Description * Spark plugs may need to be gapped to fit your application. Check your manual for a proper gap size. * NGK Iridium IX Spark Plugs
Designed specifically for the performance enthusiast. Iridium IX offers extreme ignitability, improved throttle response and superior anti fouling
Are special plugs always necessary on a modified engine?
- Fine Iridium tip ensures high durability and a consistently stable spark
- Iridium alloy has extremely high melting point, perfect for today's high-tech, high-performance engines
- ''Trivalent Metal Plating'' has superior anti-corrosion and anti-seizing properties
- Outstanding acceleration, high fuel efficiency and durability
- Ultimate design, technology and performance
Modifications that will typically not require specialized plugs (in most cases the factory installed plug will be more than adequate) include adding a free-flowing air filter, headers, mufflers and rear-end gears. Basically, any modification that does not alter the overall compression ratio will not usually necessitate changing plug types or heat ranges. Such minor modifications will not significantly increase the amount of heat in the combustion chamber, hence, a plug change is probably not warranted.
However, when compression is raised, along with the added power comes added heat. Since spark plugs must remove heat and a modified engine makes more heat, the spark plug must remove more heat. A colder heat range spark plug must be selected and plug gaps should be adjusted smaller to ensure proper ignitability in this denser air/fuel mixture. Typically, for every 75-100 hp you add, you should go one step colder on the spark plug's heat range. A hotter heat range is not usually recommended except when severe oil or fuel fouling is occurring.
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NGK Iridium IX Spark Plugs
.044 Gap; 14mm, 3/4in Reach, 5/8in Hex; Resistor; ISO 5
Subaru (incl. Impreza, Forester)
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