Originally posted by Boomyal:<br />
What determines the ohm rating of coils that are chosen for specific applications?
An ignition coil has two distinct windings - primary and secondary. The OHM rating is reffering to the primary winding. A 1.5 ohm primary winding will produce (roughly) 500 volts, a 3 ohm primary winding will produce about 300 volts. As the voltage passes through the secondary windings, it increases 100 fold. As you can see, a 1.5ohm coil is capable of about 20,000v more at the business end of the circuit. But there is a problem, you can't use a 1.5 with points because you would be changing them every half hour, you would turn your distributor into and arc welder. So for points (and early 'dumb' electronics), 3 ohm coils feed with 9 volts (ballast resistor) was the only way to save points. <br /><br />Another reason for 3ohm coils and resistors was to help reduce heat in the coil. <br /><br />Modern manufacturing techniques (with coils) & the introduction of 'smart' electronics allow for the elimination of the ballast resistor. Higher voltages are now possible and the switching mechanism is much quicker and finely controlled. In fact, some car manufacturers are playing around with the idea of 36volt systems.<br /><br />This all leads to one thing - BIGGER spark. In the not so distant future, 0.5 ohm coils will be the norm.IMO.<br /> <br />I find it interesting that a similar senario is currently being played out in the audio industry, manufacturing techniques are allowing lower OHM speakers and amps to be built. some down to 1 ohm, this allows the amp to feed the speakers with more juice.<br /><br />Aldo
