Spark PLugs
Road Master
Joined: Jun 2007
Posts: 883
Likes: 2
From: Clearwater, FL
RE: Spark PLugs
Here is some info I found a while back. I'm not sure who the author is but it wasn't me.
SPARK PLUG HEAT RANGE
The "heat range" of a spark plug determines how hot the plug runs during normal operation. If the heat range is correctly matched to the engine application, the plug will run hot enough under normal driving conditions to burn off fouling deposits before they can cause problems. Likewise, the plug will not get too hot and become a source of ignition causing engine-damaging preignition and detonation. If the heat range is too cool for the application, though, fouling deposits may build up faster than they are burned off.
For this reason, always follow the vehicle manufacturer or plug supplier heat range recommendations when selecting a spark plug for a particular application. Two spark plugs may appear to be identical on the outside but have entirely different heat ranges.
There are situations, though, that may require a slightly hotter or colder plug than the one normally recommended. Switching to a slightly hotter plug can help reduce fouling in an older engine that uses oil, for an engine that spends a lot of time idling or is used for short trip stop-and-go driving. But a hotter plug should not be used unless an engine is experiencing a fouling problem because of the increased risk of preignition and detonation.
For performance applications (racing, or engines that are run under heavier than normal loads or at high rpm for sustained periods of time), switching to a slightly colder plug can minimize the risk of preignition and detonation. Even so, a colder plug can increase the risk of fouling with extended idling and low speed operation.
Many of today's spark plugs have a very broad heat range because the plug manufacturer uses a copper core or platinum center electrode. Copper is an excellent conductor of heat, so the insulator can be designed to run hotter and burn off fouling deposits without it getting too hot under increased load to cause preignition or detonation. A solid platinum center electrode will also carry heat away from the tip, but not if the electrode only has a platinum tip.
The "heat range" of a spark plug determines how hot the plug runs during normal operation. If the heat range is correctly matched to the engine application, the plug will run hot enough under normal driving conditions to burn off fouling deposits before they can cause problems. Likewise, the plug will not get too hot and become a source of ignition causing engine-damaging preignition and detonation. If the heat range is too cool for the application, though, fouling deposits may build up faster than they are burned off.
For this reason, always follow the vehicle manufacturer or plug supplier heat range recommendations when selecting a spark plug for a particular application. Two spark plugs may appear to be identical on the outside but have entirely different heat ranges.
There are situations, though, that may require a slightly hotter or colder plug than the one normally recommended. Switching to a slightly hotter plug can help reduce fouling in an older engine that uses oil, for an engine that spends a lot of time idling or is used for short trip stop-and-go driving. But a hotter plug should not be used unless an engine is experiencing a fouling problem because of the increased risk of preignition and detonation.
For performance applications (racing, or engines that are run under heavier than normal loads or at high rpm for sustained periods of time), switching to a slightly colder plug can minimize the risk of preignition and detonation. Even so, a colder plug can increase the risk of fouling with extended idling and low speed operation.
Many of today's spark plugs have a very broad heat range because the plug manufacturer uses a copper core or platinum center electrode. Copper is an excellent conductor of heat, so the insulator can be designed to run hotter and burn off fouling deposits without it getting too hot under increased load to cause preignition or detonation. A solid platinum center electrode will also carry heat away from the tip, but not if the electrode only has a platinum tip.
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