Originally Posted by DazC
Originally Posted by JesseT
Other end is the constant +12V (black wire) and the other is the ignition live (green wire). At crank speed (~200rpm) a spark is given each 300ms. When you compare this with a common coil dwell time of ~5ms, you would see that at average the ignition live is only a few tenths of a volt short of the battery voltage.
tabetha, the coil ratio is not that important as it first seems. Remember that several tens of kilovolts are easily acchieved even with common coil ratios of less than 100.
The green wire isn't ignition live. The black wire is ignition live. The reason why you will find voltage on the green wire is because it's not been earthed yet.
Pardon my english, live was a badly chosen word. I meant the green one anyhow whatever you call it. My point was that at cranking speed it's earthed for such a small amount of time each time that a multimeter won't read anything.