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Old 04-07-2019, 08:03 PM   #1
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Changing Type of Spark Plug Lower Engine Temp?

I've always used Bosch FGR-6-KQE spark plugs. I decided to try some NGK 94279 FR6AHX-S Ruthenium HX plugs because of people always commenting on the Bosch plugs having a prong break off on them, although I have not had that issue, but I thought I would ease my mind on it and go with the NKG plugs.

Plus with the mods done to my car and not knowing if the engine is running lean or rich (she eats a lot of gas though) along with NGK's claims on this plug, I figured why not try them out. I also only run Ethanol-free gas in my car.

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NGK Ruthenium HX is designed for newer engines which demand high ignitability. Double Fine Electrode (DFE) design promotes spark energy concentration and ignites a wider range of air-fuel ratios, offering improved performance in rich or lean engine conditions.
With the Bosch plugs my cars temp gauge was always around 185° to 186°, even during the winter time. Last week I changed to the NGK plugs. I have gone for many drives since installing them, some pretty spirited and just normal driving and my temp gauge just barley cracks past the 180° mark now.

Is it possible that the type of plug you use can affect the engine temp like this?
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Old 04-08-2019, 02:01 AM   #2
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Originally Posted by KRAM36 View Post
I've always used Bosch FGR-6-KQE spark plugs. I decided to try some NGK 94279 FR6AHX-S Ruthenium HX plugs because of people always commenting on the Bosch plugs having a prong break off on them, although I have not had that issue, but I thought I would ease my mind on it and go with the NKG plugs.

Plus with the mods done to my car and not knowing if the engine is running lean or rich (she eats a lot of gas though) along with NGK's claims on this plug, I figured why not try them out. I also only run Ethanol-free gas in my car.



With the Bosch plugs my cars temp gauge was always around 185° to 186°, even during the winter time. Last week I changed to the NGK plugs. I have gone for many drives since installing them, some pretty spirited and just normal driving and my temp gauge just barley cracks past the 180° mark now.

Is it possible that the type of plug you use can affect the engine temp like this?
Heat range of spark plugs refers to the rate at which the firing tip of the plug transfers heat to the cooling jacket of the cylinder head. "Cooler" plugs transfer it faster, "hot" plugs transfer it slower. This keeps the spark plug temperature high, which allows the plug to self clean and prevent fouling.

The heat range of a given plug should have little to no impact on the car's stead state coolant temperature, that is controlled by the thermostat.
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Old 04-08-2019, 06:31 AM   #3
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Originally Posted by JFP in PA View Post
Heat range of spark plugs refers to the rate at which the firing tip of the plug transfers heat to the cooling jacket of the cylinder head. "Cooler" plugs transfer it faster, "hot" plugs transfer it slower. This keeps the spark plug temperature high, which allows the plug to self clean and prevent fouling.

The heat range of a given plug should have little to no impact on the car's stead state coolant temperature, that is controlled by the thermostat.
Yes, I understand the heat range of spark plugs. That's why I didn't mention the heat range in my post, but thanks for the info. The difference is in the plug's design, the Bosch plugs have 4 prongs and the NGK has only one prong and the electrode is made of different material at the tip.

Maybe my NGK plugs made a deal with my thermostat? j/k

Or maybe the thermostat has given up and is sticking open all the time now, just happened at the same time I decided to change my plugs?

I really want to get to the bottom of this, as it's much warmer outside now and my car is running cooler since the plug change. I DD my Boxster, even during the winter it would hit 185° on the highway.
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Old 04-08-2019, 07:37 AM   #4
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Whatever the heat range of your spark plugs, they have no affect on the water temperature of your engine.
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Old 04-08-2019, 10:10 AM   #5
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Whatever the heat range of your spark plugs, they have no affect on the water temperature of your engine.
Why is the heat range even being mentioned? Both plugs have the same heat range. It's the physical difference in the plugs that I am referring to.

Now, from what I feel, the engine is running smoother. It appears to me that the NKG plugs are doing a better job at igniting the air/fuel mixture and doing it at a more proper time. This is allowing a more complete burn and the timing at which it's doing it at is allowing the more of the combustion to escape the cylinder when the exhaust valve open, which allows more heat to escape the engine.

We are not talking a huge difference here, probably around 4° cooler.

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Old 04-08-2019, 12:04 PM   #6
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placebo...
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Old 04-08-2019, 12:15 PM   #7
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Originally Posted by Quadcammer View Post
placebo...
^^ +1

Zero science to support a lower water temp by changing to NGK plugs.
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Old 04-08-2019, 12:33 PM   #8
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Originally Posted by Quadcammer View Post
placebo...
Placebo makes my engine run cooler? Interesting, then human brain has some amazing powers.
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Old 04-08-2019, 12:39 PM   #9
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^^ +1

Zero science to support a lower water temp by changing to NGK plugs.
Pretty sure I laid out some science on why this could be the case, but go ahead and ignore it. Maybe you could have offered information that rebutted it.
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Old 04-08-2019, 01:36 PM   #10
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Pretty sure I laid out some science on why this could be the case, but go ahead and ignore it. Maybe you could have offered information that rebutted it.
+1



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Old 04-08-2019, 02:30 PM   #11
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Pretty sure I laid out some science on why this could be the case, but go ahead and ignore it. Maybe you could have offered information that rebutted it.
If changing the spark plug resulted in more efficiently burning the fuel/air charge, it would generate more heat, not less...………...
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Old 04-08-2019, 02:38 PM   #12
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Originally Posted by JFP in PA View Post
If changing the spark plug resulted in more efficiently burning the fuel/air charge, it would generate more heat, not less...………...
Not if they ignited at the improper time or should I say a more optimal time. Plus a cleaner full burn would allow the combustion to escape the cylinder more efficiently, thus allowing the heat to escape more efficiently.
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Old 04-08-2019, 02:45 PM   #13
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uh no. The type of plug is not changing the timing of the spark. Whatever you're quoting is marketing wank. Not to mention, a modern fuel injected car like the 986 very accurately controls the a/f ratio, so this WIDE RANGE would be between about 12.8 and 14.7, which pretty much any plain jane copper plug can ignite all day for 40k miles, especially at our given compression ratio.

Lets start with how are you measuring these temperatures so accurately?
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Old 04-08-2019, 02:54 PM   #14
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Originally Posted by Quadcammer View Post
uh no. The type of plug is not changing the timing of the spark. Whatever you're quoting is marketing wank. Not to mention, a modern fuel injected car like the 986 very accurately controls the a/f ratio, so this WIDE RANGE would be between about 12.8 and 14.7, which pretty much any plain jane copper plug can ignite all day for 40k miles, especially at our given compression ratio.

Lets start with how are you measuring these temperatures so accurately?
Oh yes the spark can happen faster and with more intensity depending on the what the spark plug is made out of. Have you never watched any videos of different spark plugs sparking? I thought this was pretty common knowledge for gear heads. Go watch some videos on the 4 prong type plugs, they seems to have some latency in their sparking action to them.

If you read my first post, you would know how the measurement was done. By the gauge in the cluster. Now if I had know this was going to happen, I would have logged the temps with my Durametric, it just turned out to be a unexpected surprise.
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Old 04-08-2019, 04:39 PM   #15
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The problem is that there are far too many other variables that you can't keep constant in order to say that the spark plug change was the cause for such a small change in temp as shown on the gauge cluster. Even if you had Durametric data, there are still far too many variables in play.

That is why people are saying "placebo" - they don't mean that you're not seeing a difference on the temp gauge, instead they are saying that it is highly likely NOT the spark plugs and much more likely one or more other variables that can affect the reported coolant temp.
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Old 04-08-2019, 05:23 PM   #16
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The problem is that there are far too many other variables that you can't keep constant in order to say that the spark plug change was the cause for such a small change in temp as shown on the gauge cluster. Even if you had Durametric data, there are still far too many variables in play.

That is why people are saying "placebo" - they don't mean that you're not seeing a difference on the temp gauge, instead they are saying that it is highly likely NOT the spark plugs and much more likely one or more other variables that can affect the reported coolant temp.
What other variables could be involved? I changed the plugs, the temp went down slightly, yet it's much warmer outside now.

Did my thermostat decide to stick open or partially open at the same time I changed my plugs?

I've been thinking about getting one of those lower temp thermostats for years. I've heard pros and cons of running the lower temp stat. I'm not even going to think about it now that my car is at the temp where it should be at.

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Old 04-08-2019, 07:50 PM   #17
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Old 04-08-2019, 08:31 PM   #18
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What other variables could be involved? I changed the plugs, the temp went down slightly, yet it's much warmer outside now.
You're kidding, right? You can't imagine any other variables? Yet you mention one in the following sentence.
How about barometric pressure change? How about where you bought your fuel? (And where THEY bought it? )
How about your fan running more, 'cuz it's hotter outside?
How about relative humidity change?
I can think of dozens of variables, if you want me to continue?


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Old 04-08-2019, 09:07 PM   #19
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What other variables could be involved?
Ok, here's twelve to get us started...

Air temp
Humidity
Pressure
Percentage of cloud cover
Throttle position over the past 5-30 minutes
Load over the past 5-30 mins
Length of time at idle over the past 5-30 mins
Length of time at various speeds over the past 5-30 mins
Fans cycling on or off
Inaccuracy of the temp sending unit
Inaccuracy/inconsistency of visually sighting the temp gauge
Amount of other traffic
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Old 04-08-2019, 09:13 PM   #20
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Oh yes the spark can happen faster and with more intensity depending on the what the spark plug is made out of. Have you never watched any videos of different spark plugs sparking? I thought this was pretty common knowledge for gear heads. Go watch some videos on the 4 prong type plugs, they seems to have some latency in their sparking action to them.
How old are you?
Waaaay bank in the old days, when we used to have to tune ignition curves with weights and springs, it was important to monitor your flame front; ie, get it moving faster. We'd also maximize the quench area for this very same reason. This was particularly important when cylinder pressures were very high (boosted) or when RPM's were very high (10k rpm and up). So yes, in those days, knowing your spark plugs really well was vital. But only in those very extreme situations.

With today's adaptable/ learning ECU's controlling spark and fuel, based on actual readings from sensors means that you can pretty much slap any old plug in there and you'll see negligible differences, other than longevity of the plug itself. (Again, until you start taking about the extremes)

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