NGK Iridium IX Spark Plug Box of 4 (CPR7EAIX-9)

0.6mm Iridium Fine Wire Ignition in a Box of Four NGK CPR7EAIX-9 Plugs

The NGK CPR7EAIX-9 Iridium IX spark plug (NGK9198) is engineered for performance enthusiasts who demand consistent ignition, improved throttle response, and extended service life beyond what standard nickel alloy plugs can deliver. The 0.6mm iridium fine wire center electrode produces a concentrated, stable spark with minimal voltage demand, while the tapered cut ground electrode reduces quenching for stronger combustion at every RPM. Sold as a box of four, NGK9198 is a direct replacement for applications specifying the M10 x 1.0mm thread, 19mm reach, heat range 7 plug with a gasket seat.

Key Features

• 0.6mm iridium fine wire center electrode for a concentrated, stable spark
• Iridium alloy melting point far exceeds platinum, delivering up to 50,000-mile service life
• Iridium center electrode is six times harder and eight times stronger than platinum
• Tapered cut ground electrode reduces quenching and improves ignitability
• Solid copper core provides superior heat dissipation across a wide heat range
• Trivalent metal plating offers anti-corrosion and anti-seizing protection
• Corrugated ribs on the insulator prevent flashover
• Pure alumina silicate ceramic insulator for superior strength and thermal transfer
• Triple seals prevent combustion gas leakage
• 5k Ohm resistor suppresses EMI/RFI interference
• Factory pre-gapped at 0.035 in (0.9mm)
• Sold as a box of four plugs

Specifications

What's Included

• 4 x NGK CPR7EAIX-9 Iridium IX Spark Plugs

Frequently Asked Questions

In the NGK naming system: C indicates the thread diameter (10mm), P indicates the projected insulator tip, R indicates a built-in resistor, 7 is the heat range, E indicates the thread reach (19mm), A is the thread pitch (1.0mm), I indicates the iridium center electrode, X indicates a tapered cut ground electrode, and 9 indicates the pre-set gap (0.9mm). Together these define a 10mm, 19mm reach, resistor, iridium IX plug with a tapered cut ground and a 0.9mm gap.

NGK rates the Iridium IX series for up to 50,000 miles of service. Actual longevity depends on engine type, fuel quality, oil consumption, and operating conditions. Modified or forced-induction engines running rich or with increased cylinder pressure may shorten service intervals.

NGK does not recommend gapping Iridium IX plugs after the factory pre-set. The 0.6mm iridium center electrode is extremely fine and can be damaged or fractured by gapping tools. The NGK9198 arrives pre-gapped at 0.035 in (0.9mm) and should be installed as-is unless your specific application requires a different gap and you use an appropriate thin wire gauge tool with extreme care.

NGK Iridium IX uses an iridium fine wire center electrode with a nickel taper cut ground electrode and is designed for performance and modified applications. NGK Laser Iridium uses iridium on both the center and ground electrodes, making it a more premium OEM-replacement option. Platinum plugs use a platinum tip center electrode, which is softer than iridium, and are generally positioned as a mid-grade upgrade over standard copper plugs.

Yes. The R in the NGK part number indicates a built-in 5,000-ohm resistor. The resistor suppresses electromagnetic interference (EMI) and radio frequency interference (RFI) that can affect onboard electronics, sensors, and ignition control modules in modern vehicles and powersports equipment.

For cast iron cylinder heads, torque to 7.2 to 10.8 lb-ft. For aluminum cylinder heads, torque to 7.2 to 8.7 lb-ft. Always install plugs finger-tight first to confirm threads are not cross-threaded before applying final torque. Do not overtighten, as this can crush the gasket seat excessively and damage the plug or head threads.

The NGK Iridium IX series is suitable for modified and performance applications including mild forced induction. For high-boost or high-cylinder-pressure applications, a colder heat range plug may be needed to prevent pre-ignition. Consult your engine builder or tuner to confirm heat range suitability for your specific power level and boost pressure.

Most four-cylinder engines require four spark plugs for a complete service. Selling NGK9198 as a box of four allows you to complete a full spark plug replacement in a single purchase without needing to order multiple individual units, reducing shipping costs and ensuring a matched set from the same production batch.

Installation Instructions

1. Allow the engine to cool fully before beginning spark plug replacement to avoid burns and thermal thread damage.
2. Remove the ignition coil or spark plug wire from each plug location.
3. Use a spark plug socket (5/8 in / 16mm) with a ratchet and extension to loosen and remove each existing plug.
4. Inspect the old plugs for signs of oil fouling, overheating, or unusual wear that may indicate an underlying engine issue.
5. Thread each NGK CPR7EAIX-9 plug in by hand first to confirm proper thread engagement and avoid cross-threading.
6. Torque to 7.2 to 10.8 lb-ft for cast iron heads or 7.2 to 8.7 lb-ft for aluminum heads.
7. Reconnect each ignition coil or spark plug wire, ensuring a firm connection.
8. Start the engine and verify smooth idle with no misfire codes before returning to service.

WARNING: This product can expose you to chemicals including lead and phthalates, which are known to the State of California to cause cancer and reproductive harm. For more information go to www.P65Warnings.ca.gov.