So ive had this question for some time: On a standard set up SJ there is one pulse coil to pick up a singnal via a magnet on the flywheel. This singnal is sent to the CDI then to the ignition coil and spark plug. As there is only one ignition coil ( with one possitive and earth lead on the primery circuit) both spark plugs must fire at the same time. One while the piston is coming up ready with air/fuel fixture and the other while its toward the bottom. In automotive we call this waste spark and its common as. The next thing is the bit i dont believe/understand. My 61x flywheel has four visable magnets so this (I assume) must mean the pule coil is picking up four singnals for every revolution. With the waste spark set up this means both cylinder spark plugs are firing 8 times (four per cylinder) for every revolution. Some one please set me straight as im sure this is not the case. Are two of the mangnets in the flywheel not being picked up by the pulse coil?
Voltage is induced in a coil by a change in magnetic flux. Magnets have a north and a south pole on them, and hence to induce voltage the poles have to change form north to south or south to north. So the four magnets will be arranged as N - S - N - S. A N-S transition will induce an opposite voltage to a S-N transition, so the magento will produce 4 voltage spikes but 2 of them will be negative and 2 positive. This is called Alternating Current (AC) and is why you need a rectifier for it to charge your battery. The CDI will only fire on either the 2 negative peaks or the 2 positive ones.
this would make sence. Im going to check out the north/south thing on a spare flywheel I have. :wink:
