block diagram The above block diagram shows the test equipment configuration for the following measurements. primary coil voltage primary coil current primary coil dwell coil spark duration bench test configuration Power Supply 13.8 volts Current Shunt .1 ohm Test Diode 1N4007 Test Capacitor .47ufd @400v Spark Plugs 2 @ gap .060” each Plug Wire Resistance 26K ohms total oscilloscope measurements Scope Upper Trace Spark Duration  1ms (.5ms/div) Primary Coil Voltage 357.5 volts (20v/div) Scope Lower Trace  Coil Dwell  1.7ms (.5ms/div) Primary Coil Current 4 amps (.1v/div) Click image to enlarge.
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The test in the video below simulates the spark gap and gas ionization similar to what would be present on the compression stroke of an engine. This test requires higher voltages than typical conditions of a Fairmont engine proving the performance of the buzz coil. The test configuration consists of a series circuit using 2 resister spark plugs gaped at 0.060” each at a pressure of 95 psi. The following 2 videos are open air spark gap tests that give a visual representation of the performance of the DX ignition. The conclusion of this test shows the ability of the buzz coil to ionize the air at atmospheric pressure and jump a gap of 1” while maintaining enough heat to give the spark a horseshoe effect. The sound is from the air collapsing around the spark. When the basic fundamentals of a spark are understood the advantages of DX ignition are clear. The following information is an attempt to briefly explain the primary components of a spark. Spark Composition 1. Breakdown voltage is the voltage required to initiate a spark between two conductors known as a spark gap, one of the basic principles of a spark plug. The maximum available voltage of an ignition coil is typically advertised at 40kv or greater which is important to consider, however it should not be the only factor when selecting an ignition system because voltages required to initiate combustion are typically significantly less and rarely approach a peak or maximum value. To determine the actual voltage required to jump a spark plug gap in a running engine there are many conditions to evaluate.  Compression ratio- High cylinder compression requires higher ignition system output voltage. This generally is not an issue with Fairmont engines as they are low compression between 60-80 psi. Fuel Mixture- A lean or rich fuel mixture adjustment correlates directly to the coil voltage required. A lean mixture requires higher voltages and causes spark duration to become shorter. This condition places considerable stress on the ignition and often causes misfires on a poor performing buzz coil. Spark Plug Gap- Plug gap is often overlooked or set to an arbitrary value with out giving consideration to the ignition system as a whole. A wider gap generally promotes better performance due to the increased flame kernel, however a higher voltage is required. As the gap increases the spark duration will decrease because a stock buzz coil can only supply a defined amount of energy. Ignition Timing also changes ignition voltage requirements. If the timer lever is adjusted to fire when the engine cylinder pressure is the highest near piston Top Dead Center, higher ignition voltages are required. 2. Ionized Gas occurs from the spark that was created by exceeding the breakdown voltage. The ionized gases provide a low resistance path in the spark gap for the ignition energy. It is the disrupted nitrogen molecules in the ionized gas that give the spark a blue or violet glow. The color and intensity changes with respect to ignition output energy. 3. Flame Kernel envelope contains the heat and UV radiation necessary to initiate fuel combustion. The more available energy supplied by DX ignition the faster and farther the energy propagates into the cylinder increasing efficiency and performance. An interesting topic for discussion is why Fairmont used a buzz coil rather than traditional automotive ignition, such as Kettering, that was available during the same era. It is likely buzz coils were originally used because the ignition power source for motorcars was commonly dry cell batteries which was a simple and reliable option compared to the more complex and costly systems with generators. A traditional buzz coil only consumes power when it is cycling and producing a spark. Other decision factors may include long dwell times if a Kettering ignition system was used. Fairmonts only fire one time per engine revolution which means the ignition coil would consume energy approximately 92% of the time. This would cause excessive heat in the coil at low RPM’s and also waste energy.