Info on FBO ecu unit

@Mattax
About HEI coil current limit. It works by turning off coil drive transistor when current exceeds set limit, and back on when current is under limit. Switching happens in fast repetive manner, such that resulting current is smoothly regulated. It takes only one small transistor, and a low value shunt resistor in coil drive emitter to ground connection. The small transistor collector pulls down the drive transistors base input signal, over ridding normal control. Resistance of shunt resistor is about 1/15 of ballast resistor, and drop of only 0.65V vs 6V with ballast, however drive transistor does dissipate additional energy, when in current limit.

Based on my ignition development work, with proper dwell control, current limit action only happens when cranking, and unstable low RPM below idle speed.