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Old 12-08-2008, 12:34 PM   #1
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Default Spark Plugs - Which Do You Use?

Yes, quite a change from the plugs you guys are used to discussing.

Anyway. Spark plugs.

It has been the consensus that one step colder plugs(from stock) are the appropriate plugs to use. So if you have a 90-93 that means 7's, 94-05, 6's.

As far as the type of plug. Since I started reading this forum religiously, it has been the consensus that the regular Copper V-Power NGK plug, which retails for 2 bucks, is the ideal plug for the job. It is cheap, disposable, and most reliable for turbocharged applications because it does not promote pre-ignition.

But that still leaves me wondering. We cant all be using the same plugs, someone is straying from the norm and is experiencing no adverse affects with the platinum and iridium tipped plugs.

So the questions is - What kind of spark plugs do you use? Why? What are your experiences? How often do you change them? Have you used anything other then the plugs now and noticed a difference?
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Old 12-08-2008, 12:41 PM   #2
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I never have used anything but BKR6E and BRK7Es.

2 reasons: Cheap as hell, and IMO, no better material than copper.


Y8s likes to bling it up with platinum and spend as much on 1 set as I've ever spent in the 15 years of owning the car.
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Old 12-08-2008, 12:45 PM   #3
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Again... cheap and work well are the key for me.

Plat/Irid plugs might have a longer life span... but they will age and loose efficiency over their life like any other plug.

I'd prefer to change my plugs ALOT more often... I think on average its about a 4:1 price ratio of copper to plat/irid... sometimes even more.

Plus it gets you 'into' the motor and plugs can tell you a good deal about overall engine health... so you are adding to the possibility of finding problems early.

<-- will never use anything but ngk bkr7e
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Old 12-08-2008, 12:51 PM   #4
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i use whatever it is FM sells, i can't remember what they are but i haven't even taken a plug out since i've been turbo about 6 years or something like that
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Old 12-08-2008, 12:54 PM   #5
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Originally Posted by Mach929 View Post
i use whatever it is FM sells, i can't remember what they are but i haven't even taken a plug out since i've been turbo about 6 years or something like that
6yrs on same plugs? Ewww....
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Old 12-08-2008, 01:01 PM   #6
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The biggest factor you want is a spark plug that will provide a powerful spark, retain the tip and shed heat.

Iridium has more than twice the melting point of copper (2400C vs 1080C).

However, the way I understand it is this....while both tips aren't going melt inside the chamber, they do retain tons of heat. When the next compression stroke begins, there's a chance you can pre-ignite the mixture simply from a tip being too hot.

Therefore, you want a tip that will conduct heat away from it. Copper is one of the best thermal conductor on earth. It's thermal conductivity is almost 4x greater than iridiums. This ensures the tip cools as fast as possible between strokes, instead of retaining and increasing in temperature.

Copper plugs are about $4 a set.



Now with that said, it's also said that an Iriduim tip is smaller (better smaller sharper point) about 10% the volume. So it is about 25% the mass of the copper tip in the spark plug. With 1/3 the thermal capacity (130/385 in J/(kg-k)) and 25% the volume has about 1/12 the heat retension. It gets hot and makes a hot spark but should cool about 12 times faster than Copper.

Iriduim plugs are about $30 a set.
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Old 12-08-2008, 01:23 PM   #7
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Quote:
Originally Posted by Saml01 View Post

It has been the consensus that one step colder plugs(from stock) are the appropriate plugs to use. So if you have a 90-93 that means 7's, 94-05, 6's.

But that still leaves me wondering. We cant all be using the same plugs, someone is straying from the norm and is experiencing no adverse affects with the platinum and iridium tipped plugs.

So the questions is - What kind of spark plugs do you use? Why? What are your experiences? How often do you change them? Have you used anything other then the plugs now and noticed a difference?
I'm using BRK7Es with no adverse effects and love them. BTW, my car is a 96.
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Old 12-08-2008, 01:28 PM   #8
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dude I bling it up with iridium, not platinum.

there's some discussion about the tiny 0.6mm iridium tip has a higher current density and is easier to spark--especially after many miles. the sharp point plus low wear rate = lots of miles in a motor before replacement.

oh and you can always pull and inspect spark plugs before they go bad. no need to use an inferior plug to force you to do it
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Old 12-08-2008, 01:43 PM   #9
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Just for kicks, I decided to test the limits of how cold a plug you can run in a daily-driven Miata. About a year ago I installed a set of IFR8H plugs (yes, they were expensive). Initially they were gapped at about .025", now they're at .040" with the COPs. After a year of mixed-use driving (mostly city, some highway, some AutoX / canyon carving) they look just fine. No excessive fouling, no degradation to the electrodes.

Unless someone can dyno-prove that running plugs that are "too cold" signifigantly reduces performance or has some other negative impact on the engine, I see no reason not to run the coldest plugs you can get your hands on. Just a little added insurance.
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Old 12-08-2008, 01:45 PM   #10
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Quote:
Originally Posted by Joe Perez View Post
Just for kicks, I decided to test the limits of how cold a plug you can run in a daily-driven Miata. About a year ago I installed a set of IFR8H plugs (yes, they were expensive). Initially they were gapped at about .025", now they're at .040" with the COPs. After a year of mixed-use driving (mostly city, some highway, some AutoX / canyon carving) they look just fine. No excessive fouling, no degradation to the electrodes.

Unless someone can dyno-prove that running plugs that are "too cold" signifigantly reduces performance or has some other negative impact on the engine, I see no reason not to run the coldest plugs you can get your hands on. Just a little added insurance.
Wasn't the issue people would complain about with running a "too cold" plug was it fouling up or something? It seems to be all I can remember about the typical internet mumbo jumbo passed around.
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Old 12-08-2008, 01:49 PM   #11
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Yeah, I thought too cold promotes excess carbon build up. I'm using the 7's. They work, they're cheap, end of story.
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Old 12-08-2008, 01:56 PM   #12
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the heat range is solely the amount of heat the plug can remove from the chamber (one of the more important jobs of the plug)

Quote:
A spark plug's heat range has no relationship to the actual voltage transferred through the spark plug. Rather, the heat range is a measure of the spark plug's ability to remove heat from the combustion chamber. The heat range measurement is determined by several factors; the length of the ceramic center insulator nose and its' ability to absorb and transfer combustion heat, the material composition of the insulator and center electrode material.

Heat rating and heat flow path of NGK Spark Plugs



The insulator nose length is the distance from the firing tip of the insulator to the point where insulator meets the metal shell. Since the insulator tip is the hottest part of the spark plug, the tip temperature is a primary factor in pre-ignition and fouling. Whether the spark plugs are fitted in a lawnmower, boat, or a race car, the spark plug tip temperature must remain between 500C-850C. If the tip temperature is lower than 500C, the insulator area surrounding the center electrode will not be hot enough to burn off carbon and combustion chamber deposits. These accumulated deposits can result in spark plug fouling leading to misfire. If the tip temperature is higher than 850C the spark plug will overheat which may cause the ceramic around the center electrode to blister and the electrodes to melt. This may lead to pre-ignition/detonation and expensive engine damage. In identical spark plug types, the difference from one heat range to the next is the ability to remove approximately 70C to 100C from the combustion chamber. A projected style spark plug firing tip temperature is increased by 10C to 20C.
I would be trying to run the hottest plug you can get away with. If you can get away with it, no reason to dump all the heat directly into the cooling system. Hell, even with boost, my intake temps are lower than they would be stock...I should go back to BKR6Es.
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Old 12-08-2008, 01:59 PM   #13
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IIRC plugs that are too cold pull excessive heat out of the chamber, increase the cooling system load as mentioned above, and slightly decrease combustion efficiency. Plus there is the potential fouling issue. Other than that I see no reason why not to use a cold plug.

FWIW I am using the Iridiums.
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Old 12-08-2008, 02:02 PM   #14
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Quote:
Originally Posted by ZX-Tex View Post
IIRC plugs that are too cold pull excessive heat out of the chamber and thus slightly decrease efficiency.
yeah but remember where that heat goes....I'd rather have a chamber that is hotter to the point of not worrying about detonation or pre-ignition than overloading the coolant system and possibly fouling plugs.
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Old 12-08-2008, 02:14 PM   #15
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I ran 7s for a while, then the store didn't have a full set of 7s when I NEEDED a set so I got some 6s instead. Kept an eye on the knock sensors, nothing's amiss.
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Old 12-08-2008, 02:43 PM   #16
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Quote:
Originally Posted by ZX-Tex View Post
IIRC plugs that are too cold pull excessive heat out of the chamber, increase the cooling system load as mentioned above, and slightly decrease combustion efficiency. Plus there is the potential fouling issue. Other than that I see no reason why not to use a cold plug.

FWIW I am using the Iridiums.
I think saying that colder sparkplugs increase cooling load is a joke. Yeah, on some fine level that's true. But lets be serious. Puting a coat of paint on the block will cause more heat to go into the cooling system than running colder plugs. I wouldn't 'worry' about the cooling system, and run hotter plugs.

This is a simple topic. Too hot, preignition. Too cold, they can fowl out. Find a happy medium. I run 7E's and I'm N/A. They don't stay that clean. But I keep them changed.
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Old 12-08-2008, 02:57 PM   #17
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Quote:
Originally Posted by Braineack View Post
yeah but remember where that heat goes....I'd rather have a chamber that is hotter to the point of not worrying about detonation or pre-ignition than overloading the coolant system and possibly fouling plugs.
Man I have to be more explicit with my responses here, or caveat the implicit ones. People assume you are a dumb ***. Yes I know where the heat goes.

And I agree, detonation is the greater evil, and thus being on the cold side is better.
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Old 12-08-2008, 03:01 PM   #18
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Quote:
Originally Posted by patsmx5 View Post
I think saying that colder sparkplugs increase cooling load is a joke. Yeah, on some fine level that's true. But lets be serious. Puting a coat of paint on the block will cause more heat to go into the cooling system than running colder plugs. I wouldn't 'worry' about the cooling system, and run hotter plugs.

This is a simple topic. Too hot, preignition. Too cold, they can fowl out. Find a happy medium. I run 7E's and I'm N/A. They don't stay that clean. But I keep them changed.
More explicitness required... I did not say that the additional load was necessarily a problem, only that it is there. So, going cooler is OK, but going ridiculously cooler is pointless, and may have undesirable side effects. Its just like anything else, a variable that needs to be tuned for the desired effect.
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Old 12-08-2008, 03:45 PM   #19
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Can fouled plugs be cleaned with a wire brush if the electrode and tip looks good?
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Old 12-08-2008, 03:57 PM   #20
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You can clean them. I used to hit them with a lighter and clean them off with brake clean back when my 2 stroke snowmobile would foul plugs from not being run hard enough.
I don't suggest it though, new plugs are less than $2 a piece and work better.
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