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Old 04-27-2012, 10:46 PM   #1
Ralph47
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Default May be a silly spark plug question

So I know my 99 Dakota inside and out, I know what the motor likes and does not. I do not know my subbie yet tho

Is there a plug that is better for my to run on my stock motor? I am running the OEM NGKs at the moment. I know this is probably a silly question but I thought I would ask before I pick up the replacements

Its an 09 Impreza 2.5i with nothing more than a drop in K&N and no plans for the motor in the near future
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Old 04-28-2012, 03:53 AM   #2
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Short answer: Keep using the NGK (although you didn't state which model and just the brand)

What you should have done before making this thread: Search and read the FAQ's. The Spark Plug FAQ was literally a couple threads below yours before I replied to it.

Good luck, have fun.
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Old 04-28-2012, 05:42 AM   #3
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run the stock plugs to 70k miles or so then put the same thing right back in and dont try to 'gap' them....dont put anything between the electrodes at all.....install as supplied
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Old 04-28-2012, 12:57 PM   #4
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Ok that is kinda what I figured, stock motor so the OEM is fine.

They are the platinum NGKs, not sure of the specific model.

Thought I would double check before I replaced them, tho I may hold off even tho the manual says to change them every 35k that seems a little much for platinum plugs....
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Old 04-29-2012, 07:50 AM   #5
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For platinum plugs I would, but that's just me.
Change as often as you like or don't.

But yeah, by model I mean copper, platinum, iridium, etc. "Specific model" as you say I assume you meant I was asking for the part number which would probably be FR5AP-11.

I use BKR5E-11 (copper / V-Power) and change them more often.
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Old 04-29-2012, 10:08 PM   #6
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I did assume the part number lol

As a rule I dislike platinum plugs but being they are OEM I will continue using them :/
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Old 04-30-2012, 01:24 AM   #7
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It's always your choice. Just do what works best for you and your car.
Factor in price, change intervals, performance (mileage/economy, "power"), etc.

If we all stuck with OE then this forum would be quite dead, there would be no aftermarket and we would be hella poor from spending it all at the dealer.
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Old 04-30-2012, 10:09 PM   #8
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lol this is true but my understanding is that platinums are good for like 75k+ and unless the copper plugs will boost my mpg or performance on my stock motor, I will side with the lazy for the time being
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Old 06-05-2012, 06:20 PM   #9
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How would I go about figuring out what copper plugs I need? I wanna change my platinum plugs out soon and I want to swap to coppers but NGK's site only lists the platinum and the iridium plugs

Tho I may look into those too
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Old 06-05-2012, 06:28 PM   #10
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Quote:
Originally Posted by Ralph47 View Post
How would I go about figuring out what copper plugs I need? I wanna change my platinum plugs out soon and I want to swap to coppers but NGK's site only lists the platinum and the iridium plugs

Tho I may look into those too
do an application cross reference search on sparkplugs.com
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Old 06-06-2012, 03:20 PM   #11
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Why anyone would want to put in an inferior spark plug in their car is beyond me. Please, tell me WHY you want to switch to "coppers"?

Last edited by Bacon117; 06-06-2012 at 03:27 PM.
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Old 06-06-2012, 08:24 PM   #12
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Why anyone would want to put in an inferior spark plug in their car is beyond me. Please, tell me WHY you want to switch to "coppers"?
If your not going to explain WHY one shouldnt, then dont worry about it.

I already got new NGK plats in the car waiting to be put in...
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Old 06-06-2012, 08:59 PM   #13
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Quote:
Originally Posted by Bacon117 View Post
Why anyone would want to put in an inferior spark plug in their car is beyond me. Please, tell me WHY you want to switch to "coppers"?
Quote:
Originally Posted by Ralph47 View Post
If your not going to explain WHY one shouldnt, then dont worry about it.

I already got new NGK plats in the car waiting to be put in...
well......if you knew that Bacon117 was a spark plug engineer....yeah, no ****....for NGK....would that sway you???
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Old 06-07-2012, 09:18 AM   #14
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Quote:
Originally Posted by Ralph47 View Post
If your not going to explain WHY one shouldnt, then dont worry about it.

I already got new NGK plats in the car waiting to be put in...
I would be happy to explain actually. I'm just curious as to why you believe they are superior.

A nickel spark plug, commonly called "copper" is inferior to an iridium or pt plug in EVERY measurable way, except price. The term copper is from the 1980's and 1990's when Champion trademarked the name "copper" for their standard nickel spark plugs. I believe back then, copper was NOT used in the first iridium spark plugs, probably to keep price down.

Today, all NGK spark plugs have the same amount of copper in the exact same configuration. I don't know about other makers. I'm 99% sure Denso does, and 70% sure Bosch does. I don't know as much about them, since I don't work there. However, any information I tell you can be used to understand plugs from any manufacturer.

So why copper? A spark plug has to be able to transfer enough heat from the tip so that it doesn't over heat. An over heated spark plug will damage an engine. This can occur at high engine loads. At the same time, a spark plug needs to stay warm enough at cruising speeds so it doesn't collect carbon, and misfire due to carbon fouling. Copper allows us to design the spark plug so that it acts like a hotter spark plug at cruising speeds, but can still handle heat at high load / high speed.

What does copper do for performance? Nothing. Copper only affects the temperature of the tip of the spark plug. The temperature of the center electrode does not affect engine performance at all. Unless it over heats... But that will not happen if you use the heat range that came with your car. Why do so many people believe copper is better? Advertising. Champion did a great job of selling their product 20-30 years ago, and people still believe those claims today.

I'm going to explain ignitability below, which has a lot to do with heat transfer, but over a different time scale. The copper transfers the most heat AFTER the spark happens, while the combustion in the chamber is occurring. Ignitability is heat transfer only just after spark, around 5-10 ms (milliseconds). I just want you to understand that while these are similar phenomenon (heat transfer), they happen on different scales, so one does not affect the other.

Why is iridium or pt superior?
1.) Ignitability: Iridium and PT have much smaller center electrodes. When the coil fires, and the spark occurs in the gap, a small flame kernel is initiated. Again, this is on a VERY small time scale. While this flame kernel is very small, any metal around it will absorb heat. Since the flame kernel is small, any heat absorbed will have an effect as combustion grows through the cylinder. The smaller electrode of an iridium or pt plug help to reduce this heat absorption. The less energy reduced from the flame kernal is more energy that makes it out to the cylinder, for a more complete burn of the fuel.
2.) Wear: This is one is simple. Iridium and Pt are MUCH harder elements than nickel, so they don't wear as easily.


And yes, as Uncle Scotty said, I'm an engineer (A test engineer to be specific), and I work for NGK. I AM the local expert on spark plugs. Don't believe me? Come visit me at the NGK headquarters in MI. Ask for Russell Senior. You can buy me lunch.
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Old 06-08-2012, 10:06 AM   #15
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Quote:
Originally Posted by Ralph47 View Post
If your not going to explain WHY one shouldnt, then dont worry about it.

I already got new NGK plats in the car waiting to be put in...
So really, what information do you have that says standard plugs are superior to Iridium or Platinum? I'm actually curious as to what people have heard. I won't tell you if you are right or wrong, unless you want me to. I just would like to hear what you know.

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Old 06-08-2012, 11:08 AM   #16
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Quote:
Originally Posted by Bacon117 View Post
So really, what information do you have that says standard plugs are superior to Iridium or Platinum? I'm actually curious as to what people have heard. I won't tell you if you are right or wrong, unless you want me to. I just would like to hear what you know.

so slathering anti-seize on coppers don't make them better either?
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Old 06-08-2012, 11:33 AM   #17
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Originally Posted by fastnoypi View Post
so slathering anti-seize on coppers don't make them better either?
Another product of 30 year old technology, lol. Any quality modern spark plug will have plating on the threads that negates the need for anti-seize.
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Old 06-08-2012, 12:09 PM   #18
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Quote:
Originally Posted by Bacon117 View Post
Another product of 30 year old technology, lol. Any quality modern spark plug will have plating on the threads that negates the need for anti-seize.
Even my shop teacher doesn't talk about this.

God I love these forums; getting info from a spark plug pro himself. Thanks!
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Old 06-08-2012, 01:03 PM   #19
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Bacon117, excellent read there bub.

I think you may have scared away the OP however.
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Old 06-08-2012, 02:08 PM   #20
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Bacon117, excellent read there bub.

I think you may have scared away the OP however.
Thanks, Kiddo.

It wasn't mean to be a pissing match to scare him away. There are a lot of people, professional tuners included, that for some reason believe standard plugs ("coppers") are superior. I'm not going to be able to convince the world by myself, but I can at least help educate a few people.
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Old 06-08-2012, 03:57 PM   #21
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^^I remember reading an article by a popular tuner (it was posted here some time aback), about the merits of "copper" plugs, and indexing said plugs.

He maintained that gapping was an absolute necessity, hence the use of coppers, and that indexing was a vital part of optimizing that ignition setup.

Any thoughts on gapping and especially, indexing, for "stage 2" cars and onwards?

(I currently use Iridiums btw).
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Old 06-11-2012, 12:14 AM   #22
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Indexing certainly does have an effect. The effect on port injected engines is fairly small unless the OEM designed the combustion chamber and intake to have poor mixing or they are doing something special with how the air/fuel mixture flows in the cylinder(whether intentionally or otherwise). The engines that benefit from indexing the most are DI engines or 2 stroke engines.
The point of indexing is to point the opening between the Ground Electrode and Center Electrode toward the intake port. The idea is to get the air fuel mixture into the spark gap as best you can. If the ground electrode is blocking the path, it might cause a lean spot in the gap, causing a misfire, or poor combustion.

I've done work with a few OEM's on indexing, and while they all see gains, it's rarely enough justify the cost. (we actually make indexed plugs for some applications, but again it's not cheap). It's a huge pain in the ass to custom index plugs in a vehicle, especially a Subaru (since it's hard to see the plug at all).

Any gains seen by indexing would be completely negated by using a standard plug over an iridium or pt. Also, using an Iridium plug will reduce any gains seen by indexing making it even more unnecessary. For example, let's say a poorly indexed standard plug gives you a combustion rating of 10. Let's say indexing this standard plug improves combustion to a 17. Using an iridium plug will get you to 30, but indexing an iridium plug will only get you to 32 or 33. I made these numbers up for demonstration as NGK is a very secretive company. If I gave you actual data, I would probably lose my job. However, these numbers are similar to our actual data.


Gapping: A vehicles ignition system can only handle a certain max gap size. At some point, the coil simply does not have the capacity to initiate spark at the gap. So, when a vehicle is designed, the engineers determine this max gap size. Now, the bigger the gap, the higher ignitability the plug has. HOWEVER, the bigger the STARTING gap of the plug, the less miles you can drive before the gap grows to the max gap. A balance is struck between performance and durability in this case. So, it is better for performance to run a bigger gap, but you will get less miles out of the plug before you replace it or have to re-gap it.

Determining the max gap size an engine can handle is difficult without special tools, or specific knowledge of the coil. The only way you can really do it on the street is to keep opening the gap until either you reach 1.1mm or the car starts to misfire. Don't go much beyond 1.1mm as the plug may start to side spark, and you will lose these gains. If you have an NA engine you can go up to 1.3mm. If you had the tools, you could probably go beyond the 1.1mm limit. If you have at least an oscilloscope, PM me and I can explain how to do it.

I can't tell you how much gain you will see by doing any of this. I don't look to eek out the last drop of power out of my engine, so I've never tried any of this on the Subaru. I also can't look at the actual engineering data for Subaru since all that goes on in Japan. There will be gains by doing this, but the gains will be small. It would be hard to measure on a chassis dyno. We measure it either using special engines, or actual cylinder pressure data.

Also, it's easy to break the iridium or platinum tip on a spark plug if gapped incorrectly. This is why we recommend to NOT gap iridium or pt plugs. It's not that they cannot be gapped, it's that they are easy to break.


To summarize for those who think tl:dr:
Indexing: Does have an effect, but it is small unless your engine is DI or 2-stroke. Point the gap opening toward the intake port.
Gapping: Bigger is better for power, but bigger = less miles. Also, Iridium and platinum tips are easy to break if gapped incorrectly.

Last edited by Bacon117; 06-11-2012 at 12:52 AM.
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Old 06-11-2012, 02:21 AM   #23
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Bacon117, this would be great if it could be put in a second spark plug stickie. No offence to Unibomber.
Great information!!!
More please!
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Old 06-11-2012, 06:55 AM   #24
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Bacon117, thanks for the answer! So that pretty much sums it up - gains, but miniscule.

Does the "increasing gap with mileage" (I assume due to usage / wear on the plugs' electrodes etc) have a less noted effect with iridium's vs platinum, or vice versa?
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Old 06-11-2012, 08:32 AM   #25
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Originally Posted by Bikelok View Post
Bacon117, this would be great if it could be put in a second spark plug stickie. No offence to Unibomber.
Great information!!!
More please!
Some of it is. I contributed a lot to that sticky, but I can't remember what all is there.
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