Ramblings from the Old, the Bad, and the Ugly
1......Changing from a conventional factory type coil to one which "does not need" a ballast is a DOWNGRADE
2......Just about all US 12V cars used the ballast system, and here is WHY. The ballast / coil combo was designed to run as the car was going down the road with the system at 14V. This provided a varying voltage to the coil, depending on RPM, of some 8--11V plus or minus.
But when STARTING, battery voltage can sag way down, especially in winter, left the lights on, or both. So a BYPASS circuit connects the coil direct to the battery during "crank," and so you STILL have 10V or so at the coil for starting........a hot spark
If you use an "internal ballast" coil or one which does not need one, you lose the cranking bypass
3.......If you use a factory equivalent coil and ballast as in "original" and you use a Mopar 4 pin ECU you do not need to change anything. You will see the diagrams RE: the 5 pin box and 4 pin resistor. Unless you get an older Mopar ECU out of a junk yard, you will NOT have a 5 pin box. You cannot tell by looking. Many aftermarket, replacement boxes have 5 physical pins. If you don't know what you have, you must "ohm" the 5th pin to the others to determine if it goes anywhere.
4.....If you use a GM HEI module, you can use a factory coil and eliminate the ballast, and gain some ground with a hotter spark. This is the one case where the bypass circuit "does not matter." The reason is because of the way the HEI works. It "fires" the coil "harder" and produces more spark. I use a 30? year old factory coil on my Dart with an HEI, and it works just fine.
