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Coil questions

Discussion in 'Technical and Troubleshooting Torque' started by saintan, Sep 15, 2006.

  1. I got a few questions about coils, hopeing I can get the good info.

    Problem is that I need 2.7 ohm resistance coils, I barely understand this part but original is not available.

    So replacements vary, good alternatives at 2.4 ohm and 3 ohm resistance and a few various bikes have suitable coils.

    Correct me please but help me to understand wtf it all means.

    A resistance ballister before the coil to correct resistance is supposedly bad, why?

    What is the problem with changeing resistance and litterally doubleing it?

    I understand the greater the resistance, the hotter the spark (maybe?) so whats the problem with going say 5 ohm instead of 2.7 ohm?

    Is it just a case of needing colder plugs to deal with extra heat and then plug gap is just trial and error, possibly larger diameter leads? Does higher resistance effect timeing?

    Any info to help me understand is appreciated.

    Side note- WTF has resistance to do with, how is it put in to expanding/collapseing magnetic fields?
  2. Feel free to correct any bum info, but this is what I dug up for any one else interested.

    Ballist resisters should be used, it basically reduces the charge to the coils while the bike is running and only delivers full charge to coils while cranking the engine over.

    lack of a ballist resister can lead to burning out your coil/plugs

    Coil resistance has little relation to final voltage, it's purely a measurement based on wire size/length in the 1st coil windings.

    For example, a 10 mm thick wire 10 mm long has nearly zero resistance while a hair-thin wire 100 metres long has plenty of resistance. So the finer and longer a wire used for the 1st winding gives higher ohm resistance.

    The 1st windings have an electrical charge on and off triggered by your CDI or points, this expands then collapses a magnetic field.

    This magnetic feild is sort of captured by the 2nd windings to produce your spark. The heat of the spark is affected by the differance between the 2X "windings"

    For example, the 1st coil winding has 5 loops and the 2nd coil winding also has 5 loops, this keeps voltage unchanged. (probably dosn't but for the example it does)

    But if the 1st loop had 5 ans the 2nd had 10 windings, voltage is doubled while amperage is lowered. (maybe not exactly doubled but you get the drift).

    Voltage is what allows a spark to ark, the higher the voltage the greater the distance the spark can jump.

    Higher/lower resistance coils do not effect timeing whats so ever, you may not have ample current to power higher resistance coils though unlikely.

    So depending on the out-put of the coil, it will affect what heat-range of spark plugs used, a colder plug has more cooling ability and will be needed for hotter sparks.

    It's also possible thicker leads may need to be used if you have a massive increase.

    So thats the basics of what I could find out, There is supposedly no problem with going higher out-put coils except knowing what plugs/gaps to use.

    Plugs are trial and error, you know if you have the correct heat range plug by the "heat discolouration" on the thread of the spark plug. The blueing effect of heat discolouration should effect around the 1st 3 - 4 threads counting from the sparky end (electrode end).

    If you disagree with any of this, let me know and I'll look into it.
  3. informative reading, but im curious how increasing the voltage would increase output? and increased output is obviously the aim???
  4. Voltage isn't increased, only decreased by the ballast resister dureing normal running.

    Any inductance (think thats the right word) is purely based on the diferance between the 2 coils. (the 2 different coils are interwound but not connected)

    So voltage isn't increased to the coil to get a hotter spark, just more windings are added to either coil to change the ratio between them.

    1st example, 1st coil winding is 1mm wire 100 metres long wound into 200 loops (like a spring). The second coil is the same wire, twice as long with 400 loops.

    2nd example, 1st coil winding is the same but 2nd is twice as long with double the loops.

    For the same voltage applied to both examples, the 2nd will produce much higher voltage.

    I think thats what you were askin?