Product Information

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What is a Spark Plug & What Does it do?
MCB40-450C
An internal combustion engine requires three key ingredients to operate: air, fuel and spark. A spark plug is a critical engine component that provides the spark that ignites the air-fuel mixture that drives an engine.

A spark plug operates by directing electrical current to flow through a centre electrode, forming a spark across an electrode (or air) gap, completing the circuit to a ground electrode. The centre electrode is surrounded by a ceramic insulator which is non-conductive preventing current leakage and ensuring electricity flows in the desired direction.

Spark Plug Anatomy
Although the spark plug is a familiar engine component, spark plug terminology often varies. The diagram below identifies the major components of a spark plug and their correct terminology.
sparkplug_anatomy
Spark Plug Anatomy

Spark Plug Types
The following table gives an example of the characteristics and service life of resistor spark plugs when used in a modern unleaded engine:

*NGK Spark Plugs are designed to OEM requirements and as such, a variant of each of the above styles may not be available as it may not be an OEM requirement.
**Please note that the service life is provided as a general guide and may vary due to vehicle driving conditions.

What is a Surface Discharge Spark Plug?A surface discharge spark plug is designed to create a spark along the insulator nose at the firing end. This type of spark plug can be further classified into the semi-surface discharge type, supplementary gap type and intermittent discharge type.

Features:

Semi-surface discharge type
The wide gap of semi-surface discharge type improves ignition capability and is less sensitive to voltage requirement increases due to gap growth. Semi-surface discharge plugs burn away the carbon on the insulator nose to suppress a decline of insulator resistance.

Supplementary gap type
Spark discharge at the supplementary gap burns away the carbon on the insulator to suppress a decline of insulation resistance. The small clearance between the insulator supplementary gap prevents the carbon-included combustion gasses from entering the gas volume. This reduces the carbon accumulation on the insulator.

Intermittent discharge type
Spark discharge at intermittent gaps burn away the carbon on the insulator to suppress a decline of insulation resistance.

Part Numbering System
Racing Spark Plugs

*Information in this page, has been sourced from NGK Spark Plugs, www.ngkspark.com.au. Dalby Mower Supplies, is not liable for this information, or what you choose to use it for.

Type* Centre Electrode Ground Electrode Service Life ** Benefits Click Image to Enlarge
Nickel Alloy Nickel Nickel 20,000 – 40,000 kms Standard style Spark Plug Click Image to Enlarge
Iridium IX
Nickel Alloy
(V-Groove)
Nickel Nickel 20,000 – 40,000 kms Improved ignitability due to sparking at periphery of the electrode Click to enlarge
Iridium IX
Iridium IX Iridium tip Nickel 60,000 kms Long service life and even better ignitability due to a small diameter centre electrode Click to enlarge
Iridium IX
Laser Platinum Platinum tip Platinum pad/chip 100,000 kms Extremely long service life. High ignitability due to fine tipped centre electrode Click to enlarge
Iridium IX
Laser Iridium Iridium tip Platinum pad/chip 100,000 kms Extremely long service life. Improved high ignitability due to fine tipped centre electrode Click to enlarge
Iridium IX
NEW
DFE Iridium
(Double Fine Electrode)
Iridium tip Iridium tip 100,000 kms Superior ignitability due to fine tip centre and ground electrodes. Excellent service life. Click to enlarge
Iridium IX

*NGK Spark Plugs are designed to OEM requirements and as such, a variant of each of the above styles may not be available as it may not be an OEM requirement.
**Please note that the service life is provided as a general guide and may vary due to vehicle driving conditions.

What is a Surface Discharge Spark Plug?

A surface discharge spark plug is designed to create a spark along the insulator nose at the firing end. This type of spark plug can be further classified into the semi-surface discharge type, supplementary gap type and intermittent discharge type.
Features:

Semi-surface discharge type

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The wide gap of semi-surface discharge type improves ignition capability and is less sensitive to voltage requirement increases due to gap growth. Semi-surface discharge plugs burn away the carbon on the insulator nose to suppress a decline of insulator resistance.

Supplementary gap type

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Spark discharge at the supplementary gap burns away the carbon on the insulator to suppress a decline of insulation resistance. The small clearance between the insulator supplementary gap prevents the carbon-included combustion gasses from entering the gas volume. This reduces the carbon accumulation on the insulator.

Intermittent discharge type
ss1ss1

Spark discharge at intermittent gaps burn away the carbon on the insulator to suppress a decline of insulation resistance.

Part Numbering System

Part Numbering System1
Part Numbering System

Racing Spark Plugs

R = Racing Serial Number Heat Range

*Information in this page, has been sourced from NGK Spark Plugs, www.ngkspark.com.au. Dalby Mower Supplies, is not liable for this information, or what you choose to use it for.

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