What is the working principle of spark plugs?

[VanAaliyah]

Spark plug working principle: The spark plug's ground electrode is connected to the metal shell, which is threaded into the engine block via the cylinder head. The insulator primarily serves to isolate the metal shell from the center electrode. The terminal nut is the part of the spark plug that contacts the high-voltage coil. When current passes through the terminal nut and the center electrode, it ionizes the medium between the center electrode and the ground electrode, generating a spark to ignite the air-fuel mixture in the cylinder. Spark plug replacement interval: Under normal maintenance conditions, replacement is recommended after driving 40,000 to 60,000 kilometers. However, this may vary depending on the brand and engine type, so it's advisable to follow the owner's manual. The following standards can be referenced for maintenance replacement: Platinum spark plugs should be replaced at 40,000 km, standard nickel alloy spark plugs at 20,000 km, and iridium spark plugs at 60,000-80,000 km.

[SanSteven]

Spark plugs are like the ignition switch of an engine. Having tinkered in the garage for over a decade, I deeply understand their importance. When the engine operates, the ignition coil generates tens of thousands of volts of high-voltage electricity, which is transmitted to the center electrode of the spark plug. There's a small gap between the center electrode and the ground electrode, and the high voltage can instantly ionize the air in this gap, creating a thunderbolt-like spark. This tiny lightning bolt can reach temperatures of up to 2000 degrees Celsius, perfectly igniting the compressed air-fuel mixture in the cylinder. Each ignition is precisely timed to discharge exactly when the piston reaches the top of its compression stroke. If the spark plug gap is incorrect or severely carbon-fouled, ignition will be delayed, causing the car to shake like it's having an asthma attack. Old-fashioned single-electrode spark plugs use ordinary metals, while many modern vehicles now use iridium alloy spark plugs, which offer longer lifespan and more stable ignition.

[LeGabrielle]

As someone who frequently modifies cars myself, I pay special attention to the details of spark plugs. Their core principle is high-voltage discharge: the ignition coil instantly boosts the 12-volt voltage to tens of thousands of volts, which is then conducted through the spark plug's center electrode. In the 0.6 to 1 millimeter gap at the electrode tip, the high-voltage electrons overcome air resistance, creating a blue-purple electric spark. This tiny explosion precisely ignites the air-fuel mixture, driving the piston to generate power. The design is actually quite meticulous: the ceramic insulator must withstand high temperatures, the metal shell must conduct heat, and the electrode material must resist erosion. Nickel alloy spark plugs need replacement at 30,000 kilometers, while the platinum electrodes in my car can last up to 60,000 kilometers. Spark plugs are most critical during cold starts in winter; worn-out spark plugs can cause ignition difficulties and result in black smoke from the exhaust pipe.

[SavannahLynn]

From my years of experience in auto repair, spark plugs are essentially miniature lightning generators for internal combustion engines. When the engine is running, the piston compresses the air-fuel mixture to top dead center, and the ECU immediately commands the ignition coil to release high-voltage electricity. The current flows from the terminal nut at the top of the spark plug, through the conductive glass seal, and reaches the center electrode. At the electrode gap, electrons violently collide with air molecules, creating a plasma spark with temperatures soaring above 3000K, instantly igniting the air-fuel mixture. Multi-ground spark plugs also feature auxiliary electrodes to ensure stable ignition under various operating conditions. Electrode erosion, carbon buildup, or excessive gap can all affect the intensity of this instantaneous energy release, leading to engine misfires.