HKS Super Fire Racing M40i Spark Plug (1pc) – Iridium Performance Plug | High Heat Range Racing Plug

HKS SUPER FIRE RACING M40i - Single Qty Plug

The HKS Super Fire Racing M40i spark plug is engineered for extreme performance environments where standard plugs fail. Designed specifically for high-boost, high-compression, and racing applications, the M40i offers superior ignition stability under elevated cylinder pressures and temperatures.

As part of the HKS Super Fire Racing series, the M40i features a fine iridium center electrode that improves ignition efficiency while maintaining durability under aggressive driving conditions. This allows for consistent spark delivery even in engines running high boost levels or advanced tuning setups.

The “40” in M40i represents a colder heat range, making it suitable for modified engines that generate increased combustion temperatures. Using the correct heat range is critical to preventing pre-ignition and maintaining optimal engine performance.

Ideal for turbocharged builds, track cars, and high-performance street applications, the HKS M40i is a proven upgrade for enthusiasts pushing their engines beyond factory limits.

Features 

0.6mm Iridium 

Alloy Center Electrode Iridium alloy center electrode reduces voltage requirement and improves ignition performance and durability. 

Outer Electrode with Platinum Chip The outer electrode incorporates a square platinum chip which improves durability, and combining with the iridium center electrode boosts ignition performance. The outer electrode features a shortened tip design and tapered shape while maintaining the necessary space for proper ignition. 

Short Type Outer Electrode (Anti-Vibration) The outer electrode has been shortened and engineered with the ideal shape to decrease weight for resistance against vibration. This anti-vibration design improves longevity of the outer electrode. 

Thermal Edge After long idling or under various combustion conditions, carbon buildup can occur causing misfires. The thermal edge of the ceramic insulator discharges to help decrease carbon deposits. 

Spark Support Gap Discharge occurs in the spark support gap (space between the tip of insulator and the base of the outer electrode) to help prevent carbon buildup.