reply #7 - Apr 8^th, 2019 at 8:16am

James H wrote on Apr 7^th, 2019 at 6:55am:

https://hackaday.com/2016/12/08/measuring-high-voltage-in-millim
eters-and-other-hv-probe-tricks/

I attached another interesting article as well.

James will read up some. All I know is CDI is strange. Normal burn time on older regular coils like 1 to to MS, these are 1/4 of that. Then watch it going below ground some times, mostly not. The burn time looks like AC, noticed that on my KLR also and the coil is excited with AC not DC, again different.

I wonder if the CDI has individual capacitors for each jug, just talking out loud here, might explain the difference, don't know.

Larry

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James H

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Re: Secondary voltage Question
Reply #8 - Apr 8^th, 2019 at 1:18pm

Hi Larry, thanks for chiming in. It is actually a single cylinder XL600 Honda so very close to your KLR. I am just using a spark tester grounded on the cylinder set at a 15mm gap. I have just swapped coils. What bewilders me is the old coil will not jump more than the 15mm gap, the new one will but why when checking both at a 15mm gap is the voltage shown on the scope different higher for the new coil? If the spark voltage required is a function of the gap only (everything else being equal) should not the new coil put out the same even thou it has potential to put out more?
By the way, the new coil does put out higher voltage than the old coil when tested "in the engine " running as well.

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StitchB

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Re: Secondary voltage Question
Reply #9 - Apr 10^th, 2019 at 6:04am

James, has me befuddled. As stated much like a KLR, coil voltage is obviously AC, and alost 170 volts on the top side, my KLR more like 120.

What is interesting on normal coils in cars is the hight the KV, usually the shorter the burn time and vice versa meaning resistance down stream, plug, plug wire to plug, plug wire to coil.

On these with almost double on the one over the other there is no burn time change, somewhere around 270 microseconds, less than 1/4 of what we are used too in normal fire, and actually anything less the 1MS is broaching on a misfire.

One last thing, make sure grounding on the head is same same, 100% or your testing is going to be skewed, JMO.

Question, is the tester quality, same plug, blah, blah, blay, other than that can't answer it...

If like KLR CDI is excited right of the alternator in KLR about 120 volts, yours seems higher, but according to you files that number remained stable on both test and KR almost double from one to the other.

LARRY

Question, is the tester quality, same plug, blah, blah, blay, other than that can't answer it...

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