Ignition Coil Circuit Simulation By Bowling & Grippo

This program simulates a conventional automotive ignition circuit, and shows you primary coil current, secondary voltage, and energy. This model is for conventional Kettering ignition (i.e points and electronic-switched primary), not the capacitive-discharge type (i.e. MSD and other aftermarket systems).

The inputs are beginning and ending RPM, RPM step, dwell angle in crankshaft degrees, resistance of primary ignition coil circuit in ohms, inductance of ignition coil primary in milliHenries (mH), battery voltage, and capacitance of ignition coil secondary in picoFarads (pF). This model assumes 100% energy transfer from primary circuit to secondary circuit, which will not be the case in the real world - expect 70-85%.

The interesting thing here is to see how the secondary voltage drops off at higher RPM because there is less time to "charge" up the ignition coil primary. You can jack up the dwell angle, which will allow more time for the coil to charge, but then the peak primary current rises at lower RPM, and the more current the more heat generated in the coil, which is not good either (generically, coils like 10 amps or less). Play with the values and see what you can come up with - maybe you can design the next super-duper coil!

Program Inputs:

Starting RPM Value:

Ending RPM Value:

Delta RPM Step:

Dwell Angle in Degrees of Crankshaft Revolution:

Resistance of Ignition Coil Primary (Ohms):

Inductance of Ignition Coil Primary (milliHenries):

Battery Voltage (Primary Circuit Volts):

Capacitance of Ignition Coil Secondary (picoFarads):

Press this button to submit a computation:

To reset the form input:

Bruce A. Bowling
Al C. Grippo Bowling