8/14/2019 How to Choose a Plug
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Spark plug heat dispersal
What is a spark plugs heat range ?
How to Choose a Plug
Various circumstances such as engine conditions and driving
conditions are rough measures for choosing a plug. For example, if
strenuous driving is continued for a long time using normal plugs, the
plug will overheat. This is why the idea of a regular plug for a regular
car doesnt work. Whats important is to inspect the condition of your
current plugs, and then choose a plug accordingly.
The degree to which a spark plug disperses the heat it
receives is called its "heat range". Spark plugs with a
high degree of heat dispersal are called high heat range
(cold type) and those with a low degree of heat dispersal
are called low heat range (hot type).
This is largely
determined by the
temperature of the
gas inside the
combustion
chamber and the
spark plug design.
The heat range will changewith the seasons.
When the air temperature is high, as in the summer,
the inlet air temperature becomes higher, increasing
the load on the engine. In times like this, it's better to
choose a plug with a higher heat range.
The more horsepower is increased,the higher the required heat range.
If the horsepower has been increased through tuning,
the increase in explosive power leads to an increase
in combustion chamber temperature, making pre-ignition more likely; in such cases it is necessary to
choose a plug with a higher heat range and a higher
level of heat resistance.
Glossary of spark plug terms
Low heat range and high heat rangeLow heat range plugs have long insulator leg sections and the surfacearea affected by the flame and the gas pocket capacity are large.Also, since the heat release path from the insulator leg section to the
housing is long, heat dispersal is low and the temperature of thecenter electrode rises easily.On the other hand, high heat range plugs have short insulator legsand the surface area affected by the flame and the gas pocketcapacity are small.Also since the heat release path from the insulator leg section to thehousing is short, heat dispersal is high and the temperature of thecenter electrode does not rise easily.
The relationship between the spark plugtemperature and vehicle speed and heat rangeThere are restrictions on the temperatures at which spark plugscan be used: the lower limit is the self-cleaning temperature andthe upper limit is the pre-ignition temperature.A spark plug onlyfunctions completely when its center electrode temperature isbetween these temperatures of about 500C and 950C.
Water1
Cooled by intakeair-tuel mixture
2
Low heatrange(hot type)
spark plugs
High heatrange(cold type)spark plugs
Gas pocket
Self-cleaning temperature1 Pre-ignition temperature2
Low heat range (hot type) spark plugs3 Standard spark plugs4
High heat range (cold type) spark plugs
S: Vehicle speed T: Spark plug temperature (C)
5
HeatRange
31
27
24
22
20
To prevent plug overheat
Standard Plugs
Level of TuningLow High
To prevent carbon fouling/ oil fouling
Application
16 20 22 24 2714
03
http://www.globaldenso.com/PLUG/
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