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# [Solved] How many times does a spark plug spark per second....?

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How many times does a spark plug spark per second....?

Posted : 06/01/2021 8:26 am
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A complete combustion cycle takes two revolutions of the crankshaft, so the spark plug(s) would fire 1,000 times in a minute. If the engine used a wasted-spark ignition design, common on simple carbureted engines, the plugs would fire 2,000 times, with every other spark having no effect.

Posted : 06/01/2021 8:27 am
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RPM (base timing) would dictate, for the most part, the amount of times a spark crosses the gap on a spark plug in one minute. With a conventional ignition system at 2000 RPM it should be in the area of 1000 times a minute, roughly 16 times a second with every other revolution of the engine close to the end of the compression stroke (advanced) or just barely into the power stroke (retarded).

I don't recall any carbureted engine using DIS (waste spark type) systems off hand.  The first I remember running into was on port fuel injection.  It does "fire" with every revolution of the engine.  At 2000 RPM it would be around 2000 times a minute or roughly 32 times a second with 2 cylinders (companion/sister cylinders) secondary having a spark plugs in series in that circuit.

RPM, load, and mixture play a part in spark delevery also.  Duration of the spark across the spark plug gap is measured in FT (firing time).  This ranges around 1ms (millisecond) to 5ms.  The FT varies with load (cylinder pressure) and fuel mixture (lean leaning towards the 1 ms range and rich towards the 5 ms range).

One of the things manufactures used early on to pass federal emission stationary tests was to put a park or neutral switch incorporated into the ignition/fuel system.  This allowed the "timing" to be retarded to produce less emission out of the exhaust.  Less cylinder pressure (les NOx), less emissions, and with some a smoother idle.

This post was modified 3 years ago by The Engineer
Posted : 16/07/2021 3:03 pm