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In article >,
Matt Whiting > wrote: > > The rotor air gap increases firing voltage. > > How so? An ignition coil does not normally output maximum voltage, but will if the resistance in the secondary circuit is increased, creating a gap that can be jumped essentially is an increase in the circuit resistance, since there is a gap between the rotor and the cap contacts, the firing voltage realized will always be higher than if there is no gap such as with DIS. I may also be wrong on this, but my observations on my ignition scope reveal that firing voltages on conventional ignition systems tend to be a few KV higher than firing voltages on DI systems. > > Comparing spark patterns on an ignition scope, the DIS voltages > > (all else being equal) are lower, lower ionization voltage and > > lower voltage across the plug gap compared to a distributor type > > ignition system. > > An old tow truck drivers trick when trying to start a stubborn > > engine in the winter is to pull the coil wire slightly loose from > > the distributor cap, this increases the voltage output from the > > coil secondary (greatest gap theory). > > I'm not familiar with this theory, but my EE degree is nearly 20 years > old so maybe I just forgot. Can you explain or provide a reference? The greatest gap theory was authored by Mac VandenBrink in 1965, Mac worked as an EE for many years for Allen Test Products. The only references I know of WRT Mac's theory are on i-ATN, easily found if you're a member. Unfortunately I can not copy them and post them here because all i-ATN posts are copyrighted and doing so would jeopardize my membership standing. I became familiar with Mac's teachings way back in the early 80s when I was a GM dealership mechanic during training on the Allen Smart Scope. |
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