Stu Brennan wrote:
>
> The stock ignition system shorts out the ballast resistor to provide a
> hotter spark when the starter is dragging the system voltage down. Do these
> "12V" coils have a similar feature? Or are they so "hot" that they still
> have plenty of energy when running on reduced voltage? I assume that this
> would apply only to a "points" or Pertronics type system, not a fully
> electronic one.
>
> Stu
Stu,
That explanation of the ballast resistor is a little off. Yes, in the
"start position" the resistor is by-passed and a full 12 volts is
applied to the coil during cranking only. This provides a hotter spark
during start. With the modern 1,000 cranking amp batteries, I do not
believe that the system voltage is noticeably lowered. My voltmeter is
at 14.4 volts during cranking. However, during the run position, the
starter is out of the circuit, and the resistor is in, reducing the coil
to about 9 volts. This prevents overheating the coil, as well as
reducing arcing at the points,
You may be correct in the days of 500 starting amp batteries, but better
are now available. British cars have not, to my knowledge, over 50
years, ever used a resistor in the start circuit, and only used 12 volt coils.
The ONLY reason Pertronix ever gave for using a resistor type ignition
coil is to reduce the switching current to within the capacity of the
Pertronix (I) semiconductors. The Pertronix II is a good deal more
robust in this area, and can switch the full amperage of a 12 volt
system continuously. Capacative discharge systems have used 12 volt
coils for a long time, even with points, Unilights, whatever, as the
current through the switching element is significantly reduced to
activating the high energy solid state switches that pour the fast rise
capacative discharge to the coil, directly.
Steve
Steve Laifman < Find out what is most >
B9472289 < important in your life >
< and don't let it get away!>
<SLaifman@SoCal.RR.com>
<http://www.TigersUnited.com/gallery/SteveLaifman.asp>
_/_/_/_/_/_/_/
_/ _/_/_/ _/_/_/ _/
_/ _/ _/ _/ _/ _/ _/_/_/_/
_/ _/ _/ _/ _/ _/ _/
_/_/_/_/_/__/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
_/
_/_/_/
|