07-26-2011, 06:58 PM #1
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]  [E] [A] - .
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
Back to topField one: Thread Diameter and Wrench SizeThread 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
2 = "hot" to 14 = "cold" (HOT & COLD PLUGS)Part ThreadedTotal reach = 19.0mmThread = 12.7mmBM_A, B_LM types 9.5mm CMR_A types 9.5mm
Heat rating and heat flow path of NGK Spark PlugsHOT TYPE (BP 5 ES)
It has a larger surface exposed to the combustion gasses, it dissapates heat slowly, its firring end heats up quicklyCOLD TYPE (BP 7 ES)
It has a smaller surface exposed to the combustion gasses, it dissipates heat quickly, its firing end does not heat up quicklySo lower the number hotter the plugThe 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-850°C. If the tip temperature is lower than 500°C, 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 850°C 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 70°C to 100°C from the combustion chamber. A projected style spark plug firing tip temperature is increased by 10°C to 20°C.
Back to top
'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.
07-26-2011, 07:50 PM #2
07-26-2011, 09:39 PM #3
- Join Date
- Aug 2006
And don't confuse these with any other make of plugs. They are all different
Users Browsing this Thread
There are currently 1 users browsing this thread. (0 members and 1 guests)
By DrWeaseL in forum Yamaha PWC Performance (4-stroke)Replies: 4Last Post: 03-22-2011, 10:11 PM
By Cashito in forum 4-Tec PerformanceReplies: 1Last Post: 05-07-2010, 12:58 PM
By Rio Vista in forum Yamaha PWC Performance (2-stroke)Replies: 7Last Post: 09-30-2007, 07:52 AM
By BoostedH23a1 in forum 4-Tec PerformanceReplies: 1Last Post: 06-21-2007, 04:16 PM
By andy95'slx780 in forum Polaris PWC PerformanceReplies: 6Last Post: 10-17-2006, 02:07 AM