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Concerning variacs and chokes. I've handmade one of each using MOT primary wire. The variac has about 120 turns on a 4.5" toroid and the choke is wrapped on a 7/8" piece of threaded rod, 15 turns per inch over 10" length for a total of 150 turns. The resistance of this wire is so low I used tin-coated steel tangs that give me a R drop of about .7 ohms per tang.

The problem I'm having is getting them to work for my application. Basically I want to run the current from my truck's ignition module through the choke primary, and the secondary output into the ignition coil, to step the HV in the coil up super-duper. I tried this with the variac initially and got no signal out. I called a variac manufacturer and they said I was getting no action because a coil needs to have a broken magnetic path to "ring," hence they said I needed a choke instead.

As you probably know, an ignition module delivers current continuously and then shuts off abruptly, causing a train of HV oscillatory spikes that diminish/trail off in amplitude/strength.

So now I have a variable choke as described. Problem is, I tried running both AC and DC pulses from a signal generator, 0 - 200khz, 0 - 17V through the primary and can detect no measurable anything at the primary terminals or secondary output. (I also tried the same on the vehicle @ 12V and approx. 8 amps.)  I get nada. It's as if the wire is acting as a dead short. I know I've got continuity because I get the R values mentioned when I measure them, but when I drive the coil, no V
drops. I'm confused and discouraged. Do you have any insight what i might be doing wrong? Thanks

-- thrival57