Telling the difference between DC and AC sparking coil

[veloduke]

To achieve that, it would be best to start with as many volts as possible at the input, aka the primary winding. So, since V= I/R (from Ohms law, I = V/R), to get maximum volts in the primary winding we need to either increase the current or decrease the resistance.

I think you have made a mistake here. Ohm's law is V=IR.

Two different coils with different resistances; to get the same power out from each, we could use the formula W-VxI (power = volt x amps).

So if you increase the voltage, you will need to reduce the current to maintain the same power out.
AC ignition generates more voltage to the coil primary, so to reduce the current you will need to increase the coils resistance (thinner wire, more turns,...).

Well, that's how I understand it

[mrkprsn]

I got this info from the other site I don't like as much.

Originally, the AC coils had a green sticker against the DC ones a red sticker. Then later on again they moved to stamping the bottom of the coils. AC in Italian = CA (corrente alternata), DC = CC (corrente continua).

I checked ono of my "4 ohm" coils and sure enough 6Vca was stamped on it.

DucatiRedGreenLabelCoils.jpg

[Ventodue]

I think you have made a mistake here. Ohm's law is V=IR <snip>

Well, ain't I the clown! Thanks for pointing that out, Max.

Back to skool for me ...