>>13755891You mean the sparkplugs? That varies by car.
Most modern systems are computerized. Some form of transformer steps the voltage to whatever is required by the sparkplugs, and energy is stored in a capacitor, then discharged on command by the computer. That's a big part of the reason why modern engines can dynamically (de)tune themselves based on temperature/strain/fuel. The computer can change timing and duration of the sparks. How that timing is calculated depends on the engine.
Old cars had spinning magnets. Magnet would go past a spot, generate an impulse because of the change in the magnetic field, and that would generate a spark. See that a lot on single cylinder lawn mowers cause it's cheap and really simple. Drawback is you cant change the timings on the fly, and moving parts that wear down and die.
I'm grossly oversimplifying stuff here, but short of just copying a wikipedia article that's the general gist of it.
