Internal Combustion Engine Fundamentals. McGraw-Hill, Schwaller, Anthony. Motor Automotive Mechanics. Delmar Publishers, Davis, Marlan. February, October 17, May, Toggle navigation. To make spark plugs, manufacturers first extrude or cold-form steel to the proper hollow shape 1. Periodicals Davis, Marlan.
Other articles you might like:. Also read article about Spark Plug from Wikipedia. User Contributions: 1. If a piece of spark plug ceramic was suspected of having 'fallen' into an engine combustion chamber, would it be ok to run the engine or would further inspection and removal be order of the day?
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Message Regarding Your Privacy. I accept Submit Submit. Powering Your Vehicle Necessary to start any gas-fueled combustion engine, spark plugs send high voltage electricity to one end and ignite a spark at the other end. What is the design of a spark plug? Connects to the ignition system and conducts the high voltage to the central electrode. Central Electrode. Ground or Side Electrode. Hex Head. Located between the insulator and the housing, it helps keep combustion gases from escaping.
Helps stop voltage from jumping to the hex head. How do spark plugs work in my engine? This is no laughing matter: If the plug isn't cold enough for a particular application, it can't get enough heat out of the piston chamber.
This can lead to pre-ignition, knocking, and permanent engine damage. If you aren't sure which spark plug heat range to use, err on the side of using a plug that's too cold rather than a plug that's too hot.
Hot plugs have more insulation and are found in most standard engines. The extra insulation keeps the plug's temperature high enough to burn off carbon deposits, which allows for more time between spark plug changes. As gas prices climb higher, more manufacturers are claiming that swapping out old spark plugs for their premium plugs will boost any car's gas mileage. This is true -- but only to a point. The fact is, dirty, carbon-fouled, misfiring spark plugs will definitely lower a car's fuel economy and replacing them with shiny, new plugs will definitely improve fuel economy.
Whether those plugs have exotic metals or nickel-alloy center electrodes doesn't matter quite as much as having the appropriate heat rating and gap between the center electrode and the ground electrode. Speaking of those gaps, almost any plug you can find at the auto parts store will come pre-gapped for your engine.
The days of setting the gap with a gauge are pretty much over, unless you're squeezing every last bit of performance out of your Saturday night hot rod. Engine modifications often mean you must gap new spark plugs, but stock engines with factory-approved, pre-gapped replacement plugs can usually go without adjustment.
Now that we know how a spark plug functions in the engine and the materials they're made of, let's find out what's inside these little guys. There's some debate about who invented the spark plug. One of the earliest possible versions was invented by an African-American named Edmond Berger, reportedly in February Skeptics cite the scarcity of internal combustion engines in , which would make Berger's invention more experimental than practical.
At the top of the spark plug sits the connector , or terminal. This is where the spark plug wire attaches. The terminal connects inside the plug to the copper core of the center electrode, which is surrounded by insulation. Next comes the hex head. This is where the socket wrench fits for tightening and loosening the plug in its hole in the engine.
Just below this is a gasket that compresses tightly against the cylinder head. It's also known as a crush washer or the seat. Some plugs have a tapered seat, without an additonal seal.
These are generally used in iron cylinder heads, while plugs with gaskets are usually found in aluminum cylinder heads. The bottom half of the plug is threaded. This is the part that gets screwed, gently yet firmly, into place. A tiny bit of the center electrode juts out of the plug's lower end. And the whole thing is capped off with a ground electrode or ground strap. The spark that makes the engine run jumps the gap from the very end of the center electrode to the ground electrode.
This is what ignites the air-fuel mixture that's been compressed by the piston. The ground electrode is made of metal, with options ranging from stainless steel to titanium. It can come in several shapes as well, from notched or Y-shaped electrodes to triple electrodes with three little arms that seem to reach for the tip of the center electrode.
As far as materials and shape of the ground electrode are concerned, you pretty much get what you pay for. High-end spark plugs made with exotic materials will cost more, but they'll also deliver better conductivity and spark. Diesel engines use something called glow plugs rather than spark plugs. Diesel engines don't require spark plugs, but they do start more easily if the air in the cylinder is warm.
That's where the glow plug comes in: It looks a lot like a spark plug, but instead of a center electrode, it has a heating coil that heats the combustion chamber. Typically, the appropriate firing end temperature is approximately , degrees. Below degrees, carbon fouling is possible. Above it, overheating becomes an issue. In terms of operation, the spark plug is connected to the high voltage generated by an ignition coil by way of a conventional distributor or by way of an electronic means.
As electricity flows from the coil, a voltage difference develops between the center electrode and ground electrode on the spark plug. With a spark plug removed from the cylinder head and properly grounded to fire, you can hear a definitive click. If conditions are dark enough, you can see the spark. The click you hear is essentially a miniature clap of thunder, and the spark you observe is similar to a miniature form of lightning. Within the combustion chamber, the intense heat created by the spark plug creates a small fireball within the gap.
In terms of construction, spark plugs may not be quite as simple as you think. In fact, they are precision pieces of equipment. Thanks to the folks at Champion Spark Plug, we can provide you with a complete breakdown of the various plug features. Keep in mind that the vast majority of spark plugs offer similar although not necessarily identical construction.
In the accompanying photos, you can see what many of the above spark plug features actually look like.
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