coil question

[mac]

what is the rule on voltage to the coil? i had done some looking around and thought it was safe to use 12 volt to the coil that i am using because of the primary winding resistance (bypass the ballast resistor). what is the rule of thumb on this? running a mopar performance ignition system with the chrome box.

 

[SomeCarGuy]

Depends on the coil.

 

[Big John]

Depends on the coil.

:yeathat:

I think the voltage drops to 5 or 6 volts after the resistor.

 

[zupanj]

I thought that the resistor was supposed to drop the voltage to 9v. When I installed my MSD box the instructions said to hook up one wire to a switched 12v source such as the positive wire from the old coil if it did not come through the resistor which was not the case for me. I put a voltmeter on both sides of the resistor I got 11v in each case so I hooked up to the positive coil wire which came through the resistor. So far everything works fine but I do wonder if I am getting full voltage out of the box. I also wonder if my resistor if messed up but I don't see how that can be from my past experience with them.

 

[69hemibeep]

Depends on the coil.

:yeathat:

I think the voltage drops to 5 or 6 volts after the resistor.

:yeathat: as high as 7v. You can use a length of resistor wire and do away with the ballast

 

[mac]

Depends on the coil.

the coil in question is a msd 8222

 

[Big John]

I just looked at the MSD instruction sheet online and it says you need a .8 ohm ballast resistor if you aren't using their ignition. That makes sense to me. They take power to the coil from the MSD box rather than taking 12 volts from somewhere else... so yea, the voltage to the coil is most likely reduced in the box rather than using a ballast resistor.

http://www.msdignition.com/Products/Coils/Race/8222_-_High_Vibration_Blaster_Coil.aspx

 

[mac]

thats where i went wrong. i have a ballast back on the car now but i will check around for the resistance i need.