Warnings and precautions regarding safety and usage
Be sure to read this Catalogue & Website
IN NO EVENT SHALL DENSO BE LIABLE FOR ANY LOSSES, EXPENSES OR DAMAGES WHATSOEVER RESULTING FROM ANY OF THE FOLLOWINGS;
- FAILURE TO COMPLY WITH THE WARNING OR PRECAUTIONS DESCRIBED IN THIS CATALOGUE AND WEBSITE,
- ANY USES OTHER THAN THE APPLICABLE USE DESCRIBED IN THIS CATALOGUE AND WEBSITE, and
- ANY TROUBLE NOT ATTRIBUTABLE TO DENSO SPARK PLUGS.
*“Spark plugs” means any type of DENSO's spark plugs, including but not limited to Iridium Power, Iridium TT, Iridium Racing, Iridium Plus, and Iridium Tough, Iridium Long Life, Double Platinum, U-Groove, Resistor, Standard, Nickel TT, Platinum TT, Two-Tops.
WARNING (Prohibited Usage)
- Never use DENSO spark plugs in the engines for any aircraft, including airplanes, helicopters, gliders and drones. The DENSO spark plugs sold are not designed and manufactured for any aircraft: use may result in a plane crash or other accidents due to engine malfunction.
- Never use DENSO spark plugs, listed in this catalogue, in the engines for generator and gas heat pump air conditioning system. The DENSO spark plugs we sell are not designed and manufactured for such use, so that such use may result in accidents, including power generation stop or heat generation stop. A separate catalogue for DENSO spark plug specifically designed for generators (gas engines) is available. Please contact your DENSO representative for more information.
- Never use DENSO spark plugs for gas burner ignition. The DENSO spark plugs we sell are not designed and manufactured for such use, so that such use may result in ignition failure or equipment damage due to overheating.
- Be sure to turn off the engine and disconnect the battery before replacing or adjusting the plugs. Failure to heed this warning may result in a fire, an electric shock and/or bodily harm.
Spark Plug Handing Precautions
- Always refer to the vehicle manufacturer's repair manual for specific installation procedures.
- Carefully read the instructions and precautions on the package, catalogue and website.
- Do not drop spark plugs. This may cause the spark plug to crack internally or the gap to be narrowed, preventing it from functioning correctly.
- If Spark Plug needs to be gapped, bend from the back of the ground strap with appropriate tools. Do not physically adjust gap using the center electrode as leverage. Check gaps with care, not to damage the center electrode. Gap to the vehicle specific manufacturer's recommendation unless otherwise recommended.
Modified Vehicles and Tuning Precautions
- DENSO will not bear any responsibility whatsoever for any trouble arising from mechanically or electronically modified engines or vehicles.
- It is the user's judgement and responsibility to check the specifications required for modified engines, which includes and not limited to, gapping, heat ranges, reach, projection, and/or clearances with valves and/or pistons.
Catalogue & Website Precautions
- Precautions for cross reference and product tables showing other manufacturer's spark plugs:
- Use for reference only. Table does not guarantee the performance of spark plugs when installed in the vehicles if plug was specified using cross references. Always check the applications section for DENSO recommended plugs.
- The spark plug specifications (construction, material, etc.) differ from one manufacturer to another.
- Select a suitable type of spark plug from the vehicle application table. If not listed on the table, please check with your DENSO Representative.
- The contents of the catalogue and website are updated on a regular basis, but they cannot account for daily dynamic changes such as new applications and or OE supersessions. If there is an issue with the information, please contact your DENSO Representative for further assistance.
- Consumption tax and installation fees are not included in the price of the product.
- Some spark plugs on this catalogue and website are manufacturer's genuine parts that listed for reference and cannot be directly sold. Please contact your DENSO representative for further assistance.
- The appearance and specifications of the product are subject to change without prior notice.
- The images of spark plugs indicated in the catalogue and website are conceptual diagrams, and sometimes differ from the actual products.
Precautions for selecting spark plugs.
When selecting an appropriate type of spark plug, check the vehicle manual, the maintenance manual and the application table in this catalog, and select spark plugs with the correct dimensions and heat range.
Know-how concerning spark plug selection
- Basically, use a spark plug that has a standard heat range. Note, however, if this type of spark plug is used for traveling at low speed or traveling over short distances, resulting in the occurrence of carbon fouling, it is recommended that you use spark plugs that have a low heat range.
- Do not use a non-resistor type plug in an engine for which a resistor type plug is specified. This may result in engine trouble due to noise accompanying the spark discharge.
- If you install extended type spark plugs (J, QJ, KJ, PKJ, SKJ, VKJ, TJ, etc.) in a non-desiganated engine, they may interfere with the valves and pistons, causing damage to the engine and the spark plugs.
Tuned or modified vehicle
- In the case of a tuned or modified vehicle which has a modified engine, or one which uses a muffler, ignition coil, plug cords, turbo unit or commercially available electronic ignition system, or a NOS ( * ) for example, it is necessary to increase the heat range of the plugs to a value that matches the tuning level. If you do not select the plugs correctly, trouble such as carbon fouling / oil fouling or pre-ignition (a naturally occurring phenomenon in which combustion occurs prior to the emission of a spark from the plug) will occur, which may result in a breakdown of the vehicle.
( * ) NOS: A device which injects nitrous oxide together with gasoline into the air intake in order to increase the engine power
- When using a tuned vehicle or a modified vehicle, select a heat range using your own judgment and at your own responsibility.
When using Iridium Racing plugs
- Iridium Racing plugs are intended for racing and also for tuning up. Set the heat range of the plugs to match the tuning level, based on the heat range of the standard plugs or Iridium Power plugs.
- Generally, a plug that protrudes into the combustion chamber has superior ignition performance, resulting in improved engine performance. On the other hand, this type of plug is liable to be exposed to the high-temperature combustion gas, and also the length of the grounding electrode increases, reducing the heat resistance and durability of the plug. For this reason, the higher the tuning level becomes, the greater is the necessity to use a type of plug that has a recessed electrode.
- Generally, when the tuning level rises, the necessity of using high heat range plugs increases.
- When using Iridium Racing plugs, select them according to your judgment and at your own responsibility.
Selection of the optimum heat range
Using a plug fitted with a terminal nut
If you use a plug fitted with a terminal nut when the terminal nut is loose, the engine is likely to malfunction. If the part No. of the plug includes the notation "R" alongside "Terminal shape" or "NUT," and the plug is used with the terminal nut fitted, securely tighten the nut using pliers, or the like. In the case of a plug whose part No. includes the notation "RC" alongside "Terminal shape" or "NUT," the terminal nut is crimped and will not work loose under normal applications. However, if vibration of the engine and/or the plug cord is severe, the nut may on rare occasions become loose. Keep this possibility in mind, and periodically inspect the nut. If it is loose, re-tighten it securely.
Precautions to observe when installing the spark plugs
Recommended torque and angle of rotation
It is necessary to install the plugs in the engine using the correct torque. Note that if the torque is too low, the plugs are liable to work loose due to leakage of combustion gas or vibration, resulting in possible damage to the engine and the plugs. Conversely, if the torque is too high, the crimping between the insulator and the housing is liable to become loose, causing the integrity of the seal to be impaired or the mounting screw thread to break.
- Use the correct wrench that matches the hex part of the plug. Take care not to damage the insulator.
- When carrying out this work, take steps to ensure that oil, dust and foreign objects in the vicinity of the cylinder head do not enter the engine.
- Before installing the plug, clean the mounting seat on the engine side, check that there is a gasket, and then insert the plug into the mounting seat.
- When carrying out this work, hold the plug vertically, and then lightly tighten it by hand or by using a plug wrench.
- Next, using a plug wrench, tighten the plug to the recommended torque or the recommended angle indicated in the table below.
If you tighten the plug to a greater rotation angle or torque than that indicated in the table below, the engine may become damaged or the screw thread of the plug may break, so be careful.
If you apply grease or another screw thread lubricant to the threaded part of the plug, you are liable to tighten the plug to an excessive degree, impairing the integrity of the seal, even if you apply no more than the recommended torque. For this reason, do not coat the plug with screw thread lubricant.
If you apply the plug wrench obliquely, an unreasonable force may be applied to the insulator, causing it to crack, as indicated in the figure below. For this reason, be careful not to hold the wrench obliquely.
|Thread Size||Reccommended Touque||Applicable Models||Reccommended Tightening Angle|
|New Plug||Previously Used|
|M 8||8-10N･m||All Types||About 1/3 turn||About 1/12 turn|
|M10||10-15N･m||Type other than the ones shown below||About 1/3 turn||About 1/12 turn|
|M10||10-15N･m||UFE, IUH, VUH, VNH Types||About 2/3 turn||About 1/12 turn|
|M10||10-15N･m||Stainless Gasket Type(*1)||About 3/4 turn||About 1/12 turn|
|M12||15-20N･m||All Types||About 1/3 turn||About 1/12 turn|
|M14||20-30N･m||Type other than the ones shown below||About 1/2 turn||About 1/12 turn|
|M14||20-30N･m||Stainless Gasket Type(*2)||About 2/3 turn||About 1/12 turn|
|M18||30-40N･m||All Types||About 1/4 turn||About 1/12 turn|
|10-20N･m||All Types||About 1/16 turn||About 1/16 turn|
|20N・m||If the cylinder head material is cast iron||-||-|
|17.5N・m||If the cylinder head material is aluminum||-||-|
|30N・m||If the cylinder head material is cast iron||-||-|
- (*1) VUH27ES, U24FER9S
- (*2) IK16G, IK20G, IK22G, K20PR-U8S, K20PR-U9S, KJ20DR-M11S, PK22PR-L11S, SK20PR-N9S, SK22PR-M11S, SKJ20DR-M11S, VK16G, VK20G, VK22G
Cracking of the insulator
The plugs of recent engines are installed in deep plug holes, so it may be difficult to notice whether or not you are holding the wrench obliquely when installing or removing the plugs. However, if you turn the wrench in this condition, the head of the insulator may stick , causing an unreasonable force to be applied to it. As a result, the insulator is liable to crack.
*However, the mode of occurrence differs according to the construction and dimensions of the plug holes in the engine, and also the type of wrench used.
Regarding the spark plug replacement timing
The electrode progressively wears, causing the spark gap to increase, along with the increasing number of spark discharges. When the gap exceeds a certain limit, the sparking performance deteriorates, which may prevent stable ignition of the gas mixture. When this happens, the horsepower of the engine falls, the fuel economy deteriorates and also the quality of the exhaust gas is adversely affected, so it is necssary to replace the plugs. The table below shows our recommended plug replacement timing as a rough guide to the economic life of the plugs. The economic life may be reduced depending upon the vehicle running condition* and the sparking characteristics*.
Rough guide to the recommended replacement interval (economic life) for conventional spark plugs
|Automobile||15,000 to 20,000km|
|Motorcycle||3,000 to 5,000km|
Rough guide to the recommended replacement interval (economic life) for platinum plugs, Iridium Tough and Iridium Plus plugs
|Automobile||up to 100,000km *1|
|Motorcycle||There are no settings.|
*1: The small engine vehicle, a tuned vehicle or a vehicle that uses a simultaneous ignition coil is often used at high speed. This may cause the life of the plugs to be reduced.
Rough guide to the recommended replacement interval (economic life) of Ni-TT plugs
|Automobile||15,000 to 20,000km|
|Motorcycle||There are no settings.|
*Factors which shorten life
- Running condition: High-speed running, high-load running, hill climbing, extended idling (taxi), etc.
- Ignition characteristics: Simultaneous ignition, positive discharge, use of high-energy coil, etc.
- *Use the genuine plug for special applications such as ambulances, patrol cars, etc.
Simultaneous ignition system
A simultaneous ignition system is an ignition system in which two plug cords are connected to one coil, as shown in the figure. A normal coil consists of a single coil which provides a high voltage to one plug. Generally, it employs a negative discharge that results in relatively low wear. In contrast, a simultaneous ignition system uses a single coil which must be capable of supplying high voltage to two plugs. A negative discharge occurs at one plug and a positive discharge occurs at the other plug, resulting in the generation of wasteful fire that is unrelated to combustion. For this reason, the electrode at which a positive discharge occurs tends to wear markedly.
Adjustment of the plug gap
- If the center electrode becomes rounded or the grounding electrode wears unevenly, replace the plug with a new one.
- Do not adjust the gap of a plug that has a thin electrode, such as a platinum plug or an iridium plug, because this may result in damage to the center electrode.