Reading spark plugs
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==General spark plug info== | ==General spark plug info== | ||
===Description=== | ===Description=== | ||
| − | A spark plug is a device for delivering electric current from an ignition system to the combustion chamber of a spark | + | A spark plug is a device for delivering electric current from an ignition system to the combustion chamber of a spark ignition engine to ignite the compressed fuel/air mixture by an electric spark, while containing combustion pressure within the engine. A spark plug has a metal threaded shell, electrically isolated from a central electrode by a porcelain insulator. |
| − | A spark plug has a metal threaded shell, electrically isolated from a central electrode by a porcelain insulator. | + | |
| − | The | + | The center electrode, which may contain a resistor, is connected by a heavily insulated wire to the output terminal of an ignition coil or magneto. The spark plug's metal shell is screwed into the engine's cylinder head and thus electrically grounded. |
| − | The | + | The center electrode protrudes through the porcelain insulator into the combustion chamber, forming one or more spark gaps between the inner end of the central electrode and usually one or more protuberances or structures attached to the inner end of the threaded shell, designated the "side", or "ground" electrode. |
| − | Spark plugs may also be used for other purposes; in Saab Direct Ignition when they are not firing, spark plugs are used to measure ionization in the cylinders - this ionic current measurement is used to replace the ordinary cam phase sensor, knock sensor and misfire measurement function. | + | Spark plugs may also be used for other purposes; in the Saab Direct Ignition when they are not firing, spark plugs are used to measure ionization in the cylinders - this ionic current measurement is used to replace the ordinary cam phase sensor, knock sensor and misfire measurement function. |
===Operation=== | ===Operation=== | ||
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