Dyna Coils

Discussion in 'Airheads' started by England-Kev, Jul 24, 2013.

  1. England-Kev

    England-Kev Long timer

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    My R80st runs a dual output 1,5 ohm dyna coil (brown) now I want to check if I have a coil problem, but all I have available is a 3 ohm (green) dyna coil, will I do any harm using this for an hour, while I test my bike on the road?
    #1
  2. Plaka

    Plaka Brevis illi vita est

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    Possibly. Too much draw through the ignition.

    if you want to know if you have a coil problem, just test the coil. It makes nice fat blue white sparks hot and cold or it doesn't.

    Put a clean plug on the end of one spark plug wire, lay the plug on the head and secure it with a bungie. (if it falls off you fry the ignition, immediately), crank the engine and look at the spark. Then put the plug wire back on your installed plug, go for a ride to heat things up (like the coil), and repeat the test. Don't use your best bungie, that head is hot. You can also hold the plug against the head with a silicone pot holder or similar.

    If the test reveals bad sparks, test the wires before you replace the coil.
    #2
  3. Steve W.

    Steve W. Boxer Pilot

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    More resistance (ohms) = Less current. (amps) At the same V (voltage) I=V/R.
    The 3 ohm coil will result in about 4.66 amps.
    The 1.5 ohm coil will result in about 9.33 amps.
    This is at 14v supply.
    I don't know if it will run, but the 3 ohm coil will
    draw less current.

    Cheers
    Steve
    #3
  4. supershaft

    supershaft because I can

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    You can test a coil bad but you can't test one good. The only way to do that is to try another coil. Some people say they run 3 ohm coils with no problem. The trouble is at high rpm they are going to make a weaker spark than a 1.5 ohm. Personally, I run a grey 1.2 ohm coil in that situation. You want as low as you can get without going too low. 1.5 is fine. 3?
    #4
  5. 190e

    190e Long timer

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    A 3 0hm coil will pull half of the current. The only time a coil pulls Ohms law current as an average is with ignition on and the engine not running. Once running the average current falls to under half and falls further with higher revs. Can't see a reason why it wouldn't work at least as well as a points ignition using the same coil. Only unknown is whether the ICU uses dwell control that would prevent the 3 ohm coil getting close to saturation but I'm not sure they are that sophisticated. Can't see how it would do any harm anyway.
    #5
  6. StephenB

    StephenB G(/)S ... what else!

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    It'll run just fine with a 3Ohm coil, you wouldn't know the difference.
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  7. supershaft

    supershaft because I can

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    I agree. At least for most people. If they do cut into higher rpm power for a weaker high rpm spark, most people never rev their beemers that high and hard anyway. Read the gas mileage thread. To a lot of people revving their beemer to 5k rpm is really giving them hell. :lol3 That makes 49mpg possible perhaps?
    #7
  8. mattcfish

    mattcfish R90X

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    Just to clear some things up. A brown Dyna is a 6 volt 1.5 ohm coil. A green is a 12v 3 ohm, a grey is a 6 volt 2.2 ohm. THE GREEN WILL WORK IF USED AS A SINGLE COIL FOR 2 SINGLE PLUGS (at least on early bikes originally equipped with points). Some Dyna ignitions will use two greens for dual spark, but most use the browns (dual spark only). My Sachse ignition likes the 2.2 ohm greys (dual plugged heads).
    #8
  9. England-Kev

    England-Kev Long timer

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    6v ? I would be interested to know how you work that out?:huh
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  10. ericrat

    ericrat Long timer

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    I think this is mistaken advice. I suggest doing further research. See the instruction here: http://www.powercommander.com/downloads/Support-Released/Dynatek/Manuals/StandardCoil.pdf

    A single, dual output 1.5 ohm coil is too much amperage draw (1.5ohmsx12volts= ~6 amps) for points.

    Eric
    #10
  11. bone13

    bone13 Been here awhile

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    Not sure myself on dynatechs specs per coil, but on the dual coil airheads the coils are 6v as they are run in series.

    Years ago I used Bosche 6v Blue coils from 60s 6v VW beetles as a coil replacement/ performance mod. BMW coil was $150+ bosche blue coil was $39
    But that was way back in the day... lol
    #11
  12. supershaft

    supershaft because I can

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    I talked on the phone with someone at Dyna and he told me that there was no difference whatsoever between their 6 and 12 volt coils and that they sold them as such just to make things easier on themselves.
    #12
  13. ericrat

    ericrat Long timer

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    That matches my experience and measurements. I have tried to measure a difference between Dyna 6 and 12 volt coils and couldn't find one. I think it is possible that there are coil winding turn ratio differences and some other subtle things inside. Dyna probably wouldn't divulge that kind of proprietary build data anyway.

    None of that would make any difference however, expect racing at high RPM. One of these days I when I go racing again and I sort out all the other performance stuff I will come back to serious ignition optimization. I have an idea that a dual triggered, two-coil system with high turn ratios and low ohm/high current draw coils will make a difference.

    Eric
    #13
  14. supershaft

    supershaft because I can

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    I have two .7 ohm Dyna coils on my duel plug setup for just that reason.
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  15. supershaft

    supershaft because I can

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    I have two .7 ohm coils on my dual plug setup for just that reason.
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  16. mattcfish

    mattcfish R90X

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    I never said to put a single brown coil on an airhead. You use 2 of those for dual plugged bikes. You use a single green coil on a stock bike. Trust me.
    #16
  17. ericrat

    ericrat Long timer

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    Apparently, I can't read. Apologies.
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  18. England-Kev

    England-Kev Long timer

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    I use a single Brown coil on my Standard 1983 R80ST, as specified by Mottorad Elektik.

    GREEN coils have 3 ohms primary resistance, Single coil for 1970 - 1980 models with points.

    BROWN coils have 1.5 ohms primary resistance,for 1981 through 1995 Airheads with EARLY, SMALLER ignition module and single plugs.

    http://www.motoelekt.com/ignition.htm

    :deal
    #18