The plugs used by winning racers.
These NGK Iridium IX spark plugs feature an ultra fine center electrode that’s designed not too thin to ensure maximum durability and life of the spark plug and not too thick for an accurate and consistent spark. They represent the ultimate evolution of spark plug technology and performance. Iridium is significantly stronger than any metal used in spark plugs today. It’s the hardest metal used (in fact, iridium is 6 times harder than platinum) which has allowed NGK engineers to design an ultra fine center electrode reducing the voltage requirement for spark.
MWR recommends NGK’s 9 heat range plugs in extreme turbocharged, supercharged or nitrous fed 4-cylinders. They are also good for ultra high heat applications such as road racing. They have excellent durability and performance. Heat range 9 is extremely cold meaning they are very prone to fouling out on cold starts or if run too rich. These plugs intended for racing use only, do not work well for street.
Price is for one spark plug.