HKS SUPER FIRE RACING M40G HKS HKS50003-M40G
HKS SUPER FIRE RACING M40G HKS HKS50003-M40G
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HKS SUPER FIRE RACING M40G

HKS
HKS50003-M40G
4957266720301
Spark Plugs
11 Units In Stock - Ships Next Business Day
$ 270.00
FREE Ground Shipping!
$ 270.00

SKU: 50003-M40G | UPC: 4957266720301

HKS Super Fire Racing M40G Spark Plug 2002-2021 Subaru Impreza WRX STI Forester Legacy

HKS Super Fire Racing M40G delivers high-performance ignition for turbocharged Subaru EJ20 EJ25 engines. It fits 2002-2021 Impreza WRX STI Forester XT Legacy GT Outback XT models. Stronger spark improves combustion efficiency throttle response and power under high boost RPM.

Key Features

  • Fine wire center electrode: Promotes stable ignition kernel growth for complete fuel burn and consistent power delivery
  • Racing heat range 40: Resists fouling and handles extreme cylinder temperatures in boosted applications
  • Nickel alloy construction: Provides extended service life in competition environments with repeated heat cycles
  • Large ground electrode design: Shields flame kernel to prevent pre-ignition damage while maintaining spark focus
  • Pre-gapped specification: Ensures drop-in compatibility with OEM specs for Subaru EJ20 EJ25 turbo engines

Product Notes

  • Sold as single plug order quantity needed for full set replacement
  • Use anti-seize on threads during installation to prevent galling
  • Ships in protective foam insert box dimensions 3.5 x 1 x 1 inches

Installation Notes

  • Professional installation recommended.
  • Torque to 18-22 ft-lbs using thin wall socket to avoid cracking porcelain
  • Compatible with OEM coil packs and wiring no adapters required

This Part Fits

Year Make Model Submodel
2002-2007 Subaru Impreza WRX
2004-2007 Subaru Impreza WRX STI
2004-2013 Subaru Forester XT
2005-2009 Subaru Legacy 2.5 GT
2005-2009 Subaru Outback XT
2008-2014 Subaru Impreza WRX STI
2015-2021 Subaru WRX STI All

Why Choose HKS?

  • HKS pioneered JDM tuning since 1973 with motorsport-proven components
  • Plugs tested in endurance racing for reliability under extreme conditions
  • Precision-machined in Japan for exact OEM thread fit and gap accuracy

Frequently Asked Questions

  • Q: Does this fit 2004-2007 Subaru STI EJ25 turbo?
    A: Yes direct replacement for OEM plugs in all EJ25 turbo Impreza STI models from 2004-2007
  • Q: What material is the electrode made from?
    A: Racing-grade nickel alloy center wire and ground strap for heat resistance and anti-fouling properties
  • Q: What is the warranty and gap spec?
    A: 1-year manufacturer warranty pre-gapped to 0.8-0.9mm verify with gap tool before final torque

Shipping & Handling

  • Method: UPS Ground or USPS Priority
  • Availability: In stock - ships same or next business day
  • Packaging: Compact cardboard box with foam insert 3.5 x 1 x 1 inches
  • Weight: 0.1 lb

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