The heat rating of each NGK spark plug is indicated by a number; lower numbers indicate a hotter type, higher numbers indicate a colder type.
You can work out whether you need a hotter or colder plug by looking at the current ones. If the current plug is too hot then the tip may be melted or deformed. If the plug is too cold then you may have excessive build up (which can also be caused by burning oil or a rich air-fuel mixture).
To make it easy for you to see the heat range of your spark plug, the number is printed into the plug's part number. Here is how it works. The smaller the number, the hotter the plug. Plugs with a “7” heat range are hotter than “8” plugs, which are hotter than “9” plugs.
Blisters on the insulator tip, melted electrodes, or white deposits are signs of a burned spark plug that is running too hot.
Typically the heat range for NGK Spark Plugs varies from 2-11. This number indicates the thermal characteristics of a spark plug, or how 'hot' or 'cold' a spark plug is.
The heat range of a spark plug is the range in which the plug works well thermally. The heat rating of each NGK spark plug is indicated by a number; lower numbers indicate a hotter type, higher numbers indicate a colder type.
If you use too cool of a spark plug that doesn't heat up to the proper temperature, it won't be able to burn off the carbon deposits, which can cause premature fouling. A fouled spark plug can lead to misfires and engine stalling.
A spark plug is said to be "hot" if it is a better heat insulator, keeping more heat in the tip of the spark plug. A spark plug is said to be "cold" if it can conduct more heat out of the spark plug tip and lower the tip's temperature.
You have selected a plug with a hotter heat range than that recommended. The effect of this in the long run would be burnt out valves and erratic working of the engine. Continual use would cause permanent damage to the engine. If you like your car, get the original spec spark plug.
The lower the number, the colder the plug. Starting with part # 24 (heat range 4), if you want a colder plug you would use part # 23 (heat range 3), for a hotter plug you would use part # 25 (heat range 5).
Some manufacturers numbering systems are opposite the other - for Champion, Autolite and Bosch, the higher the number, the hotter the plug. For NGK, Denso and Pulstar, the higher the number, the colder the plug.
Reeves emphasized that the heat range rating of a copper-core spark plug and an iridium plug will be the same and that it is the tip (overall) length of the center ceramic that determines any plug's actual heat range.
The biggest problem is that running a colder plug when it isn't needed, is that it will foul up quickly. This happens because the plug tip doesn't stay hot enough to burn off the carbon deposits, and so a build up occurs.
Switching to a colder or hotter plug will not increase horsepower, but could affect engine performance. Choosing a plug that is too hot can result in preignition or detonation. A plug that is too cold could cause an engine to stumble, misfire or foul.
These spark plugs are more efficient at transferring heat and reducing the likelihood of engine knocks or pre-detonation, which becomes a concern at higher boost and horsepower levels.
No, use OEM plugs only. The colder heat range means that it isn't going to burn fuel as well under normal driving conditions and this will actually hurt your fuel economy and throttle response.
An example of an NGK racing plug is R5671A-11. Here, R5671A represents the plug type and -11 represents the heat range. The stock number is 6596. NGK lists a design symbols chart in the front of every spark plug catalog. Decoding Chart.
So again, in the case of BPR6ES, the '6' indicates it is suitable for mid range heat. After the number, the next letter or letters identify the reach of the spark plug. The reach is distance between the point at which it runs out of thread at the metal shell and the ground electrode at the end of the spark plug.
Identified for letter R in the ceramic resistance. This spark plug incorporates of 3 to 7,5 k ohms (or in some cases of 1 to 2KΩ) ceramics resistance to attenuate the ignition noises generated during spark emission.
For a spark plug to function properly, it must have a tip temperature high enough to burn off carbon deposits (self-cleaning) and avoid fouling, while remaining low enough to avoid overheating the ceramic firing end and pre-ignition.