I have an HEI ignition coil w/ primary resistance of .4 ohms (aftermarket coil, my stock gm measures 1.0 ohm), as measured the inductance on the primary is 9.47mH. I want to use a NPN darlington. If my Vcc is 12v, how do I know what the voltage will be when the mag field collapses so I know what npn darlington to use. I see the ST bu941zt w/ the zener diode that clamps at 300v min. but dont know how to know if it will work...how do I calculate that? I know it will be about 300-400 volts but dont know how to calculate this or find out how to do this? I know 12v/.4ohms = 30 amps but the ST bu941zt cant handle this for collector current.

Suggestions?

Thanks for your help.

Val.