What's special about the Porsche coil

[Dr. No]

What's special about the Porsche coil? Don't tell me it's the CDI--I have installed CDI in other vehicles using their stock (or Bosch blue) coils.

[Early_S_Man]

Well, Loren has one opinion ... and Bosch and Porsche offer distinctly different views ...

A direct quote from Bosch CDI testing publication VDT-WPE 125/3 B Ed. 1;

"The ignition transformer must not be replaced by a conventional coil or be connected or tested as such."

Also, the system is never to be tested without a properly grounded-body spark plug connected to the coil!!!

"If BCDI [system] is checked without the spark gap, there is a risk of flashover in the ignition transformer (insulation damage)."

[Lorenfb]

There's nothing really special about CDI units requiring special coils.
Most ignition coils will work with most CDIs given the following:

1. the turns ratio is about 100:1 (anywhere from 80 to 120)
2. the intertnal resistance can be .5 to 5 ohms
3. the inductance can be 1 to 5 millihenries