Charlie Cheap":3a2i2oyc said:
Don't forget, if 15,000 volts ignites the mixture, 50 bazillion volts is not needed.
This is a not the total picture and leads to misconceptions.
Looking at the spark waveform on a scope shows a high voltage spike that initially jumps the plug gap.
Once the air between the gap is ionized by the initial spark, the gap resistance goes very low which drops the voltage to a low value and raises the current significantly.
It is the current that ignites the fuel and starts the flame front
Not the Voltage
The more current the wider the spark and the more fuel molecules get targeted.
This is especially important to those that want to run a lean mixture at cruise to maximize fuel economy.
As the engine load and cylinder pressure increases the resistance between the plug gap increases which requires a higher voltage to initially jump the gap.
The ignition system needs to supply enough voltage to jump the gap at the engines highest cylinder pressure.
This also includes the gap between the distributor rotor and the cap which can be as high as 5Kv.
If the rotor phasing is off the voltage needed will be much higher.
In the case of the MSD, a capacitive discharge to the coil may be shorter than an inductive discharge but the current at the plug gap is much higher by several times in comparison to the standard street inductive system.
Another consideration is that the coil discharge time or spark duration decreases as output voltage increases so going to a system without a distributor cap and rotor eliminates the rotor gap which decreases total output voltage from the coil and increases spark duration and spark current.
This is a short pitch for coil near or coil on distributorless ignition systems.
In all the cases so far the 300 six shows improvement in both low end power and fuel economy using the MSD ignition.
Again we are talking about improvements below 2500 rpm.
The use of solid copper wires can cause a crossover spark to another cylinder if the wires are parallel and close to each other.
Been there with resulting piston and valve damage.
Better to use a low resistance spiral wound wire.
If a person wants their Ford six to have better torque throughout the power band with better fuel mileage and less carbon deposits then Yes, a modern ignition system that provides much higher spark current is needed.
The fact that the points are in the glove box kinda negates part of the argument.