<VV> Coil volts

[JVHRoberts at aol.com]

Not exactly. The ballast resistor is to limit the current to the coil at  low 
speeds, and with the key on, engine not running, points closed. A  
conventional breaker point ignition uses less current as RPM rises, and more as  it 
falls. Without some means to limit the current, you'll fry the points and  coil in 
short order, and as such, a serious compromise had to be struck. The  bypass 
circuit is to increase ignition  ENERGY while cranking, but this is  a brief 
event. 
Transistor ignitions take care of this by having a fixed 'ON' time, no  
matter what the engine speed. Typically, factory electronic ignitions draw more  
current as the RPMs rise. As such, they can saturate the coil as much as needed, 
 and no more, no matter what the engine speed. 
 
 
In a message dated 8/13/2005 12:47:24 PM Eastern Standard Time, pp2 at 6007.us  
writes:

>the  coil hot side should receive a full 12 (or whatever the battery  tests  
>at)
>minus a little bit for wire runs, during cranking, since  the full  voltage
>should be supplied via the starter solenoid.  When the starter stops, and  
the
>engine runs, it should drop to  about 9-10 volts.

Well not quite. The reason the ignition is designed  for 9-10 v is when the 
starter puts its load on the system (a BIG load),  the voltage is going to 
drop considerably but not below 9 v. So by  designing the ignition for 9 v 
you have the hot spark needed for starting.  After the engine starts and the 
starter disengages, the charging system  returns to normal so the resistor 
is necessary to keep from overdriving  the coil.

Transistor ignitions usually perform this juggling act  internally so no 
ballast resistor (which is really just wasting power) is  necessary.

Padgett