"Cold" spark plugs feature a relatively short insulator tip and they remove heat from the combustion area quite fast, in order to avoid advanced ignitions. They have a longer insulator tip and they achieve a temperature higher than the deposition zone relatively fast. "Hot" spark plugs remove heat from the combustion area relatively slowly. The range of thermal values for BRISK spark plugs extend from the warmest to the coldest, namely 19, 18, 17, 15, 14, 12, 10 and 08. In order to achieve the correct temperature of the insulator tip for a given engine, the spark plugs are produced in various thermal values. High temperature results in pre-ignitions of the air-fuel mixture and further compression of the mixture already ignited leads to high temperature, which can cause serious damage to the engine. Too high temperature of the insulator tip is undesirable. The spark plug operates in an optimum manner. Providing a higher temperature of the insulator tip, no further combustion deposits are formed, but those already existing will not be burnt until the insulator tip temperature rises above 475 ☌ - the so-called self-cleaning zone. In this temperature range, no new deposits are formed and those existing will be burnt. A consequence of these combustion deposits on the insulator tip is reduction in electrical insulation resistance accompanied by failing ignitions and after a certain period of time even by a failure of the spark plug performance. If the insulator tip temperature drops into the so-called deposit zone, combustion deposits (carbon, non-combusted fuel, lubrication oil, impurities from the atmosphere) start to form on the insulator tip surface. One heat range changes the spark plug insulator tip temperature by about 75 - 100 degree Celsius.Ī. In order to ensure sufficient insulation between center and ground electrodes it is necessary, to keep the insulator tip (the part of the insulator projecting into the engine area) within an optimum temperature range. Insulator tip temperature is influenced by the proper choice of spark plug heat range. Two basic conditions for proper performance of a spark plug are given by sufficient electrical insulation between the center and ground electrodes, and heat transfer from the parts of the spark plug projected into the combustion chamber. Adapt to specific engine characteristics and widely varying driving/load conditions.Run hot enough to burn off combustion deposits that would otherwise collect on the sparkplug insulator tip and cause fouling, that leads to misfire.Stay cool enough to avoid pre-ignition and/or electrode destruction due to detonation.It must do this in a precise and controlled manner so the spark plug will:
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Spark plug heat range is the measure of how fast the spark plug tip dissipates combustion heat. Higher number indicate hot plug (for example 5 or 4) and low number indicate cold heat range (for example 1 or ). If the insulation resistance drops to 0, the firing end is fouled by either wet or dry carbon.Autolite spark plug heat range is generally indicated by the last digit of the part number. Others: Fe(iron), Si(silicon), Al(Aluminum)īreakage is usually caused by thermal expansion and thermal shock due to sudden heating or cooling of the spark plug.Īlthough there are many different cases, if the insulation resistance between the center electrode and the shell is over 10M, the engine can be started normally in all cases. Lubricating oil: C, CA(calcium), S(sulphur), Ba(barium), Zn(zinc) The accumulation of deposits on the firing end is influenced by oil leakage, fuel quality and the engine's operating period. Sometimes these deposits have blistered on the insulator's tip. When having been overheated, the insulator tip on the spark plug is glazed or glossy, and deposits which have accumulated on the insulator tip have melted. If the firing end of a spark plug is brown or light gray, the condition can be judged to be good and the spark plug is functioning optimally. The converter can also be used to convert regular spark plug to iridium spark plug.Īn engine's condition can be judged by the spark plugs firing end's appearance. Select the manufacturer of your current spark plug, then enter the number of the plug below.įor ngk, bosch, champion, motorcraft and densospark plugs there are 2 numbers, P/N and STK, try your number on both. Converts between NGK, Autolite, Champion, Denso, Bosch and Accel spark plugs! is a web service that lets you find replacement spark plugs for your car, motorcycle, marine vehicle and lawnmover. NGK P/N"NGK STK"Accel"AC Delco"Autolite"Beck Arnley"Blue Crown"Bosch P/N"Bosch STK"Champion P/N"Champion STK"Denso P/N"Denso STK"Denso Iridium P"Denso Iridium S"GM OEM NR"Lodge"Mighty"Mopar"Motorcraft P/N"Motorcraft STK"Napa"Prestolite"Splitfire"Stitt"Valley Forge"NGK TYPE"Thread size"Hex size"Reach"Seat type"Projected tip"