HKS SUPER FIRE RACING SPARK PLUG M40i | Heat Range 8 (50003-M40I)

Regular price $23.97 USD Sale price $23.97 USD Regular price $23.97 USD
In Stock!
SKU: hks50003-M40I
Product Description

HKS Super Fire Racing spark plugs are manufactured from NGK using their top tier "Iridium + Platinum Double Performance" to provide reliable ignition performance that produces faster and more efficient combustion. This also provides accurate ignition that ensures reliable engine performance for a long time and in various environments. 

This is recommended for drivers who track their vehicle often (naturally aspirated producing 250+ whp) or for those who daily drive a forced induction setup over 250 whp.


Tested Applications:

  • Honda CR-Z [ZF1/ZF2] (2011, 2012, 2013, 2014, 2015, 2016) 2 steps colder


  • 0.6mm Iridium Alloy Center Electrode: reduces voltage requirement and improves ignition performance and durability
  • Outer Electrode with Platinum Chip: improves durability thanks to a shortened tip design and tapered shape 
  • Short Type Outer Electrode (Anti-Vibration): engineered with the ideal shape to decrease weight for resistance against vibrations which in term improves longevity of the outer electrode.
  • Thermal Edge: helps decrease carbon deposits that occur after long idling or under various combustion conditions
  • 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


  • Type: Spark Plug
  • Plug Type: ISO
  • Manufacturer: NGK
  • Technology: Iridium + Double Platinum
  • Thread Size: 14mm Diameter - 19mm Length
  • Wrench Size: 16mm
  • Heat Range: NGK 8

To provide faster delivery and turn around time; Kami Speed ships products out from different warehouses throughout the United States. Usually averaging 1-4 business days for processing prior to shipping.

Depending on the package, we ship using different carriers according to the item's location, content, and size.

Freight truck & international items, will require up to 7 business days to ship due to size and logistics.

All orders made after 3:00pm ET will be shipped or processed the next business day.

Unless otherwise noted as "In Stock" or exact ETA. Special Order items have an ETA of 5+ weeks.

Orders over $500 will ship insured and over $1,000 with signature and insurance in order to guarantee delivery. Orders over $1000 may not be able to ship to a different address not listed as the billing address or confirm payment address from the form of payment used. Orders with suite numbers, different billing, or apartment numbers will require signature if valued over $100.

All international orders outside of the USA are subject to duties and taxes fees per your countries jurisdiction and determined by customs.
Kami Speed serves the right to ship using an alternative method if we see it fit, in order to expedite shipping and reduce your rate depending on product value.

Processing and logistics on in stock international orders can take up to 7 business days to process & ship.

In stock, non special order items can be returned within 30 days of the product arriving to your house or place of work.
Returns will NOT be accepted on Clearance Items, Final Sales, Special Orders, Opened, Installed, Incomplete, or Otherwise Used Products. In order to initiate a return, an RMA number must be requested and approved via e-mail. All returns will be subject to a 20% restocking fee minus complete shipping cost (roundtrip).

Any processed orders that have not shipped will incur a 6% cancelation refund fee unless the product was not available to ship within a timely manner. No fee will be incurred if used as store credit.

For complete details on our return policy, please see our Help and FAQ link under HELPFUL INFO.

WARNING: Operating, servicing and maintaining a passenger vehicle or off-highway motor vehicle can expose you to chemicals including engine exhaust, carbon monoxide, phthalates, and lead, which are known to the State of California to cause cancer and birth defects or other reproductive harm. To minimize exposure, avoid breathing exhaust, do not idle the engine except as necessary, service your vehicle in a well-ventilated area and wear gloves or wash your hands frequently when servicing your vehicle. For more information go to

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