Iridium Spark Plugs

[pinholenz]

According to NGK the recommended iridium replacement for our standard D8EA plugs is the DR8EIX.
However, cvincer mentions the DR9EIX as a replacement for the D8EA on the Parts and Upgrades list. Is this a typo or is the cooler DR9EIX plug better suited to our needs?

[Jimustanguitar]

The D9 is one step colder than a D8... There are a lot of folks that will advise you to go down a notch when switching to iridium plugs, but I don't know why this is. It seems to me that a heat rating is a heat rating... Perhaps they truly work better and change the combustion behavior enough that an adjustment is warranted?

There's a lot of google reading on this matter, but I don't have any experience with this on the Vision. I'm curious now too though, so hopefully somebody can enlighten us both :)

[zore]

I'm just curious as to why you would want to put iridium over platinum.  I'm not sure there is any performance increase, only mileage and the platinum are already good to 60k miles.  I've not seen any concrete evidence that there is any performance increase even over the standard plug, they just last longer.  I'm not trying to tell you not to do it, I'm simply asking for my own benefit as maybe I'm missing something.

[Jimustanguitar]

Apparently, iridium allows for a smaller more concentrated spark. http://www.automedia.com/Iridium_Spark_Plugs/pht20010101ds/1

Plus, they're made out of meteors, and that's just bad ass :)


***edit***  I don't think they'll add 750bhp to a Vision like the article says :) Still an interesting read about some of the factors involved though.

[Lucky]

I put I ngk radium plugs in tourer several years ago, they were on sale. Tourer has always been harder to start than any of my other bikes, much more cold blooded. The plugs (and an AGM battery later) made the most difference.

Wires, plug caps, battery cables, new fuse box and wire connector cleaning all seemed to help a little bit, but not as much as plugs and battery.

Carbs and charging system changes didn't help at all.

I did a valve adjustment as a novice and  figured I probably could have done a better job, so I should do it again now that I have done several, but I just haven't bitten the bullet and gotten it done. I think that'll make a big difference. Sorry 'bout the hijack, lol


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[Rikugun]

With conventional plugs it's unlikely you or the engine will notice a one heat range shift up or down.  I'm not sure if this applies to iridium plugs as well but I'd be apt to use the recommended replacement number.

I'm more curious about the resistor. As originally supplied, electronic noise suppression is handled by the cap so non resistor plugs are used. Are there non resistor iridium plugs available and if so any opinions on why they may or may not be desirable?

[The Prophet of Doom]

All iridiums (from NGK at least) are resistor, but they say they are OK to run with resistor caps, and they go brilliantly on my bike.  Biggest improvement I ever made.

[zore]

Sorry for the double post, but it's topical

Taken from carsdirect.com   

http://www.carsdirect.com/car-repair/copper-spark-plugs-vs-iridium-and-platinum-understand-for-top-performance

Copper Spark Plugs

Copper spark plugs are generally considered to have the best performance of any spark plug type. This is potentially different from what advertising companies suggest, but the other metals are, unfortunately, not as conductive in general as copper is. Platinum and iridium plugs are more likely to overheat, which causes damage to the plug components and can compromise the delivery of the spark to the engine block.
Platinum and Iridium Plugs

Platinum and Iridium plugs perform at a lower level than copper spark plugs, because they are less conductive and they tend to overheat. However, the overall longevity of these two types of metal is better than copper plugs. In reality, copper has the best performance of all three and the worst longevity. Platinum has good longevity and the worst performance. Iridium has good longevity and a performance that is decent, which is why iridium plugs tend to be more expensive than any other type. Still, the difference between these plugs in terms of overall quality is minimal, as there is a trade off for each.

Most copper plugs need to be changed every 20,000 miles or so. Platinum and iridium plugs can often go for twice that before they require changing, but the overall performance will not be as good and you may have to deal with overheating of the plugs. This is potentially not worth the added cost of both platinum and iridium spark plugs, although the decision will depend upon your preference.
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Update:

I have been doing a bunch more research and I think my conclusion is that it's situational.  One theme that I'm reading alot of is that you should cap an iridium plug wider than the stock copper unit.  I found dyno results that showed a harley getting 3hp increase with iridiums over stock.  Unfortunately, I'm not sure what stock was.  I'm concluding that your mileage may vary.  I personally noticed no difference in the XZ or my monster.

[Jimustanguitar]

Obviously all 4 types of plugs work. There's a lot of opinion and marketing and misinformation about which is best. They all have pros and cons, so there isn't a single right answer. Do you want the cheapest option because you replace them constantly, do you want the longest service life, are you looking for the highest energy spark, fuel economy, acceleration, etc?

I think it's always going to be a case by case decision. For me, considering our starting problems, carb tuning confusion, and difficulty replacing the front plug, a plug with an intense/concentrated spark, long service life, and tendency to not foul would be important. I haven't tried any of the different options, but on paper I think I'd still choose the iridium ones. Copper is a better conductor, but I wouldn't want to have them foul or need to be replaced constantly.

Has anybody done a comparison on the Vision that has an opinion based on experience? Obviously the iridium plugs are well received, but has anybody tried platinum or copper as well?

[zore]

Other than my weed eater or my 2 stroke snow thrower, I've never fouled a plug.  Properly tuned and running 4 stroke should not foul plugs.

The theory on copper being a better conductor is moot because they are resistor plugs so that kind of throws that out the window.   Better fuel mileage and starting I can't comment on because, while I do run Iridium in all my vehicles, I have not noticed any improvements with regard to mileage or starting.   It is extremely difficult to separate the fact from complete fiction.  The car seems to make sense to me given they last longer, but the bikes I'm not sold on yet. 

[pinholenz]

Agreed, copper conductivity is a not a benefit if there is a resistor in place in the plug. Kind of negates the value of the copper core if its chopped by a resistor. My totally failed plug was an NGK with a resistor. I will replace these with D8EA's without resistors but I can still feel righteous (and not annoy my neighbours) because of the new resistor caps I have just installed.

I believe that all Iridiums come with a resistor.

The info from Zore claims that the Iridiums run hotter  than copper which supports Jim's observation that moving to a slightly cooler D9 Iridium may have some merit. But it begs the question as to why a hotter plug is not rated as such in the first place?

Digging around the Forum I found this thread from nearly 7 years ago when Iridium appeared on the market. Its worth a read as well.

http://ridersofvision.net/rovforum/index.php?topic=4206.msg34208#msg34208

[Jimustanguitar]

So are the folks using iridium plugs on this forum installing a non-resistor cap, or do you have resistor caps and resistor plugs?

Roro has it doubled up, does anybody else run theirs differently?

[Night Vision]

I wouldn't run resistor caps AND (non er id ee um) resistor plugs.... I've seen a no start situation when the two are doubled up

[fret not]

Re the copper core issue, it is used mainly for heat dissipation.

[The Prophet of Doom]

When I fitted my iridiums, I was prepared to invest in non resistor caps, but it wasn't a problem at all.

[Lucky]

I run the ngk iradium plugs and ngk caps. No problems over the last 5-6 years


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[pinholenz]

It looks like NGK have two recommendations for XZ 550 iridium plugs, depending on which side of the Atlantic you live.

At this UK site, they quote the DR8ES (Copper) as standard and recommend the  DR9EVX as a Platinum equivalent and the DR9EIX as the Iridium equivalent. http://www.ngkpartfinder.co.uk/mc_extra.php?id=2897

However on the US site they recommend the DR8EA as standard and the DR8EIX as the Iridium replacement. http://www.ngksparkplugs.com/part_finder/motorcycles/

I haven't found a definitive answer as to the differeence between the DR8ES and DR8EA. One quote said that the DR8ES was half a heat range cooler than the DR8EA. Therefore the cooler DR9EIX iridium replacement  for this makes sense.

It seems some riders like a warmer plug (8's) in cold weather to aid coming up to temperature more quickly and then they run 9's during the summer. Sounds a bit odd.

I think the bottom line is that either the Iridium DR8EIX or the DR9EIX should be OK with the XZ.

[Rikugun]

I haven't found a definitive answer as to the differeence between the DR8ES and DR8EA. One quote said that the DR8ES was half a heat range cooler than the DR8EA. Therefore the cooler DR9EIX iridium replacement  for this makes sense.

Found this on a SOHC 4 Honda site...  "The D8ES was a "Super-wide heat range" sparkplug. The EPA made NGK discontinue these in the early 1990s. Their replacement was the D8EA, a colder plug by about 1/4 heat range step."    and somewhat related...  "The D8ES-L (now defunct, except in the resistor version DR8ES-L) has a Longer tip (i.e., Extended Tip) to help burn off deposits."