Posted by John T on September 17, 2014 at 05:48:45 from (216.249.72.121):
Yo dr, Ive returned from my Wisconsin and Minnesota RV trip and have time to post a final comment on your 6 volt and 12 volt ignition coil question:
1) One limiting factor in old Kettering Ignition points ignition systems is how many amps the points can switch before they burn up prematurely, and that's around 4 amps or less.
2) Therefore, a 6 volt coil has around 1.5 ohms of LV Primary winding resistance (I = 6/1.5 = 4 amps) while a 12 volt coil has around 3 ohms of LV Primary winding resistance (I = 12/3 = 4 amps)
3) Regardless of a 6 or 12 volt coil, the HV Secondary voltage ONLY rises high enough to arc jump current across the spark plug open gap which may be say around 7,000 to 10,000 volts depending on gap thickness and compression and fuel.
4) Therefore, the coil firing voltage REGARDLESS if a 6 or 12 volt coil is used, given the exact same parameters IS THE SAME. (and is the same even if you used a so called super duper high voltage 50,000 volt coil, they may have the "capacity" to achieve a higher if necessary firing voltage, but they only rise high enough to fire the plug)
SPARK ENERGY:
5) A 6 volt coils LV primary instantaneous power when conducting is 6 x 4 = 24 watts while a 12 volts coils LV primary instantaneous power is twice that or 12 x 4 = 48 watts (either still produces same voltage to fire the plug and ignite the fuel air mixture remember)
6) The ENERGY which gets expended across the plugs gap when it fires is a bit less (heat losses and inefficiencies) then the energy which was stored in the coils magnetic field when current stops (points open) and its dissipated in the form of Volts x Amps x Time (sort of like watt hours the utility charges) when current jumps the open plug gap.
THEREFORE even if 6 or 12 volt coil is used, given the same conditions the same firing voltage takes place, and that's a high heat high voltage arcing current release of energy sufficient to ignite the fuel air mixture. HOWEVER if theres more stored energy to dissipate when the plug fires, a higher energy discharge takes place, meaning more Volts x Amps x Time, BUT since firing voltage is the same, theres EITHER more current across the plugs gap orrrrrrrrrr the arc duration may be longer if theres more energy to be dissipated when the plug fires. HOWEVER as long as the arc produces enough heat and energy release to ignite the fuel, if it consists of more current (ie heat) or the arc duration is slightly longer, such may or may not be necessary.........
That's my story n Ima stickin to it. I hope my techy friends like janicholson and JMOR and Soundguy and Bob and Bob M and others will correct me if I'm wrong. I thought I was wrong once but I was mistaken lol
(gonna post on tool talk also as this page goes away pretty fast)
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