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  1. #1
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    NGK RUTHENIUM HX PSPE version. 0.021" gap


    I had the Autolite APP 5682's , about a year old. I took 2 data logs in the morning with the old plugs and 2 in the evening with the new plugs. (NGK 91784 aka LKAR8BHX) The orange and green lines are the new plugs and the blue and red lines are Autolite Double platinums. I didn't accelerate from the same rpm each time so below 4000 rpm you cannot really compare but once the boost stabilized you can see the new plugs made a huge difference. It was 3 cooler but I used SAE correction for temperature.


    It was not missing or having timing corrections on the old plugs.

    Approximate gap 0.021" not dragging on a 0.020" feeler gauge and a 0.022" would not fit.

    This is a custom (Wedge/Ken) E50 tune 22-23 psi stock turbos. FBO except for outlets, no cats. I need to set my shift points up to see where the HP drops off and reset them to what these plugs are doing for HP and TQ at higher rpm's.

    These are Nissan GT-R plugs 2 heat ranges colder than N54 stockers.

    Not sure anyone has tried this particular plug.(that I have seen) I would love to see someone else dyno or virtual dyno before and after with these plugs. Cheaper than Iridium and better power.

    PSPE (projected square platinum electrode) provides the best ignitability and service life for high-heat engines. This NGK-patented design is recommended for turbo and supercharged engines.

    Ruthenium HX Spark Plugs | NGK Spark Plugs
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    +1 rep

    i know one step colder and ethanol is a pretty hard start even with new injectors. Summer has improved the start but I can’t imagine running 2 steps colder when winter hits. I’m not quite to 20 psi and haven’t had any misfires / plug issues. Were you having issues that made you consider the 2 steps colder?

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    The heat range of a spark plug has nothing to do with cold starts. Ethanol just doesn't want to light when it's cold. That's why summer E85 is usually E85 and winter E85 is E70 in my area anyway. One failure to start cold was enough to run a 91 octane gas tune for the winter. The Autolites were 1.5 heat ranges colder. The heat range is the plugs ability to cool itself under high load and resist pre-ignition. They can foul sooner because they don't get hot enough to self clean... A hot plug will have longer thinner porcelain around the center electrode and a colder plug will have shorter thicker porcelain to transfer heat from the electrode to the outer shell to the head.

    The two steps colder were the only Ruthenium option with matching specs to fit N54. I think they had one that was stock heat range but it wasn't PSPE and when I run 23 psi I don't want stock heat range. If a Nissan GT-R can run these without issue, I see no reason an N54 can't. Pretty sure 12.4:1 AFR at 20+ pounds of boost is going to keep them clean...

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    Quote from a Polaris Tuner: I have a lot of people come to me wanting a "hotter" spark plug to get their engine to start better in cold weather. My answer to that "all plugs start out at the same temperature and that is whatever the temperature the engine is".

    The heat range of a spark plug has nothing to do with how "hot" the spark is. This article on the NGK website explains it best:

    One of the most misunderstood aspects of spark plugs is its heat range. It is believed by many that the heat range measures spark temperature or intensity. This is incorrect as the heat range is actually a measurement of the plug’s ability to transfer heat away from the tip of the spark plug. One cannot change the temperature of how hot a fuel burns.

    A hot spark plug has an insulator design that will be slower to draw heat away from the plug tip (thinner insulator mass), whereas a cold plug has an insulator design that will be faster to draw heat away from the plug tip (thicker insulator mass). For a spark plug to function properly it must have a tip temperature hot enough to invoke self-cleaning, while remaining cool enough to avoid pre-ignition.

    For most vehicles, the factory recommended heat range is sufficient; however, on some modified or special-use engines, alternative heat ranges may be necessary.

    Gap on the other hand can affect cold starting but on that I also have little choice as I need 0.020"-0.022" A wider gap can create a hotter spark because the coil has to build a higher voltage to overcome the larger gap. But a larger gap won't make ethanol any easier to light off when cold.


    UNDERSTANDING SPARK PLUG HEAT RANGE

    One of the most misunderstood aspects of spark plugs is its heat range. It is believed by many that the heat range measures spark temperature or intensity. This is incorrect as the heat range is actually a measurement of the plug’s ability to transfer heat away from the tip of the spark plug. One cannot change the temperature of how hot a fuel burns.
    A hot spark plug has an insulator design that will be slower to draw heat away from the plug tip (thinner insulator mass), whereas a cold plug has an insulator design that will be faster to draw heat away from the plug tip (thicker insulator mass). For a spark plug to function properly it must have a tip temperature hot enough to invoke self-cleaning, while remaining cool enough to avoid pre-ignition.

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    What about any concerns about blowout at higher boost?

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    I don't have concerns of blowout with a 0.021" gap and 23 pounds of boost, but if someone needs to gap down to 0.018" to avoid that, this would be the plug to use because of the PSPE design. Spark area is more exposed to the combustion chamber. The PSPE design could be a problem for high horsepower applications (say over 700hp as a guess) I'm not sure about the tiny wire on the ground strap, it might get hot. But NGK thinks it's OK for a spark plug 2 heat ranges colder than an N54 stock spark plug, so assume they don't think it will be an issue.

    In my custom tune I have also disabled multi-spark at idle when engine temp is above 176F and engine still runs smooth with no misfires.

    Testing with these plugs vs. Iridium shows they make more power and when I bought mine they were cheaper than 1 heat range colder Iridiums. They are supposed to last longer too because Ruthenium has less electrode erosion than Iridium.

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    Just to share some more information.

    You can't hurt an engine by running a spark plug with a colder heat range than recommended. You can however damage an engine running a plug with a heat range too hot for your modifications due to pre-ignition of the fuel mixture. The only possible downside would be fouling more easily because they don't get as hot to self clean.

    But since this is the plug used in a Nissan GT-R (presumably without fouling issues) and it's the same heat range that a N55 uses. The only difference being, an N55 plug is a 12 point hex and this plug is a 6 point hex. It could be used in an N55 using an N54 spark plug socket (although most 12 points will work on a six point, but there may be something special about the pattern on the N55 plug, don't know, don't have an N55)

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    Been running these plugs for 2 months. Didnt personally notice any difference. I'm. On full e85 and 30psi 6868

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    Well in my case that was a 2-4% increase in power, your not going to feel that in your butt dyno. That's why I recommend before and after dyno data. That's how I compare all my upgrades. It's how I know Inlets gave me 10hp which I also didn't notice but I saw it in the data. Hp/dollar the plugs did more than the inlets.

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