Iv used those cheap lighters that use a quick spark to ignite the gas, but after a couple weeks they die out. How are the ones in engines so reliable and last for so long?
Furthermore, how can they fire at JUST the right time, thousands of times a second?
Thanks in advance
In: Engineering
the small spark thingi on a cheap lighter works by smashing two crystals together at hopefully just the right time but that means you need moving parts, a spring and all of that needs to be made as cheaply as possible.
spark plugs are just a dumb device that has two contacts at a specific distance so that a spark or a specific voltage will be able to jump across them.
the magic happens in the ignition coil where low voltage thats used all over the car is turned into a higher voltage that to make it able to reliably spark across the gap of the spark plugs.
all of these have zero moving parts so your spark plugs can fire as fast and precise as your control system can handle which thanks to modern electronics means you can easily activate them thousands of times per minute if you want to.
Sparks plugs are connected to the computer of modern cars and the computer times everything in the engine so that they spark at just the right time. They are designed to last a long time.
No moving parts and 100+ years of development means it’s pretty much as good as it gets in terms of anything that will just work.
Lighters. They have worked good enough for 100+ years, they don’t need the precision so no one puts the time in anymore. Loads of moving parts comparatively, people will only pay pennies and no one is in that mad of a rush that they need to fire first time every time.
Clicky thingy has moving parts that wear out. Spark plug has no moving parts. It’s also designed to take the high temperatures in the cylinder.
Others have covered the why, so I’ll mention the what: Modern spark plugs are usually a layer of aluminum-based ceramic (a very good insulator) surrounding a conductive metal. Usually, the spark gap has either copper and iridium, or platinum as the metal conductor part. These are dense, nonreactive metals, so they only wear away very slowly over time. Since this is very old technology, over 160 years at this point, we’ve had a very long time to refine them to be about as good as they can get.
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