If you have a gasoline powered engine that runs, chances are you have spark plugs. While that engine is running there are thousands and thousands of tiny explosions happening inside of a thick block of iron or aluminum, or some other kind of metal, and those explosions happen when spark plugs ignite the compressed fuel mixture in each cylinder. There are different kinds of spark plugs you can buy. Some spark plugs are geared towards performance in the way of creating more power, and others for reliability.
Unfortunately, you can’t just stick any old spark plug into any engine, or rather you shouldn’t. Spark plugs are carefully made to resist a certain amount of heat and are gapped to specific measurements in order to create a specific-sized spark. Each engine is made differently, where the stroke (or distance each piston travels) is carefully measured and timed, and that affects the compression, which is followed by ignition. In other words, spark plugs are built to accommodate specific engines.
For instance, Ford recommends using Motorcraft spark plugs in its cars because they accommodate the specifications of their engines. NGK branded spark plugs are recommended for just about every Japanese car, but there are different materials for different engine manufacturers. Platinum spark plugs work in a Nissan 240sx, but you need to get plugs with the correct gap. In order to properly replace spark plugs, find out from the manufacturer of your engine what kind of spark plug they recommend, or some cars will have the information in the owner’s manual.
Typically, engines have one spark plug for each cylinder, but depending on which car you own it could have something called dual ignition. If you have dual ignition, there are two spark plugs used per cylinder, which means you'll need eight spark plugs on a four cylinder engine.
On the other hand, rotaries are a special breed of internal combustion because they don’t use cylinders but still use spark plugs to ignite the fuel mixture. Rotaries use as many spark plugs as there are rotary assemblies. Mazda’s 13B Wankel rotary engine, for instance, is two rotary assemblies bolted together so it uses two spark plugs.
You can replace your own spark plugs, but depending on what car you own it can be incredibly easy or incredibly difficult. For example, in a Nissan 240sx, each spark plug is accessible from the top of the engine so it’s relatively easy. In a Subaru BRZ or Toyota 86, because of the car’s design and where the engine sits, in order to replace the spark plugs you must lift the engine several inches. This involves unbolting the engine from its mounts and suspending it somehow.
Take extra care if you are replacing your spark plugs. Triple check which kind you’re getting, and make sure they are the correct ones for your engine. If they’re wrong, it could cause a catastrophe.
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