NGK 97537 R2558E-9 Racing Iridium Plug 12mm Gasket Heat Range 9 Subaru BRZ Scion

Vehicle Fitment

• 2013-2025 Subaru BRZ (2.0L FA20 and 2.4L FA24, All Trims)
• 2013-2016 Scion FR-S (2.0L FA20, All Trims)
• 2017-2025 Toyota 86, GT86, and GR86 (2.0L FA20 and 2.4L FA24, All Trims)
• Additional applications using a 12mm x 1.25mm gasket seat plug with 26.5mm reach and 9/16" hex - verify with engine specifications

Fitment Notes

• Thread: 12mm x 1.25mm gasket seat - confirm head thread spec before ordering
• Hex Size: 9/16" (14mm) - note this is smaller than the standard 5/8" hex used by many other 12mm plugs; use a 14mm spark plug socket
• Reach: 26.5mm (1.04") - verify cylinder head depth for your application
• Pre-set gap: 0.028" (0.7mm) - adjust gap to match engine tune, boost level, and ignition system requirements
• Heat Range 9 - a colder plug suited for modified, tuned, or forced-induction FA-series engines; verify correct heat range for your specific tune and power level
• Designed for racing and motorsport use - not covered under NGK's standard warranty
• Sold individually - 4 plugs required for FA20/FA24 4-cylinder applications

Features

• Fine-wire 1.0mm iridium center electrode delivers superior ignitability and dramatically reduces required firing voltage versus standard or copper plugs in high-compression and tuned FA-series applications
• Recessed electrode projection positions the iridium tip deeper in the insulator nose - ideal for high-compression and forced-induction racing engines where a standard or projected tip would be at risk of pre-ignition
• Platinum-tipped slant ground electrode minimizes quenching of the spark and provides excellent wear resistance under sustained high-RPM racing conditions
• Special insulator nose configuration engineered to improve throttle response and reduce fouling risk in hard-driven racing applications
• Pure alumina silicate ceramic insulator provides superior dielectric strength and efficient heat transfer from the firing tip to the shell
• Corrugated ribs on the insulator prevent electrical flashover in high-voltage or aftermarket ignition systems common in race builds
• Copper core maximizes heat dissipation and conductivity, keeping the electrode within its safe operating temperature range under extreme engine loads
• Triple gasket sealing eliminates combustion gas leakage for consistent compression retention at high cylinder pressures
• Trivalent metal plating (silver-chromate and zinc) resists corrosion and thread seizing during extended service intervals

Specifications

• NGK Stock Number: 97537
• NGK Part Number: R2558E-9
• Series: NGK Racing
• Heat Range: 9 (Colder)
• Thread Diameter: 12mm
• Thread Pitch: 1.25mm
• Seat Type: Gasket
• Reach: 26.5mm (1.04")
• Hex Size: 9/16" (14mm)
• Terminal Type: Solid (Non-Removable)
• Resistor: Yes - 5k Ohm
• Pre-Set Gap: 0.028" (0.7mm) - adjust for application
• Center Electrode: Iridium Fine Wire, 1.0mm, Recessed, Copper Core
• Ground Electrode: Platinum, Slant Type
• Insulator: Pure Alumina Silicate Ceramic with Corrugated Ribs
• Seals: Triple Gasket
• Torque (Cast Iron Head): 10.8-18 lb-ft
• Torque (Aluminum Head): 10.8-14.5 lb-ft
• Use: Racing / Motorsport
• Sold As: Individually (1 plug per package)

Included Components

• 1x NGK Racing Spark Plug (PN: R2558E-9 / Stock: 97537)

Product Description

The NGK 97537 (R2558E-9) is a Race Series spark plug with a fine-wire 1.0mm iridium center electrode and a platinum slant ground electrode, engineered specifically for the FA20 and FA24 boxer engines found in the 2013-2025 Subaru BRZ, 2013-2016 Scion FR-S, and 2017-2025 Toyota 86/GR86 platform. At Heat Range 9, this is a colder-running plug designed for modified, tuned, and forced-induction builds where the standard OEM heat range plug would risk pre-ignition or detonation under elevated cylinder temperatures. The recessed electrode projection keeps the iridium tip safely set back in the insulator nose, making it suitable for high-compression applications where a projected tip would be exposed to damaging combustion conditions.

The plug uses a 9/16" (14mm) hex - one size smaller than many 12mm plugs - so a 14mm spark plug socket is required for installation. Pre-gapped at 0.028" (0.7mm) from the factory, the gap should be verified and adjusted based on the specific tune, boost level, and ignition system. Triple gasket sealing and corrugated insulator ribs ensure gas retention and flashover protection at high cylinder pressures. As a racing plug, this unit is not covered under NGK's standard warranty. Sold individually - 4 plugs needed for FA-series 4-cylinder applications.