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  1. #1
    bowsniper's Avatar
    Join Date
    Aug 2008

    What Do The Symbols On A NGK Spark Plug Mean

    NGK spark plug codes generally consist of six fields, which break down as follows:
    [D] [P R] [9] [E] [A] - [9].
    Some fields (e.g., the second field) are optional, and some fields may have multiple letters.
    Field 1D gives you the size of the thread, pitch and hex can be one to two letters
    Field 2PR these two give you the contruction shape or feature in this case
    it would be projected centre electrode insulator/ resister type
    Field 3.9 this number shows you the heat rating
    Field 4.E gives you the thread reach
    Field 5. A shows you what type of firing end contrustion
    Field 6. 9 the last one gives the spark gap not all plugs show this
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    Field one: Thread Diameter and Wrench Size
    Thread dia Pitch Hex A 18mm 1.50mm 25.4mm B 14mm 1.25mm 20.8mm C 10mm 1.00mm 16.0mm D 12nn 1.25mm 18.0mm E 8mm 1.00mm 13.0mm G PF 1/2" pipe 23.8mm AB 18mm 1.50mm 20.8mm BC 14mm 1.25mm 16.0mm BK 14mm 1.25mm 16.0mm DC 12MM 1.25mm 16.0mm BM_A 14mm 1.25mmm 19.0mm BPM_A 14mm 1.25mm 19.0mm CM_6 10mm 1.00mm 14.0mm Field Two: Plug Contruction Shape or Feature Contruction Shape or Feature M compact type (hex. 19mm) L short type P projected insulator type R resistor type U surface or semi-surface discharge Z inductive suppressor Letters may be combined Field three: Heat Rating
    2 = "hot" to 14 = "cold" (HOT & COLD PLUGS) Field four: Thread Reach Thread Reach E 19.0mm H 12.7mm L 11.2mm EH
    Part Threaded
    Total reach = 19.0mm
    Thread = 12.7mm
    BM_A, B_LM types 9.5mm CMR_A types 9.5mm Field Five: Firing and Construction Firing and Construction C short ground electrode F tapered seat G fine-wire center electrode, nickel J 2 ground electrodes (special shape) K 2 ground electrodes for certain Toyota -L half heat range -LM insulator length = 14.5mm M insulator length = 18.5mm -N special ground electrode P platinum tip Q 4 ground electrodes R delta ground electrod S super copper core T 3 ground electrodes V fine-wire centre electrode, gold palladium VX platinum center electrode W tungsten electrode X booster gap Y v-grooved center electrode with extra projection Field Six: Spark Gap Spark Gap (pre-set) 8 0.8mm 0.032" 9 0.9mm 0.036" 10 1.0mm 0.040" 11 1.1mm 0.044" 13 1.3mm 0.050" 14 1.4mm 0.055" 15 1.5mm 0.060" 20 2.0mm 0.080" None Std. gap HOT & COLD PLUGS
    Heat rating and heat flow path of NGK Spark Plugs
    HOT TYPE (BP 5 ES)
    It has a larger surface exposed to the combustion gasses, it dissapates heat slowly, its firring end heats up quickly
    It has a smaller surface exposed to the combustion gasses, it dissipates heat quickly, its firing end does not heat up quickly
    So lower the number hotter the plug
    The insulator nose length is the distance from the firing tip of the insulator to the point where insulator meets the metal shell. Since the insulator tip is the hottest part of the spark plug, the tip temperature is a primary factor in pre-ignition and fouling. Whether the spark plugs are fitted in a lawnmower, boat, or a race car, the spark plug tip temperature must remain between 500C-850C. If the tip temperature is lower than 500C, the insulator area surrounding the center electrode will not be hot enough to burn off carbon and combustion chamber deposits. These accumulated deposits can result in spark plug fouling leading to misfire. If the tip temperature is higher than 850C the spark plug will overheat which may cause the ceramic around the center electrode to blister and the electrodes to melt. This may lead to pre-ignition/detonation and expensive engine damage. In identical spark plug types, the difference from one heat range to the next is the ability to remove approximately 70C to 100C from the combustion chamber. A projected style spark plug firing tip temperature is increased by 10C to 20C.

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    Plug Types
    'S' Type (e.g BP6ES)
    These are standard plugs with copper cored centre electrodes. A copper core offers superior heat conductivity hence heat is removed from the firing end of the plug and 'hot spots' are prevented - these can lead to pre-ignition. A copper core also allows a longer insulator nose to be used - this protects against fouling.
    'G' Type (e.g. B10EG)
    These feature a smaller diameter centre electrode tip made of nickel alloy. The smaller diameter means a lower voltage is required to produce a spark. As the tip is made of conventional Nickel Alloy the service life is reduced. Best suited to applications where plugs are changed regularly.
    'V' Type (e.g. B10EV)
    The centre electrode is made of gold palladium alloy and is only 1.0mm in diameter. This means an even lower voltage requirement than 'G' types.
    'GV' Types (e.g. B9EGV)
    These plugs have a centre electrode made of precious metal similar to 'V' types. The insulator nose is of improved design, allowing better gas flow around the firing end. The ground electrode is shorter and stronger making the 'GV' range ideal for most severe racing applications.
    'VX' Type (e.g. B8EVX)
    These have an even smaller centre electrode than 'V'/'GV' types at 0.8mm. The centre electrode is made of platinum. The ground electrode is taper cut. These features mean an even lower voltage is needed than that for 'V' types. The result is better ignitability, improved starting, idle stability and anti-fouling performance
    'IX' Type (e.g. BR8EIX)
    Similar in design to the 'VX' type but using the precious metal iridium for the centre electrode. The properties of iridium allow the centre electrode to be even smaller than 'VX' types at 0.6mm - without compromising durability. Electrical energy is highly concentrated due to the extremely small tip diameter with the result of best performance in terms of starting, idling and throttle response.

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  3. #3

    Join Date
    Aug 2006
    And don't confuse these with any other make of plugs. They are all different

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