Spark Plugs

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caprihorse
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A spark plug (sometimes in British English a sparking plug, colloquially a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air mixture therein by means of an electric spark, while containing combustion pressure within the engine. [Wikipedia]

When we are getting the car from showroom, that there are inside the engine the most typical spark plugs, which serve at the standard situations very well.

However if, need to increase horse power and torque of your vehicle by tens of HP, special spark plugs are needed to be installed.

There are many OEM spark plug producers that are offering plugs for your vehicle, but sometimes terminology may confuse you.

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Double Platinum
Laser welded platinum tip on centre electrode and platinum tip on the ground electrode. The centre electrode is taper cut which aids in focusing the spark while reducing the voltage necessary to start the combustion process; this will provide better throttle response, improve efficiency and allow a smoother idle. Stainless steel washer reduces plug self-backing.

Platinum
It offers the performance and durability of platinum at a competitive price. The centre electrode is fine wire platinum for better starts, superior acceleration and better fuel economy. Trapezoid cut ground electrode to reduce quenching, is made from a nickel alloy.

Iridium
The iridium centre electrode is both stronger and harder than platinum. This allows an ultra-fine (0.6mm) centre electrode reducing the voltage requirement for spark. This allows for a brighter, stronger spark from your existing ignition system. The ground electrode has a tapered cut at the firing end which reduces quenching for better flame core growth and increased ignitability. The combination of fine wire centre electrode and tapered cut ground will increase performance, improve acceleration, and fuel efficiency.

Iridium vs. Platinum
Iridium is a precious metal that is 6 times harder and 8 times stronger than platinum, it has a 1,200°(F) higher melting point than platinum and conducts electricity better. This makes it possible to create the finest wire centre electrode ever. However platinum alone is no longer enough, ultra long life spark plugs and smaller centre electrodes required harder and stronger precious metals. The strength, hardness and high melting point of iridium makes it very well suited for a fine wire plug and for ultra long life spark plugs. Though better, iridium's not perfect, it is very expensive, and at higher temperatures it oxides, thus rendering pure iridium as an expensively poor choice for spark plug construction. However when blended with other precious metals such as Yttria, Rhodium or Platinum, you can enhance those metals advantages with the superior strength and hardness of Iridium. DO NOT BE FOOLED, ALL IRIDIUM PLUGS ARE NOT THE SAME. Iridium content varies some other brands of iridium plugs are priced lower, (usually due to lower iridium content).

Heat Range
The term spark plug heat range refers to the speed with which the plug can transfer heat from the combustion chamber to the engine head. Whether the plug is to be installed in a boat, lawnmower or race car, it has been found the optimum combustion chamber temperature for gasoline engines is between 500°C–850°C. When it is within that range it is cool enough to avoid pre-ignition and plug tip overheating (which can cause engine damage), while still hot enough to burn off combustion deposits which cause fouling.
The heat range numbers used by spark plug manufacturers are not universal; a 10 heat range in Champion is not the same as a 10 heat range in NGK. Some manufacturers numbering systems are opposite the other, for manufacturers (Champion, Autolite), the higher the number, the hotter the plug. For NGK, the higher the number, the colder the plug.

Typically spark plug needs wrench tool 5/8" (16mm) hex size, long; be sure what the length is needed for your car. In some engines, the coil is directly mounted to plug, so you’ll need also wrench 10mm hex size typically, again long. All the tools should be made from chrome-vanadium metal.

In any case, when you are choosing high performance spark plugs, check with your manufacturer’s handbook (yes, you have it in your car), what they suggest. The information is typically mentioned at the end of the book, at the section related to engine specification.

This is the example for Nissan Pathfinder:

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Before buying some spark plugs at the local market, check at OEM website, if this plug fits to your engine. You probably very well know the situation at the market, where traders are trying to sell you everything, what they have in a stock.

Another story is about ignition coils and cables, which might come later and has also tremendous impact on your engine power.
FSL
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Thanks for the article Silvester.

As I'm currently having issues with my electrical/ignition system so i was doing some research that started with spark plugs... after going through tens of tech forums/websites discussing the famous question copper vs platinum vs iridium i concluded that the marketing gimics used by spark plug manufacturers and misconceptions about the best plug type out of 3 is some what tricky.
After my research it became clear to me that the major difference between these three types of spark plugs is the LIFE OF PLUG.

Iridium being more resistant to corrosion can last much longer than copper plugs, platinum is somewhere in between the two.
There might be practically no difference in power or mileage if you try either of the three types provided they are brand new and gapped accordingly to your engine specifications. So there is no difference on spark size by changing the plug types. So in easy words an iridium plug might go for 70-80,000 Kms and copper plug might only last for 30-40,000 Kms before you need to get a new set

(P.S: These are just random figures to explain the difference)


This brings me to the point how to produce bigger spark, as a bigger spark means more combustion hence more power. The way to achieve this is to install an aftermarket Ignition System like MSD. These ignition systems are capable of producing higher output than the stock ones hence you can play around with the spark plug gaps (increase the gap a bit) which is the how you actually get a bigger spark.

Changing Ignition Coil, Distributor Cap, Rotor and Plug wires will ensure that the spark is used efficiently no matter what ignition system you have, stock or aftermarket (This especially goes for old cars like mine ;)

I hope this helps ;)
Desert Lizard
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Thanks Caprihorse, this is a very useful summary which would save people time to find out information.

I recently changed the standard Champion sparkplugs on the Jeep to slightly better NGK ones, which were incidentally priced the same. The difference in engine output was clearly noticeable but not very significant. I have to mention that the gap was neither measured nor adjusted since the mechanic did not have the tools, nor did I buy them.

Next time, I will go for the better performance plugs, gap them properly and then install them. I think a write up on how to check, gap and install spark plugs would complement your write up..

As for the complete ignition system, I would disagree with FSL for two reasons:
1- The better spark plug would improve performance, not only service life of the spark plug. Think of it as a better quality higher wattage light pulp fixed on the same socket; better light with the same voltage and longer life.
2- The better ignition system (MSD) will deliver electricity to the spark plug in an improved way, which then allows the full utilization of the plugs capability. This is for distributor based engines. For rail based engines, the spark plug is always connected and ignition is controlled by the car's computer. This means no mechanical movement, or disconnection for any reason ie wear or rust, and therefore the only changeable component is the spark plug.
FSL
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DL I agree to the part on old cars, I should admit I have minimal knowledge when it comes to newer technology engines but as i have an old tech engine so I ready about it mostly. The fact is right after people switch from old copper plugs to newer iridium plugs they feel a difference in engine performance reason being the old plugs might have already served their life. The real question if I install new copper plugs and drive it for a day then switch to new iridium plugs, would there be a noticeable difference???

Well my personal answer to that would be NOT NOTICEABLE difference.

Even i did my homework comparison on copper and iridium as metals, turns out Copper is one of the best metals in terms of electrical conductivity. Only advantage that the Iridium/Platinum plugs will offer over the standard Copper plugs is useable lifespan, provided that the plugs are of similar design. There is no correlation between electrode material and HP of the engine.

So the marketing claims of fuel economy or power gains from a plug - about 99% is bogus. A better plug cannot generate more power - it might be more efficient with the available ignition power at hand, but cannot MAKE power. Nothing wrong running a more expensive plug - will not hurt anything. Completely up to you and how often you want to replace the plugs.

Your example is i guess not valid for spark plugs comparison as the only difference between spark plugs is their core metal (copper, platinum or iridium) which channels current from one end to the other (which is the purpose of a spark plug). So if current is of same power the plug cannot enhance it. Same goes for old engines or newer engines (i guess the computer keeps the current value constant no matter what spark plug you use)
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caprihorse
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OK, guys, I appreciate your comments.

Now to DL's reply:

The computer in the car is controlling the timing of the spark, not the intensity. The size of the spark is only based on the quality of spark plug and additional power supplied, e.g. by MSD. NGK is selling spark plugs valued around 5 Dhs also, so this is not measurement of the car's power improvement. Normally really you should check the top performance spark plugs specification for your engine before installing them, the high performance plugs are starting at 35 Dhs per piece. No need to check for gap between electrodes as they come from factory set to the proper dimension. Definitely 'double metal' is the hit, as the precious metal is applied to both electrodes.

FSL:
Copper has electrical resistivity (20 °C) 16.78 nΩ·m, where Iridium has (20 °C) 47.1 nΩ·m and Platinum has (20 °C) 105 nΩ·m. However the melting point for Copper is 1084.62 °C, for Iridium 2466 °C and Platinum 1768.3 °C.
The optimum combustion chamber temperature for gasoline engines is between 500°C–850°C. At this temperature copper top electrode tends to bent and the gap will change over the time, so it will not produce optimal spark intensity. Additionally sparking corrosion will appear also on both electrodes. So this is the answer, why copper spark plugs should be changed every 10,000 km.

If you check spark plugs after a time visually, it should have dark red/brown colour around electrodes. If it does not have, there is something wrong with the supplied voltage or problem in combustion chamber.

If you did not notice any change in performance, after changing spark plugs, it is probably that you changed good for good or bad for bad.

From the beginning my car, Pathfinder, was maintained by agency and at regular service I was asking about the type of spark plugs installed in my engine. I was ensured that they are Platinum. At 100,000 service, did by me, I purchased new double platinum as original Nissan part from the dealer and removed old. To my surprise old spark plugs were cheap copper…

After the change I noticed immediately increase in the power and less fuel consumption. Earlier I could hardly do 200km in the desert on the full tank, now I can do 300km; earlier majority of the climbing I was doing on the 1st gear, now I can easily do it on the 2nd gear.
Longer trips on full tank show also on standard highway or city drives, exceeding 100km comparing with the previous regime.

On the recent trip to Liwa, my buddy’s FJ was asking to refill the tank on the track (the famous E light alarm), where my tank was showing about ¼ full.

Excellent explanation on spark plugs is also here - http://en.wikipedia.org/wiki/Spark_plug.
FSL
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Thanks for further explanation Silvester...
So here is my conclusion but correct me if I'm wrong...

a new set of copper spark plugs will out-perfrom a new set of iridium plugs, However after couple of thousand KMs the copper will start losing it's life (performance) but the iridium will keep on going with consistent performance for a longer life.

What do you say?
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caprihorse
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I appreciate the interest, Faisal.

Copper spark plugs are the worse option, due to their stability, corrosion, melting and low durability. You have to pay attention also to the shape of central electrode to get a proper corona discharge. Electrical resistivity is one parameter for the low resistance in the wires inside the spark plug, but then it is important what metal is applied to the tips of electrodes, to achieve the most effective discharge.

The best option is dual precious metal, platinum or iridium, because of more intensive spark, due to the shape of central electrode. There is still lots of copper inside the spark plug, but the end of the tip makes the story.

The best, from my opinion is surface-discharge spark plug, because of life-time stability of the gap and the variations in spark path.

If you still have a spare time, pls read Wikipedia article carefully :057:
FSL
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Thanks Silvester, actually i spent a lot of time last week trying to figure out which one is the best :057: and we never met personally in the mean time otherwise I'd definitely discussed it with you.

But thanks for the technical explanation :047:
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caprihorse
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What is exact model of your car and VIN? I'll try to figure out something for you :060:
Wasif Ahmed
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Go with the Iridium opion....far superior performance and life with hardly any pitting or corosionof the points....never need to adjust the agp once fitted.

There is also the heat range of the plug to consider.....there are "hot" plugs and then tere are "cold" plugsout there.

An iteresting thing on an FJ Cruiser is that they come with two seperate brands of spark plugs intaled one the engine from the factory...one brand on the left bank and another brand on the right bank ! This is something to do with the design of the engine and the heat range
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