APE's TECH BRIEFINGS..
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A high performance ignition coil helps engine performance four important ways. First, the higher voltage allows for a larger spark plug gap, which results in a more robust initial flame kernal at the start of combustion. The result is a real-world engine torque increase. Second, having more voltage on tap means the voltage required to bridge the spark plug gap gets there faster, leaving less time for voltage diversion through the spark plug’s inevitable carbon deposits. Third, the higher voltage potential creates a stronger “push” on the electrical stream to the plug, resulting in increased electrical current, i.e. more energy, more snap. Fourth, with more voltage available, there is more in reserve for non-standard situations such as two-up riding while going uphill on poor fuel on a hot day with too low tire pressures and a 20 mph headwind.So Much Voltage?
This last thought brings us to the subject of how much voltage is commonly used by the spark plug. The fact is the voltage needed to bridge the plug’s gap is not constant but always changing, and is nowhere near the level of the ignition coil’s voltage output potential. That is, a 60,000 volt ignition coil only fires its spark plug at 60,000 volts when it has high demand(load) increased rpm and cylinder pressure , but more often at 7,000-20,000 volts at idle and light demand. How can this be, and why the extra then? When a spark plug is about to fire, what happens is the air inside its gap is of course not conductive and must be made so. It is actually temporarily made conductive, and this is called by a fancy name that has to do with atoms and such, “ionization.”. It simply means that the air is prepared to flow electricity. Think of it as the air molecules getting so heated and excited by the rapidly building plug voltage that the result is voltage can flow through this agitated air to jump the plug’s gap. How much voltage is required to make ionization happen depends on several things ranging from the amount of cylinder compression (pressure) to how worn the plug’s electrodes are. But in round numbers you will be safe to think 5,000-7,000 volts at idle. As soon as the throttle is used however this goes up, and if the transmission is put into gear then load comes into the picture and the requirement goes up even more. So let’s settle on about 15,000-20,000 volts for a bike in a state of cruise. Now go uphill and the requirement increases. Be in too high a gear for conditions and it increases. Yank the throttle open hard and it increases. Go downhill and it decreases, downshift to a lower gear and it decreases. So the actual voltage is all over the place while the bike is being ridden, and higher voltage ensures there is always enough and that it gets there fast.