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I was curious to know what the primary ignition circuit voltage is on a modern Corvette engine like the LT1. It must be some type of capacitive discharge system, so I am guessing that it is in the neighborhood of 100 volts, but that is just a guess. I am sure the experts here have a factual answer.
The ignition coil is fed by two voltages. A constant +12V from the ignition relay and a switched low voltage reference signal that is sent to each coil from the ECM. Here is a schematic from the GM FSM showing the ignition circuitry.
From the placement of the primary coil I am assuming the circuitry is more like a simple transistor ignition where a transistor or maybe an SCR is used to switch the +12V to ground. Since there is a single coil per cylinder the coil has plenty of time for the coil to charge so the there may not be any need to have a more complex CDI circuit. Thus the primary voltage is a switched 12V with the high voltage being generated by the windings in the coil instead of discharging a capacitor on the primary side of the coil to generate a higher primary voltage.
Excellent. Thank you Bill. It makes sense too since each coil has gobs of time to fire its own cylinder. One thing that seems strange to me, though, is when I compare this to the ignition on my 2015 Honda 500cc one-cylinder ATV. That coil has just as much time to build a field as do the coils on the LT1, but the Honda has capacitive discharge ignition that sends 100 volts to the coil primary circuit. Not sure what Honda gains by having that extra complexity. Honda isn't known for adding parts for the hell of it, so they must have perceived some type of benefit.
Last edited by ClothSeats; Feb 28, 2020 at 04:01 PM.
LT1 primary ignition voltage
