Updated August 2013
References:
Denso: http://www.densoautoparts.com/spark-plugs
NGK USA: http://ngksparkplugs.com
NGK Canada: http://www.ngksparkplugs.ca
An NGK vendor: http://sparkplugs.com
'06 FSM
The following plugs are OEM fitments.
2004 to 2005, 2.0 L and 2.3 L Engines
NGK Laser Iridium ITR6F13
Equipped with an iridium-tipped, taper cut, fine wire center electrode and a welded-on platium pad ground electrode, this 17.55 mm (.691") reach plug is pre-gapped at 1.25 mm to 1.35 mm (.050" to .053") with a heat range of 6.
2006 to 2009, 2.0 L and 2.3 L Engines
NGK Laser Iridium ILTR5A-13G
Equipped with an iridium-tipped, taper cut, fine wire center electrode and a welded-on platinum pad ground electrode, this 25 mm (.984") reach plug is pre-gapped at 1.25 mm to 1.35 mm (.050" to .053") with a heat range of 5. This is the only replacement spark plug listed in the FSMs.
Mazdaspeed 3, 2.3 L DISI, L3-VDT Engine
NGK Laser Iridium ILTR6A-8G
Equipped with an iridium-tipped, taper cut, fine wire center electrode and a welded-on platinum pad ground electrode, this 25 mm (.984") reach plug is pre-gapped at .8 mm (.032") with a heat range of 6. Note that the spark plug is one heat range colder, and utilizes a smaller electrode gap than the one above for the 2006 to 2009 normally aspirated engines.
According to NGK, the iridium center electrode which is both stronger and harder and has a higher melting point temperature than platinum, along with the platinum-tipped ground electrode, contribute toward the extreme longevity of the above-listed plugs. Consequently, as listed in the FSMs, the factory recommended spark plug replacement interval for both USA Normal Driving Conditions (Schedule 1) and USA Unique Driving Conditions and Canada all driving conditions (Schedule 2) is 75,000 miles (120,000 km).
According to the FSM, unique driving conditions include the following:
Repeated short-distance driving
Driving in dusty conditions
Driving with extended use of brakes
Driving in areas where salt or other corrosive materials are used
Driving on rough or muddy roads
Extended periods of idling or low-speed operation
Driving for long periods in cold temperatures or extremely humid climates
Mazdaspeed 3s may require more frequent plug replacement so those owners should check a suitable source for that information.
In addition to the longevity factor, there are at least two other advantages to using this type of plug. First, the extra hardness and higher melting point temperature of the iridium center electrode allows it to be made smaller in area which reduces the voltage required to initiate a spark. This is because electron emission is increased when it takes place from a sharp point, or edge, or from a smaller curvature radius. This allows for a brighter, stronger, higher energy spark from the existing ignition system. In fact, a needle-shaped electrode would provide maximum electron emission but would quickly burn away in the combustion chamber environment. Second, the smaller center electrode surface functions to reduce the phenomenon known as quench by reducing the contact (surface) area between the electrode and the spherical flame front enabling it to more easily move outward into the combustion chamber to initiate the flame propagation phase of the combustion process.
NGK Spark Plug Nomenclature
The alpha-numeric characters used in NGK spark plug nomenclature are used to denote specific properties. NGK uses certain design symbols arranged in certain orders to specify a spark plug's characteristics.
In this instance, the first letter in the series denotes the plug type; I denotes a plug with iridium/platinum electrodes.
The following letter, or letters, denote the plugs reach (length of the threaded portion of the plug) and/or its construction type. This is not the same property as the length of the insulator, or tip, of the plug (its projection). In this case, the letter L may denote a reach of 25 mm, for example.
The first numeral in the series displays the heat range of the plug. In Japanese plugs, the higher the number the colder the plug. Plugs numbered 6 are one heat range colder than those numbered 5. FYI, Denso 16 is equivqlent to NGK 5 and 20 is equivalent to 6.
Finally, the last numeral(s) in the series, or beyond the hyphen, specifies the electrode gap. Some examples: 13 = 1.3 mm (.052"); 11 = 1.1 mm (.044"); and 8 = .8 mm (.032").
For a more detailed explanation of NGK's design symbols for spark plugs, go to:
Happy Motoring!
References:
Denso: http://www.densoautoparts.com/spark-plugs
NGK USA: http://ngksparkplugs.com
NGK Canada: http://www.ngksparkplugs.ca
An NGK vendor: http://sparkplugs.com
'06 FSM
The following plugs are OEM fitments.
2004 to 2005, 2.0 L and 2.3 L Engines
NGK Laser Iridium ITR6F13
Equipped with an iridium-tipped, taper cut, fine wire center electrode and a welded-on platium pad ground electrode, this 17.55 mm (.691") reach plug is pre-gapped at 1.25 mm to 1.35 mm (.050" to .053") with a heat range of 6.
2006 to 2009, 2.0 L and 2.3 L Engines
NGK Laser Iridium ILTR5A-13G
Equipped with an iridium-tipped, taper cut, fine wire center electrode and a welded-on platinum pad ground electrode, this 25 mm (.984") reach plug is pre-gapped at 1.25 mm to 1.35 mm (.050" to .053") with a heat range of 5. This is the only replacement spark plug listed in the FSMs.
Mazdaspeed 3, 2.3 L DISI, L3-VDT Engine
NGK Laser Iridium ILTR6A-8G
Equipped with an iridium-tipped, taper cut, fine wire center electrode and a welded-on platinum pad ground electrode, this 25 mm (.984") reach plug is pre-gapped at .8 mm (.032") with a heat range of 6. Note that the spark plug is one heat range colder, and utilizes a smaller electrode gap than the one above for the 2006 to 2009 normally aspirated engines.
According to NGK, the iridium center electrode which is both stronger and harder and has a higher melting point temperature than platinum, along with the platinum-tipped ground electrode, contribute toward the extreme longevity of the above-listed plugs. Consequently, as listed in the FSMs, the factory recommended spark plug replacement interval for both USA Normal Driving Conditions (Schedule 1) and USA Unique Driving Conditions and Canada all driving conditions (Schedule 2) is 75,000 miles (120,000 km).
According to the FSM, unique driving conditions include the following:
Repeated short-distance driving
Driving in dusty conditions
Driving with extended use of brakes
Driving in areas where salt or other corrosive materials are used
Driving on rough or muddy roads
Extended periods of idling or low-speed operation
Driving for long periods in cold temperatures or extremely humid climates
Mazdaspeed 3s may require more frequent plug replacement so those owners should check a suitable source for that information.
In addition to the longevity factor, there are at least two other advantages to using this type of plug. First, the extra hardness and higher melting point temperature of the iridium center electrode allows it to be made smaller in area which reduces the voltage required to initiate a spark. This is because electron emission is increased when it takes place from a sharp point, or edge, or from a smaller curvature radius. This allows for a brighter, stronger, higher energy spark from the existing ignition system. In fact, a needle-shaped electrode would provide maximum electron emission but would quickly burn away in the combustion chamber environment. Second, the smaller center electrode surface functions to reduce the phenomenon known as quench by reducing the contact (surface) area between the electrode and the spherical flame front enabling it to more easily move outward into the combustion chamber to initiate the flame propagation phase of the combustion process.
NGK Spark Plug Nomenclature
The alpha-numeric characters used in NGK spark plug nomenclature are used to denote specific properties. NGK uses certain design symbols arranged in certain orders to specify a spark plug's characteristics.
In this instance, the first letter in the series denotes the plug type; I denotes a plug with iridium/platinum electrodes.
The following letter, or letters, denote the plugs reach (length of the threaded portion of the plug) and/or its construction type. This is not the same property as the length of the insulator, or tip, of the plug (its projection). In this case, the letter L may denote a reach of 25 mm, for example.
The first numeral in the series displays the heat range of the plug. In Japanese plugs, the higher the number the colder the plug. Plugs numbered 6 are one heat range colder than those numbered 5. FYI, Denso 16 is equivqlent to NGK 5 and 20 is equivalent to 6.
Finally, the last numeral(s) in the series, or beyond the hyphen, specifies the electrode gap. Some examples: 13 = 1.3 mm (.052"); 11 = 1.1 mm (.044"); and 8 = .8 mm (.032").
For a more detailed explanation of NGK's design symbols for spark plugs, go to:
Happy Motoring!