What coil to use with chrome box?

[RJRENTON]

Well actually you would get a higher voltage spark without the ballast resistor since you would have
12 x turns ratio Vs approximately 9x tunsvratio.
But it may not have much longevity.

The higher turns ratio also affects the inductive reactance (more wire the higher the inductive reactance), which is the coil's ability to charge and discharge, to produce the spark. Remember that the higher turns ratio also develops higher reflected induced primary voltage that the ECU's switching transistor must be able to withstand. The spark generated by the coil occurs when the switching transistor turns OFF not on. The inductive reactance of the coil influences the rate and time at which the coil charges and subsequently discharges. Just talking out loud...
BOB RENTON

 

[Geoff 2]

The coil may or may not require a ballast resistor. Always check with the maker.
If a bal res is reqd, the coil is designed as a system to be used with it & provide the correct electrical properties for max output.
- using a coil with bal res that was not designed to be used with a BR will reduce spark energy.
- using a coil without a BR that was designed to be used with a BR will overheat the coil & it may fail. In the short term it may provide more spark, but the windings are copper which will heat up, increase resistance & could actually reduce spark energy due to the increased resistance/reduced current.