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Old 12-17-2011, 12:31 PM   #16
bikyto
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Thanks v-rider for the explanation
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Old 12-17-2011, 02:51 PM   #17
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Quote:
Originally Posted by V-rider View Post
In an attempt to slow the spread of misinformation...
Great explanation. Thank you for taking time to write it.
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Old 12-18-2011, 12:17 AM   #18
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Thanks V-rider for the info, but still have more questions...

In an attempt to slow the spread of misinformation...

A precious metal (platinum or iridium), fine electrode spark plug design was created to be more durable under high temperatures than the common nickel plug design.

If your cylinder temperatures are too high then your spark plug firing end temperature could also be too high. It doesn't matter which design of plug you have in there - regular or fine electrode - both will be damaged if you experience pre-ignition (not to be confused with knock). But iridium spark plugs withstand better in high cylinder temperatures if yjere is no pre-ignition?
(By the way, the term "detonation" is sometimes used interchangeably with knock, but knock is the more correct term. Knock is different from the phenomena called pre-ignition.) Your engine will most likely suffer severe damage if you experience pre-ignition. I am not familiar with these terms. I thought detonation is what happens at the exaust reason being very poor mixture, knock caused by too much advance for the given gas and pre ignition is???

The firing end ceramic insulator shape is what mainly determines the heat range of the spark plug. The heat range is the most important factor to consider when replacing your plugs. Just don't install a heat range hotter than what is recommended - you will risk pre-ignition. So what is the heat range of a spark plug. Is it related to the temp the spark plug can endure or the length of the spark or what?

Along with durability, the fine electrode design also provides better ignitability.
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Old 12-18-2011, 03:16 AM   #19
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Your confusing me too.

Quote:
Originally Posted by V-rider View Post
In an attempt to slow the spread of misinformation...

I think your mechanic may be confusing two different possible issues. "Damage" and durability are two different things.

A precious metal (platinum or iridium), fine electrode spark plug design was created to be more durable under high temperatures than the common nickel plug design. That's one major reason why they are made! Auto and powersport manufacturers prefer to use this design if their bean-counters will let them.

If someone has "high motor temperatures" then they have more to worry about than the firing end design (or material) of their spark plugs. OK

If your cylinder temperatures are too high then your spark plug firing end temperature could also be too high. It doesn't matter which design of plug you have in there - regular or fine electrode - both will be damaged if you experience pre-ignition (not to be confused with knock).
That’s called advanced ignition or timing, i.e. spark fires before TDC.

As I understand it, pre-ignition is just that, normally caused by a hot spot in the combustion chamber, bit of shit or too hot a plug that glows red and ignites the fuel/air mixture before spark.

(By the way, the term "detonation" is sometimes used interchangeably with knock, but knock is the more correct term. Knock is different from the phenomena called pre-ignition.) Your engine will most likely suffer severe damage if you experience pre-ignition.

Engine knock is caused by either too high compression ratio for the fuel/air mixture, i.e. too low amounts of octane in the fuel, octane is added to petrol to increase its compressibility before itself ignites, we want spark plug to do that.

The firing end ceramic insulator shape is what mainly determines the heat range of the spark plug. The heat range is the most important factor to consider when replacing your plugs. Just don't install a heat range hotter than what is recommended - you will risk pre-ignition.

I don’t agree, the main reason for plugs to have a heat range is to keep um clean. When a plug runs at the “correct temperature” is far less prone to fouling, go to hot it can result in pre-ignition but if your plugs are fouling up, going up one on the heat range is advisable, misfiring is not good for engines.

The metal electrode shape or material really has nothing to do with the heat range

Err kind of agree, as I was told, there are two parts to the electrode, one which is made from steel. Steel conducts electricity and is magnetic but is it gets too red hot it becomes austenitic, doesn’t like to conduct electricity and becomes nonmagnetic so becomes more an insulator. This is safety for your engine because it will promote a miss and cool the motor down.

- but the precious metal, fine electrode design will last longer.

Along with durability, the fine electrode design also provides better ignitability.

Most engine designs will respond favorably to a plug with better ignitability. If you don't notice a difference using your five senses - then probably only a gas analyzer will show the improvement. If that is the case, and you don't care how long it is between your plug replacement intervals, then don't bother spending the extra money.

I run NGK iridium plugs. I get them cheap because I am a Test Engineer for NGK (not bragging - just throwing that out there to lend credibility to my words.)

I’m a test engineer for Armitage Shanks, gives me no credibility.

OK. Nuff said. Thanks for reading.

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Old 12-18-2011, 08:16 AM   #20
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Great discussion. From what I gather, it seems to makes sense to install iridium plugs. Or am I wrong ?
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Old 12-18-2011, 10:19 AM   #21
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OK....put the Iridiums in my KTM Adventure last night...my original post was from past experience with another bike...

After doing the Valve Check and putting in the Iridiums-CR8EIX, here is what I now have personal experience with seat time-

1-Crisper Accelleration
2- Better Low End Torque

3- Gas Mileage to be determined after a couple of Tanks...
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Old 12-18-2011, 11:27 AM   #22
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Quote:
Originally Posted by AdvGa View Post
OK....put the Iridiums in my KTM Adventure last night...my original post was from past experience with another bike...

After doing the Valve Check and putting in the Iridiums-CR8EIX, here is what I now have personal experience with seat time-

1-Crisper Accelleration
2- Better Low End Torque

3- Gas Mileage to be determined after a couple of Tanks...
Could all these be due to new plugs no matter what they are? Kind-of seat of pants difference after putting new oil.
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Old 12-18-2011, 11:34 AM   #23
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Could all these be due to new plugs no matter what they are? Kind-of seat of pants difference after putting new oil.
...no, since Iridiums in other bikes (Non-KTM) performed the same way.

Also, normal plugs are good to about 8-15k miles where Iridiums are good to about 20-40k miles and the Harder Metal materials don't degrade as fast and as mentioned above, easier on the Ignition System.
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Old 12-18-2011, 02:29 PM   #24
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...no, since Iridiums in other bikes (Non-KTM) performed the same way.
That doesn't exclude the possibility that it could be due to the fact that it are new spark plugs.
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Old 12-18-2011, 03:05 PM   #25
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Quote:
Originally Posted by AdvGa
...no, since Iridiums in other bikes (Non-KTM) performed the same way.
Quote:
Originally Posted by Schannulleke View Post
That doesn't exclude the possibility that it could be due to the fact that it are new spark plugs.
Not say they make that much difference, but iridium is one of those strange metals, very high melting point, very dense but brittle and almost a superconductor at low temperatures. Oh bloody expensive too.
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Old 12-18-2011, 03:47 PM   #26
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FWIW I use iridium plugs in my bikes including the 2 stroke, also I gap them to around 1.1mm, bigger gaps mean more energy and a better, more consistent start to the burn, the very thin iriduim electrode means less voltage is required to fire the plug for a given gap, so since you have lets say 40kv available increasing the gap makes more use of that. The manufacturers make some use of this typically I notice the iriduim gaps are slightly (0.1 to 0.2mm) bigger than copper cored plugs.
The iridium plugs definitely make a difference but show up most when the mixture is difficult to ignite i.e. cold, too much egr or too lean and the difference can be significant there.
So they get my vote.
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Old 12-18-2011, 07:29 PM   #27
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Here are a few sites to look at - may help clear up some misconceptions.

Check this out charlie264. May help clear up things:

http://www.ngk-elearning.com/

http://www.ngksparkplugs.com/tech_su...x.asp?mode=nml


A few more quick answers:

"Engine knock is caused by either too high compression ratio for the fuel/air mixture, i.e. too low amounts of octane in the fuel, octane is added to petrol to increase its compressibility before itself ignites, we want spark plug to do that."

Over-advanced ignition timing also causes knock.

"I don’t agree, the main reason for plugs to have a heat range is to keep um clean. When a plug runs at the “correct temperature” is far less prone to fouling, go to hot it can result in pre-ignition but if your plugs are fouling up, going up one on the heat range is advisable, misfiring is not good for engines."

Not sure what you "don't agree" on. The optimum center electrode temperature range is from 450 to 800 degrees C. Colder than 450 causes fouling - hotter than 800 risks pre-ignition. Most motorcycle manufacturers allow for one heat range colder or hotter to address cold fouling or high speed operation. Going outside that "recommended" range will cause problems under certain operating conditions.

"Err kind of agree, as I was told, there are two parts to the electrode, one which is made from steel. Steel conducts electricity and is magnetic but is it gets too red hot it becomes austenitic, doesn’t like to conduct electricity and becomes nonmagnetic so becomes more an insulator. This is safety for your engine because it will promote a miss and cool the motor down."

Nothing is designed into the spark plug to "promote a miss". Misfiring is not good - like you said. Has absolutely nothing to do with magnetism or becoming "austenitic" or anything like that. The center and side electrodes are a nickel alloy and usually have a copper core. The copper is for increased heat transfer for better durability. No iron or steel electrodes.

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Old 12-19-2011, 10:01 AM   #28
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Quote:
Originally Posted by V-rider View Post

Nothing is designed into the spark plug to "promote a miss". Misfiring is not good - like you said. Has absolutely nothing to do with magnetism or becoming "austenitic" or anything like that. The center and side electrodes are a nickel alloy and usually have a copper core. The copper is for increased heat transfer for better durability. No iron or steel electrodes.

What I heard from an auto mechanical engineer, the body of the plug is steel including the ground leg, as steel reaches red hot it becomes more an insulator rather than a conductor.

At atmospheric pressure the spark would just jump to any ground if the leg was missing as the coil discharged. But air is a very good insulator being 78% inert nitrogen, when compressed at 8 to 10 times atmospheric pressure in a combustion chamber it’s even harder for the spark to jump and it won’t make the distance to the plug barrel, hence the leg.
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Old 12-19-2011, 12:40 PM   #29
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A little more...

Quote:
Originally Posted by charlie264 View Post
What I heard from an auto mechanical engineer, the body of the plug is steel including the ground leg, as steel reaches red hot it becomes more an insulator rather than a conductor.

At atmospheric pressure the spark would just jump to any ground if the leg was missing as the coil discharged. But air is a very good insulator being 78% inert nitrogen, when compressed at 8 to 10 times atmospheric pressure in a combustion chamber it’s even harder for the spark to jump and it won’t make the distance to the plug barrel, hence the leg.
Nope. The side electrode is a different material - nickel alloy - that is welded onto the shell.

We have done many tests with the side electrode cut totally off - spark jumps fine to the plug shell. Have you ever head of semi-surface discharge plugs? Racing plugs? The spark is jumping to the shell.

Also, think about when your plug gets fouled - where does the spark go? It runs down the side of the carbon covered insulator right to the shell. Plenty of voltage to do so.

Check out the links I posted before. It might clear some stuff up for you. Have a good one.
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Old 12-19-2011, 02:01 PM   #30
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Nope. The side electrode is a different material - nickel alloy - that is welded onto the shell.
Did I say he was old school, once upon a time...Get with the times man, just ordered a set of IX iridium’s.
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