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Spark Plug Gap, looking for personal experiences.

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Old 03-18-2015, 06:15 PM
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Spark Plug Gap, looking for personal experiences.

I know what Mazda recommends, I know what NGK, and I've seen what a few people say they use on turbo or FI setups. What I would really like to hear are everyone's personal experience with different gaps. What gaps have everyone, for the most part, been the most comfortable with?

Searched quite awhile and couldn't find a thread close that dealt with just this subject without being a part of something else somewhat related where gaps were only passing mentions or the Mazda/NGK recommendation were quoted.
Old 03-18-2015, 06:29 PM
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So you just want to make the same s****d mistake as someone else who had no idea what they were doing rather than buy the proper pre-gapped plugs?
Old 03-18-2015, 06:50 PM
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No threads because its a non-issue. Only if there were varying opinions would there be multiple threads.

Just buy OEM NGK plugs, don't mess with the gap, install, be satisfied that the work correctly and ideally.

Posted From RX8Club.com Android App
Old 03-18-2015, 07:07 PM
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Speaking of plugs, I just bought my yearly set of NGKs for $63 shipped this morning. They will go in this weekend with the gap unmolested.
Old 03-18-2015, 08:59 PM
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Originally Posted by TeamRX8
So you just want to make the same s****d mistake as someone else who had no idea what they were doing rather than buy the proper pre-gapped plugs?
From NGK:
3. Gapping

Since the gap size has a direct affect on the spark plug's tip temperature
and on the voltage necessary to ionize (light) the air/fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability
in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need.

A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximizes burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.

With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think.
Yeah, some mistake I'm making. There was also a quote from someone who was told by NGK their plugs did NOT come pre-gapped and I'm seeing other sources say they are, hence my concern. Also, even if spark plugs you bought claimed to be pre-gapped, who wouldn't take the 10sec and check them, or adjust them to their PREFERRED gap? Is it really that much trouble to ask what people generally prefer for their gaps, and if they have generally seen NGK pregapped correctly. I've measured mine already, of course.....

Appreciate your awesome input.

Last edited by Sphere; 03-18-2015 at 09:16 PM.
Old 03-18-2015, 09:00 PM
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Originally Posted by stvnscott
Speaking of plugs, I just bought my yearly set of NGKs for $63 shipped this morning. They will go in this weekend with the gap unmolested.
Same, got mine for $65 total.
Old 03-18-2015, 09:06 PM
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Originally Posted by RIWWP
No threads because its a non-issue. Only if there were varying opinions would there be multiple threads.

Just buy OEM NGK plugs, don't mess with the gap, install, be satisfied that the work correctly and ideally.

Posted From RX8Club.com Android App

Everything I have read (including from NGK) has given varying preferences for gaps. I have OCD. I didn't think asking a simple "Hey, what have you found to be the best performing gap on your plugs in a NA Rx8?" would cause much condescending attitudes when it seems to be a rather straight forward inquiry.

Like I said, I have OCD, especially about my 8, so I tend to go overboard when checking, rechecking, and double checking. And I've seen multiple varying numbers from Mazda, NGK, other owners....
Old 03-19-2015, 05:24 AM
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Originally Posted by Sphere
Everything I have read (including from NGK) has given varying preferences for gaps. I have OCD. I didn't think asking a simple "Hey, what have you found to be the best performing gap on your plugs in a NA Rx8?" would cause much condescending attitudes when it seems to be a rather straight forward inquiry.

Like I said, I have OCD, especially about my 8, so I tend to go overboard when checking, rechecking, and double checking. And I've seen multiple varying numbers from Mazda, NGK, other owners....
i've noticed that generally asking any question here is a waste of time.

people would rather waste their time with a bashing comment or a learn to search comment, than help someone, or even just ignore the god damn post.

im sorry you wasted your time,
Old 03-19-2015, 07:08 AM
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Originally Posted by Sphere
Everything I have read (including from NGK) has given varying preferences for gaps. I have OCD. I didn't think asking a simple "Hey, what have you found to be the best performing gap on your plugs in a NA Rx8?" would cause much condescending attitudes when it seems to be a rather straight forward inquiry. Like I said, I have OCD, especially about my 8, so I tend to go overboard when checking, rechecking, and double checking. And I've seen multiple varying numbers from Mazda, NGK, other owners....
Team rx8 does condescending very well but mostly enjoys belittling better.

Here's a question, did u compare the gaps between the two leading plugs? Were they identicle?
Old 03-19-2015, 07:11 AM
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I always assumed that the new gen plugs we use were gapped but I'm also aware of the "old days old ways" which u would check against factory specs before use. And let's face it, when u clean them at service time and fiddle pulling them out etc, there is always a risk of bumping the gap closed a little hey.
Old 03-19-2015, 08:58 AM
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Originally Posted by Sphere
...would cause much condescending attitudes when it seems to be a rather straight forward inquiry.
What attitude? I certainly didn't have any when I responded.

There is nothing you need to do for the RX-8 NGK plugs. I gap my NGK plugs for my Miata, but I never had to for my RX-8.


If you want further confirmation, see the attached PDF from the dealer documentation.


So basically leave them alone if they are new. If you are checking used plugs, then replace them if the gap has changed. Nothing about changing the gap for new, used, or damaged plugs.


It's not discussed on here because you don't have to do anything with the plugs, and everyone is in general agreement on it. I'm not being condescending, just stating the simple fact of why you don't find discussion about it.

The only stuff that gets major discussion is the stuff that ISN'T agreed on

Last edited by RIWWP; 03-19-2015 at 09:03 AM.
Old 03-19-2015, 05:04 PM
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Originally Posted by Heeroguy
i've noticed that generally asking any question here is a waste of time.

people would rather waste their time with a bashing comment or a learn to search comment, than help someone, or even just ignore the god damn post.

im sorry you wasted your time,
Yeah I've seen it from a number of members, no worries.
Old 03-19-2015, 05:06 PM
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Originally Posted by SiNfidelity
Team rx8 does condescending very well but mostly enjoys belittling better.

Here's a question, did u compare the gaps between the two leading plugs? Were they identicle?
I did compare the gaps. The gaps were identical across all 4, leading and trailing. I have read in a number of threads (on here) that most would go with a wider gap on the trailing. Which was aother reason why I posted this, since they had identical gaps on all 4.
Old 03-19-2015, 05:07 PM
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Originally Posted by Heeroguy
i've noticed that generally asking any question here is a waste of time.

people would rather waste their time with a bashing comment or a learn to search comment, than help someone, or even just ignore the god damn post.

im sorry you wasted your time,



The responses were accurate and helpful. Simple research would have negated the need for this thread in the first place. Thorough research is encouraged.
Old 03-19-2015, 05:11 PM
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Originally Posted by RIWWP
What attitude? I certainly didn't have any when I responded.

There is nothing you need to do for the RX-8 NGK plugs. I gap my NGK plugs for my Miata, but I never had to for my RX-8.


If you want further confirmation, see the attached PDF from the dealer documentation.


So basically leave them alone if they are new. If you are checking used plugs, then replace them if the gap has changed. Nothing about changing the gap for new, used, or damaged plugs.


It's not discussed on here because you don't have to do anything with the plugs, and everyone is in general agreement on it. I'm not being condescending, just stating the simple fact of why you don't find discussion about it.

The only stuff that gets major discussion is the stuff that ISN'T agreed on
I went into posting this thread expecting to get flamed a bit. When I saw Team's post confirming exactly what I expected from some of the members on this forum, I just became more apprehensive towards every other post. I wasn't specifically saying your attitude, I was saying "the attitude" as in, the general shitty attitude (like Team's) that some members on this forum feel they have to put towards others. It wasn't meant as your attitude. I appreciate your response and confirming that you never gapped on your Rx8.

That's really all the more I was looking for was confirmations from others on whether they gapped or didn't need to with NGK. And if they did, what their preference was. OCD is a bitch.
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Old 03-19-2015, 08:01 PM
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Don't take it personally or too seriously. Lots of personalities here. Also lots of good info if you know how to search first and ask later after you haven't found an answer. Take the good bits and leave the bad bits behind
Old 03-19-2015, 08:44 PM
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Originally Posted by 9krpmrx8



The responses were accurate and helpful. Simple research would have negated the need for this thread in the first place. Thorough research is encouraged.
Ironically, when I WAS doing my research, which I quite obviously did, otherwise I wouldn't have the questions I had....I came across this post which isn't very old. It's quite obvious there ARE different recommendations by Mazda and NGK, as well as gaps some others have found to be better.

https://www.rx8club.com/series-i-maj...5/#post3968928

Last edited by Sphere; 03-19-2015 at 08:46 PM.
Old 03-19-2015, 08:45 PM
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Originally Posted by slash128
Don't take it personally or too seriously. Lots of personalities here. Also lots of good info if you know how to search first and ask later after you haven't found an answer. Take the good bits and leave the bad bits behind
Oh I noticed that long before I posted anything. But with any forum there are good posters and trolls.
Old 03-19-2015, 09:41 PM
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I just looked at the boxes my new plugs are in, and the instructions say not to re-gap them. They are precision set from the factory.
Old 03-19-2015, 09:50 PM
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Mine don't say anything about not gapping them, but they do show an image that shows not to gap them with a regular, coin gapper that can damage the iridium point. Maybe that's what you're seeing?
Old 03-20-2015, 07:13 AM
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NGK's website comments are about their plugs in general, and are not model or plug part # specific.

For their piston plugs, yes, you often need to set the gap. I do with my MSM as an example.

You do not for the RX-8.
Old 03-20-2015, 07:25 AM
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now maybe you can understand the intent of the reply, which was not a reflection on the question being asked but rather a direct answer to it ...

hopefully you won't make the same mistake ....
Old 03-20-2015, 07:33 AM
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Originally Posted by Sphere
Mine don't say anything about not gapping them, but they do show an image that shows not to gap them with a regular, coin gapper that can damage the iridium point. Maybe that's what you're seeing?
I kind of doubt NGK's intent with that graphic is to specify which type of gap tool you should not use. Low info wrench monkeys do not look for nuance in infographics. It is much more likely, the graphic means, "Do not re-gap these plugs."

To answer your original question, I have never experimented with spark plug gap in an RX-8, do not intend to, and therefore have no insight for you.
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