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| Joined: | 03-14-2005 |
| Location: | Atlanta, Georgia USA |
| Posts: | 406 |
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The initial assumption is that the spark will fire every time, which simply is not the case. MSD type systems that reach +40K volts and have multiple sparks in their duration are trying to increase the odds of the spark firing.
Of course when/if the spark does strike, it has to ignite the fuel. If the engine is cold and the fuel is poorly atomized, this may not happen (hence the 'multiple' sparks). A larger plug gap also increases these odds, but 'resistance' increases and more voltage & energy is required.
Likewise with increased compression ratios, there is actually more 'resistance' and the spark needs more voltage to jump the gap. Doubly so if the plug gap is widened. Tripple that if the plug is also fouled with carbon.
Once you understand/accept that 3-5% of the time your plugs are NOT firing (on a good day), that's when the choice to adapt a 'high-performance' system makes sense.
Judson