Guide pour Bougie d'Allumage

L'Essentiel pour Bougie d'Allumage - Que Signifient Les Symboles Sur Une Bougie d'Allumage NGK
Types de Bougie d'Allumage Bougies d'Allumage Chaudes & Froides
Problèmes de Bougie D'Allumage -(Comment Lire Une Bougie d'Allumage) Encrassement & Pré-Allumage
Comment Installer - Outils pour Bougie d'Allumage
L'ESSENTIEL POUR BOUGIE D'ALLUMAGE:
La Bougie d'Allumage a deux fonctions primaires:
* Allume le mélange air/carburant* Transfert la chaleur à partir de la chambre de combustion
Les Bougies d'Allumage porte une énergie électrique et transforme le carburant en énergie. Un montant suffisant de voltage doit être fourni par le système d'Allumage pour allumer à travers l'espace inter-électrodes de la bougie d'allumage. Cela
s'appelle "Performance Electrique."La température de la bougie d'allumage's firing end doit être garde assez bas pour éviter le pré-allumage, mais assez élevé pour éviter l'encrassement. Cela s'appelle "Performance Thermique", et est déterminée par la gamme de chaleur sélectionnée. C'est important de se souvenir que les bougies d'allumage ne crées pas de chaleur, elles retirent la chaleur seulement. La bougie d'allumage fonctionne comme un échangeur de chaleur
en tirant l'énergie thermique non désirée hors de la chambre de combustion, et en transferrant la chaleur au système de refroidissement du moteur. La gamme de chaleur est définie comme la capacité de la bougie à dissiper la chaleur.

Le transfert de taux de chaleur est déterminé par:
* La longeur de l'embout de l'isolateur
* Le Volume du gaz autour de l'embout de l'isolateur
* Les matériaux/ la construction de l'électrode centrale et l'isolateur en porcelaine
La gamme de chaleur d'une bougie d'allumage n'a pas de relation avec l'actuel voltage transferré à travers la bougie d'allumage. Plutôt, la gamme de chaleur est une mesure de la capacité de la bougie d'allumage à retirer la chaleur de la chambre de combustion. La mesure de la gamme de chaleur est déterminée par plusieurs facteurs; la longeur de l'embout de l'isolateur central en céramique et sa capacité à absorber et transférer la chaleur de combustion, la composition du matériau de l'isolateur et le matériau de l'électrode centrale.

La longeur de l'embout de l'isolateur est la distance a partir de 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.


What Do The Symbols On A NGK Spark Plug Mean

DPR9EA-9

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 1 D gives you the size of the thread, pitch and hex can be one to two letters
Field 2 PR 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

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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

COLD 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 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-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.

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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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Spark Plug Problems

How To Read a Spark Plug
Normal Condition
An engine's condition can be judged by the appearance of the spark plug's firing end. 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.

Dry and Wet Fouling
Although there are many different cases, if the insulation resistance between the center electrode and the shell is over 10 ohms, the engine can be started normally. If the insulation resistance drops to 0 ohms, the firing end is fouled by either wet or dry carbon.
Overheating
When a spark plug overheats, deposits that have accumulated on the insulator tip melt and give the insulator tip a glazed or glossy appearance.
Deposits
The accumulation of deposits on the firing end is influenced by oil leakage, fuel quality and the engine's operating duration.
Breakage
Breakage is usually caused by thermal expansion and thermal shock due to sudden heating or cooling.

Normal Life
A worn spark plug not only wastes fuel but also strains the whole ignition system because the expanded gap (due to erosion) requires higher voltages. Normal rates of gap growth are as follows:
Four Stroke Engines: 0.01~0.02 mm/1,000 km (0.00063~0.000126 inches/1,000 miles)
Two Stroke Engines: 0.02~0.04 mm/1,000 km (0.000126~0.00252 inches/1,000 miles)

Abnormal Erosion
Abnormal electrode erosion is caused by the effects of corrosion, oxidation and reaction with lead - all resulting in abnormal gap growth.
Melting
Melting is caused by overheating. Mostly, the electrode surface is rather lustrous and uneven. The melting point of nickel alloy is 1,200~1,300°C (2,200~2,400°F).
Erosion, Corrosion and Oxidation
The material of the electrodes has oxidized, and when the oxidation is heavy it will be green on the surface. The surface of the electrodes are also fretted and rough.
Fouling & Pre-ignition
The firing end appearance also depends on the spark plugs tip temperature. There are three basic diagnostic criteria for spark plugs: good, fouled and overheated. The borderline between the fouling and optimum operating regions (500&defC) is called the spark plug self-cleaning temperature. The temperature at this point is where the accumulated carbon and combustion deposits are burned off.

Keep in mind the insulator nose length is a determining factor in the heat range of a spark plug, the longer the insulator nose, the less heat is absorbed, and the further the heat must travel into the cylinder head water jackets. This means the plug has a higher internal temperature, and is said to be a hot plug. A hot spark plug maintains a higher internal operating temperature to burn off oil and carbon deposits, and has no relationship to spark quality or intensity.

Conversely, a cold spark plug has a shorter insulator nose and absorbs more combustion chamber heat. This heat travels a shorter distance, and allows the plug to operate at a lower internal temperature. A colder heat range is necessary when the engine is modified for performance, subjected to heavy loads, or is run at a high rpm for a significant period of time. Colder spark plugs remove heat quicker, reducing the chance of pre-ignition/detonation. Failure to use a cooler heat range in a modified application can lead to spark plug failure and severe engine damage.

Fouling

* Will occur when spark plug tip temperature is insufficient to burn off carbon, fuel, oil or other deposits
* Will cause spark to leach to metal shell...no spark across plug gap will cause a misfire
* Wet-fouled spark plugs must be changed...spark plugs will not fire
* Dry-fouled spark plugs can sometimes be cleaned by bringing engine up to operating temperature
* Before changing fouled spark plugs, be sure to eliminate root
cause of fouling

Pre-ignition

* Defined as: ignition of the air/fuel mixture before the pre-set ignition timing mark
* Caused by hot spots in the combustion chamber...can be caused (or amplified) by over advanced timing, too hot a spark plug, low octane fuel, lean air/fuel mixture, too high compression, or insufficient engine cooling
* A change to a higher octane fuel, a colder plug, richer fuel mixture, or lower compression may be in order
* You may also need to retard ignition timing, and check vehicle's cooling system
* Pre-ignition usually leads to detonation; pre-ignition an detonation are two separate events

Replacing Plugs
Start by using either a bicycle tire pump or an air compressor and pump a few bursts of air to rid the spark plug area of dirt, dust or gravel. Alternatively, clean off the old plug and the area around it with a rag or small paint brush. These steps help prevent any foreign material from falling down into the cylinder when the old plug is removed.

OK, time to set the gap of the new plug with a spark plug gap gauge (Remember the proper gap is specified in your manual). With your feeler gauge slide the correct thickness wire or feeler between the inner and outer electrodes at the tip of the plug. The feeler will slide between the electrodes with a slight drag when the plugs are properly gapped. If the gap isn't right, slightly bend the outer electrode until you achieve the right gap. Ensure the outer electrode is inline over the inner electrode.
Next, have a look at the cylinder head threads. Are they in good condition, clean, and free of dirt? New spark plug should freely screw into the cylinder head by hand. Any binding of the plug is an indication of debris or damage in the thread. TIP: lube the plug threads with a little grease or spray lubricant before you install them, this will make for an easier removal at your next spark plug change.

Put the plug-wire end of the new plug in the socket and, holding just the extension, push it all the way in. Now carefully guide the spark plug into the hole. Try not to ram it in or bang it on anything because this can alter the gap or even worse damage the thread on the plug. With it sitting in the hole, begin to screw the new plug in by hand slowly. Starting them off by hand instead of using the wrench will keep you from accidentally cross-threading one of the plugs. Screw it in by hand until it stops, then put the wrench on the end and tighten it snugly. If you have a torque wrench, you can torque it to spec, but if you don't, just make it tight without overdoing it. The metal in there is soft and can be damaged by over tightening. If you are pulling hard enough to make a sound come out of your mouth, like a grunt, you're overdoing it
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Spark plug Tools
Spark Plug Spanner
feeler gauge
lube

If things go wrong.
Spark Plug Engine Head Threadsaver ( 12mm and 14mm)

Threadsaver For 12mm Spark Plugs: The Thread Saver does what it's name implies... it saves threads. This unique tool was designed for one purpose and that is to clean or repair damaged spark plug port hole threads.
The ThreadSaver comes in two sizes, for the most popular range of spark plugs, 12mm and 14mm and is suitable for plain or tapered plug seat types. All the you need to use it is a 5/8" spark plug socket or spanner. ThreadSaver will save you time and money.

The ThreadSaver is a collapsible tap with a centre rod that enables the user to regulate the amount of pressure at the thread cutting end of the tool. It enables the user to adjust the cutting depth of the thread by simply pushing the rod toward the cutting head to increase depth or retracting the rod to reduce cutting depth.
To start the operation, the expanding rod is removed. This allows the collapsible tap end to be inserted into the spark plug port hole. Bearing in mind this unique tool cleans or cuts the thread on the way out. With the collapsible tap end, the tool is inserted past the damaged or contaminated spark plug thread. The expanding rod is replaced through the centre of the ThreadSaver tool and now comes the best part, the ThreadSaver is wound out cleaning or repairing and realigning the thread and with the help of a little grease on the tap end, metal and carbon particles are brought out through the spark plug port hole along with the ThreadSaver tool.
The ThreadSaver is a cheap investment, is simple, and is fast and easy to use. It will go a long way in assisting to reduce lost labor time on a fairly common workshop problem when replacing spark plugs.
A tool that every technician should have, ThreadSaver works on cast iron and alloy cylinder heads, can be used on cars, trucks, motor cycles, marine, lawn mowers, chainsaws or anything that uses a 12mm or 14 mm spark plug. Back to top