What is a Spark Plug?

[Millard]

Spark plug is a device used in gasoline engines to ignite the air-fuel mixture. Its components include: an outer ceramic insulator, a central metal conductor, and internal electrodes. Types of spark plugs include: 1. Standard spark plugs; 2. Projected insulator spark plugs; 3. Electrode spark plugs; 4. Seat-type spark plugs; 5. Pole-type spark plugs; 6. Surface-gap spark plugs. The working principle of a spark plug is: under the control of the engine, it introduces the high voltage electricity generated by the ignition coil into the engine cylinder, creating a spark between the spark plug electrodes to ignite the air-fuel mixture, enabling the engine to operate normally.

[DiAshley]

Spark plugs are like the pacemakers of an engine. These little guys are screwed onto the cylinder head and have to deliver a precise 'snap' of spark exactly when the piston compresses the air-fuel mixture to its maximum. I've seen many cars with poor acceleration or skyrocketing fuel consumption, and when opened up, it's often due to worn-out spark plug electrodes. Standard nickel alloy plugs need replacement every 20,000-30,000 km, while iridium ones can last up to 80,000 km. Last time I changed mine, I found a crack in the ceramic insulator - no wonder the engine was shaking like it was dancing. Oh, and always remember to torque new plugs to specification during installation, otherwise you risk gas leaks or worse, breaking one off in the cylinder head.

[DeSpencer]

You see, for the engine to explode and push the pistons, something has to ignite the gasoline, right? That's what the spark plug does. The tiny electrode gap at its bottom is absolutely critical—I've measured new plugs at around 0.8mm normally. When carbon buildup clogs the gap over time, ignition becomes weak and ineffective. Last time I fixed that old car belching black smoke, replacing it with platinum spark plugs dropped fuel consumption from 12L straight to 9L. Folks having cold start issues in winter should check here first. If electrodes get gunked up with oil residue, a quick spray of carburetor cleaner can serve as emergency treatment. Remember never to remove them barehanded when the engine's hot—getting blistered is pure misery.

[VonCarlos]

As the final executor of the ignition system, the spark plug actually works quite hard. It has to endure explosion temperatures exceeding 2000°C and withstand 20,000 volts of high voltage electricity with every ignition. I've found that plugs with different heat ranges suit different engines—for example, modified cars use high-heat-range plugs to avoid pre-ignition. By the way, that brown trace on the ceramic insulator is actually called a heat line; experts can read combustion conditions from it. If you notice the electrode burning into a rounded tip or the side electrode turning blue, it indicates the engine is overheating, and you should immediately check the cooling system.