SC-Power Spark Plugs


NGK B8ECS	NGK B7ECS
£40.68 for 8 plugs including vat and delivery	£40.68 for 8 plugs including vat and delivery

Spark Plug information


Defects An intact spark plug shows a white-grey discolouring Normal appearance This is how an intact spark plug looks. The white/grey discolouration is harmless. It comes from fuel additives which leave residue when burned and the result is a controlled, normal combustion. Heavy deposits accumulate as a result of poor fuel quality and defective engines burn oil, for example Deposits Here you can see a spark plug with heavy deposits. This can be caused by poor fuel quality, high oil consumption from a mechanically-worn engine or burning of coolant from damaged cylinder head seals and can promote glow ignitions (the deposits glow after). Insulator breakage can lead to engine damage Insulator breakage An insulator break, as is visible in this image, can lead to engine damage. The cause of such insulator breakage is the use of the wrong torque or the spark plugs were dropped on a hard surface (e.g. workshop floor) before installation. If a spark plug overheats the middle and earth electrodes melt together Melting The middle and earth electrodes have melted together on this spark plug That happens if the spark plug overheats. In this case, it is also possible that the piston could melt. The cause could be the selection of the wrong spark plug (incorrect heat rating) or a malfunction of the engine (pulsatory combustion or glow ignition). Carbon deposits appear if the spark plug is frequently operated below its self cleaning temperature (450 °C) Carbon deposits Here you can see a spark plug clogged with carbon deposits. Carbon deposits appear if the spark plug is frequently operated below its self-cleaning temperature (450 °C) - for example, when only short distances are driven or an incorrect heat rating (too cold) was selected.

Firing end appearances
The appearance of the firing-end of a used spark plug graphically reflects the condition of an engine, the suitability of the spark plug heat range, and whether or not the fuelling and ignition systems are correctly set. Normal condition An engines condition can be judged by the spark plugs firing end appearance. 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 correctly. Deposits The accumulation of deposits on the firing end is influenced by oil leakage, fuel quality and the engines operating period. Deposits come from: Fuel: C (carbon), Pb (lead), Br (bromine) Lubricating oil: C, CA (calcium), S (sulphur), Ba (barium), Zn (zinc) Others: Fe (iron), Si (silicon), Al (aluminium), etc. Dry and wet fouling Although there are many different causes, if the insulation resistance between the center electrode and the shell is over 10M ohms, the engine can be started normally. If the insulation resistance drops to 0, the firing end is fouled by either wet or dry carbon. Lead fouling Lead fouling usually appears as yellowish brown deposits on the insulator nose and this cannot be detected by a resistance tester at room temperature. Lead compounds combine at different temperatures; those formed at 370 420 degrees Celsius having the greatest influence on the resistance. Overheating After having overheated, the insulator tip is glazed or glossy, and deposits which have accumulated on the insulator tip have melted. Sometimes these deposits have blistered on the insulators tip. Breakage Breakage is usually caused by 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 requires higher voltages. Worn spark plugs also reduce the engines efficiency, resulting in reduced fuel economy and increased exhaust emissions. The normal rate of gap growth is about 0.01 0.02mm/1,000 Km for four stroke engines and about 0.02 0.04mm/1,000 Km for two stroke engines. Erosion, Corrosion, Oxidation The material of the electrodes has oxidized, and when the oxidation is heavy it will be green on the surface. The surfaces of the electrodes are also fretted and rough. Abnormal erosion Abnormal electrode erosion is caused by the effects of corrosion, oxidation, reaction with lead, all resulting in abnormal gap growth. Lead erosion Lead erosion is caused by lead compounds in the gasoline which react chemically with the material of the electrodes ( nickel alloy) at high temperatures. Crystals of nickel alloy fall off because of the lead compounds permeating and separating the grain boundary of the nickel alloy. Typical lead erosion causes the surface of the ground electrode to become thinner, and the tip of the electrode looks as it it has been chipped. 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 degrees Celsius.

Pre-ignition range
Pre-ignition is a condition whereby combustion is initiated within the combustion chamber before the spark occurs at the plug. This results in uncontrolled ignition and combustion conditions. If a spark plug operates at a temperature in excess of 1000 degrees Celsius for a prolonged period the electrodes can start to overheat. When excessively overheated, pre-ignition can occur, the electrodes and insulator tip may melt and piston damage may result. Pre-ignition is usually caused by a temperature exceeding 850 degrees Celsius – 1000 degrees Celsius (1600 degrees Fahrenheit – 1800 degrees Fahrenheit) Causes of overheating Over-advanced ignition timing Too lean fuel mixture Excessive deposits accumulated in combustion chamber Insufficient cooling Insufficient spark plug tightening or failure to fit gasket Too low octane gasoline Too hot a spark plug fitted Overheated The plug has been subjected to a relatively heavy load and evidence of overheating can be seen in the oxidized electrodes and melted deposits which have formed on the insulator surface. Recommendation Check for over-advanced ignition timing and too lean fuel mixture. Check spark plug tightening and gasket. If conditions recur, use plug one step colder in heat range. Melted Overheated plug with melted electrodes and blistered ceramic insulator surface. Recommendation Check for over-advanced ignition timing and too lean fuel mixture. Check spark plug tightening and gasket. If conditions recur, use plug one step colder in heat range. Worn Spark Plug A worn spark plug not only wastes fuel but also loads the whole ignition system because the expanded gap requires higher voltage. As a result, a worn spark plug may also cause engine damage and increased exhaust emissions. Recommendation Spark plugs should be replaced. Deposits The accumulation of deposits on the firing end is influenced by oil leakage, fuel quality and engine operating period. Recommendation Check for excessive amounts of lubricating oil entering into the combustion chamber. High quality oil should be used. Spark plug tip temperature
Corona stain
A brown stain – often mistaken for gas leakage – is sometimes observed in a ring around where the insulator joins the metal shell of the spark plug. This discolouration is generally called Corona Stain and is the result of oil particles present in the air around the engine adhering to the insulator surface. The Corona Stain is often seen on spark plugs that are installed deep into the engine such as on many four valves per cylinder engine applications. This is because oil particles are not blown away by air circulating around the engine compartment and thus adhere to the insulator surface. It is important to understand that Corona Stain causes no deterioration to the function of the spark plug.