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What is the best plug to run in a '03 VTX 1800? I just installed the Bosch 4 plug and Im not too impressed with the performance. (could be Im just thinkin that) Any info is appreciated----- :shock:
 

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Me, Tapper, Pete and Johnny Cheese ran the Bosch +4's, NGK's and Uber plugs on the dyno side by side, one after another, same bike, same dyno and all 3 plugs showed less than 1 HP difference between all 3 sets. About 1/2 HP difference really...

Just a bit of info based on facts, I run the 4419's with no problems but everyone is different. :wink:
 

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I've been running 4419's for a while. They've been good plugs. If your heart is set on Iridium plugs you can give NGK BKR5EIX-11 a shot. They are about $7.00 a plug. Beats the hell out of $20.00 for a certain overhyped plug. I've just started running them so I can't tell you anything based on my experience. A friend of mine recommended them and he says they are a good plug. Considering how he rides and how performance conscious he is, that's good enough for me.
 

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Actually, the plugs do make a difference, but mostly at RPMs less than 4000. At peak horsepower, they don't matter quite as much. There are also other effects that play into the decision.
 

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I just put NGK (BKR5EIX-11) 5464 in mine and it runs really good. They're pricey $14.00 each, but seem to be really good.
 

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Iron Cross said:
I just put NGK (BKR5EIX-11) 5464 in mine and it runs really good. They're pricey $14.00 each, but seem to be really good.
Sparkplugs.com... a little less than $7.00 each plus shipping...
 

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Thanks, I'll remember that!!!!!!!!
 

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iCe said:
Iron Cross said:
I just put NGK (BKR5EIX-11) 5464 in mine and it runs really good. They're pricey $14.00 each, but seem to be really good.
Sparkplugs.com... a little less than $7.00 each plus shipping...

DITTO. I paid $11.71 each @ www.sparkplugs.com . Call HDL and let them beat price by 5%
 

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Tapper said:
Actually, the plugs do make a difference, but mostly at RPMs less than 4000. At peak horsepower, they don't matter quite as much. There are also other effects that play into the decision.
Did you include a set of stock plugs in the test?

The electrode on the two different Iridium plugs that I have looked at, NGK and Uber, is not ALL Iridium. In fact, the percentage of Iridium tip compared to the overall length of the center electrode is very low and therefore the conductivity benefits that people talk about are all but nil. It's got a little 1/8th-3/16th inch tit of Iridium welded on the tip. The center electrode is a lot longer than that (for obvious reasons). So I'm not so sure that is what makes them spark better, if they spark better than the stockers. I don't think that anyone has done that test. It wouldn't surprise me if the stock plugs are better than any of them because their tip is pointed which should lead to a better spark. You get the SAME THING as the Ubers in NGK for 1/2 the cost. And like I said, I don't think either are better than the stock plug. Possibly worse from a performance perspective. That's just an opinion though.
 

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iCe said:
Tapper said:
Actually, the plugs do make a difference, but mostly at RPMs less than 4000. At peak horsepower, they don't matter quite as much. There are also other effects that play into the decision.
Did you include a set of stock plugs in the test?

The electrode on the two different Iridium plugs that I have looked at, NGK and Uber, is not ALL Iridium. In fact, the percentage of Iridium tip compared to the overall length of the center electrode is very low and therefore the conductivity benefits that people talk about are all but nil. It's got a little 1/8th-3/16th inch tit of Iridium welded on the tip. The center electrode is a lot longer than that (for obvious reasons). So I'm not so sure that is what makes them spark better, if they spark better than the stockers. I don't think that anyone has done that test. It wouldn't surprise me if the stock plugs are better than any of them because their tip is pointed which should lead to a better spark. You get the SAME THING as the Ubers in NGK for 1/2 the cost. And like I said, I don't think either are better than the stock plug. Possibly worse from a performance perspective. That's just an opinion though.
We did indeed include a stock set of plugs. I worked on finishing up the article last night, I'm almost done. So soon now :)

Actually, the iridium does make a difference. Remember - the iridium is intended to affect the "potential" of the air gap in the plug, not the direct metal to metal contact. Most of these plugs contain a thin wire electrode plated in iridium/rhodium alloy. The Ubers have a welded iridium pad on the tip of the ground, the stockers have a platinum ground tip.

The issue is, that the amount of electricity required to produce a spark, is a function of the potential of the air gap (in volts). The better conductor each end of the gap is, the lower the potential is, and the easier it is to produce a spark there. So, an iridium/iridium gap will spark at a lower voltage than an iridium/platinum, platinum/platinum, etc. Thus, if the potential is lower, and the voltage remains the same, the spark is larger.

We didn't really see the spark size translate into maximum produced horsepower so much, but we did see it translate into peak numbers that were not tied to the head temperature. That is, the Ubers produced max horses whether the motor was cold or hot, whereas the Bosch plugs produced weak numbers until the head temperature got good and hot. The stockers fell in between, exactly as expected. This resulted in extremely consistent numbers for the Ubers, whereas the Bosche plugs varied almost 5hp between cold and hot cylinder temps.

This was also reflected on the higher end, in a slightly different way. On a dyno, where there is no air flowing over the radiator or heads & fins, the motor heats up considerably hotter than it would on the road. In fact, the data showed that by the 3rd or 4th WOT pull, the motor became heat soaked and the stock plugs began to lose HP. The Bosche plugs actually did the opposite - posting their best numbers once the motor got heat soaked - a temperature not likely to be seen on the road. The Ubers, posted virtually the same number on every run. With all plugs, the peak HP numbers were about the same (remember - the motor was tuned using the stock plugs - and yes, the plugs did have a direct effect on the A/F ratio).

So, yes, iridium does make a difference. But you have to look a bit beyond the WOT runs to understand why.
 

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Tapper said:
iCe said:
Tapper said:
Actually, the plugs do make a difference, but mostly at RPMs less than 4000. At peak horsepower, they don't matter quite as much. There are also other effects that play into the decision.
Did you include a set of stock plugs in the test?

The electrode on the two different Iridium plugs that I have looked at, NGK and Uber, is not ALL Iridium. In fact, the percentage of Iridium tip compared to the overall length of the center electrode is very low and therefore the conductivity benefits that people talk about are all but nil. It's got a little 1/8th-3/16th inch tit of Iridium welded on the tip. The center electrode is a lot longer than that (for obvious reasons). So I'm not so sure that is what makes them spark better, if they spark better than the stockers. I don't think that anyone has done that test. It wouldn't surprise me if the stock plugs are better than any of them because their tip is pointed which should lead to a better spark. You get the SAME THING as the Ubers in NGK for 1/2 the cost. And like I said, I don't think either are better than the stock plug. Possibly worse from a performance perspective. That's just an opinion though.
We did indeed include a stock set of plugs. I worked on finishing up the article last night, I'm almost done. So soon now :)

Actually, the iridium does make a difference. Remember - the iridium is intended to affect the "potential" of the air gap in the plug, not the direct metal to metal contact. Most of these plugs contain a thin wire electrode plated in iridium/rhodium alloy. The Ubers have a welded iridium pad on the tip of the ground, the stockers have a platinum ground tip.

The issue is, that the amount of electricity required to produce a spark, is a function of the potential of the air gap (in volts). The better conductor each end of the gap is, the lower the potential is, and the easier it is to produce a spark there. So, an iridium/iridium gap will spark at a lower voltage than an iridium/platinum, platinum/platinum, etc. Thus, if the potential is lower, and the voltage remains the same, the spark is larger.

We didn't really see the spark size translate into maximum produced horsepower so much, but we did see it translate into peak numbers that were not tied to the head temperature. That is, the Ubers produced max horses whether the motor was cold or hot, whereas the Bosch plugs produced weak numbers until the head temperature got good and hot. The stockers fell in between, exactly as expected. This resulted in extremely consistent numbers for the Ubers, whereas the Bosche plugs varied almost 5hp between cold and hot cylinder temps.

This was also reflected on the higher end, in a slightly different way. On a dyno, where there is no air flowing over the radiator or heads & fins, the motor heats up considerably hotter than it would on the road. In fact, the data showed that by the 3rd or 4th WOT pull, the motor became heat soaked and the stock plugs began to lose HP. The Bosche plugs actually did the opposite - posting their best numbers once the motor got heat soaked - a temperature not likely to be seen on the road. The Ubers, posted virtually the same number on every run. With all plugs, the peak HP numbers were about the same (remember - the motor was tuned using the stock plugs - and yes, the plugs did have a direct effect on the A/F ratio).

So, yes, iridium does make a difference. But you have to look a bit beyond the WOT runs to understand why.
Remember - the iridium is intended to affect the "potential" of the air gap in the plug, not the direct metal to metal contact.
Ah... I didn't think about that. I was thinking overall conductivity... I would have thought that the fine point of the stock plugs would make it easier to conduct a spark. Apparently not. Looking forward to the report...
 

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Actually, sharp points and edges are critical to making good spark on all spark plugs, so you're right in that respect. One of the main reasons plugs wear out at all, is that the edges lose sharpness as the metal is ionized by the spark. This is why very hard metals like platinum and iridium are desirable - they hold their edges longer, and have more electrons to ionize than simple steel does. Way more in fact.

Iridium (actually, the alloy of iridium and rhodium) is generally superior to platinum, because it is a better conductor (more electrons available in the outer valence shell), and because when alloyed with rhodium, iridium forms an extremely hard metal. In fact, iridium has only come into use since the development of plasma welding - before that, you couldn't get it onto a plug.
 

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interesting that you mention a spark plug can affect the air/fuel ratio. Looking forward to your article Tapper. Thanks, Lep
 

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Tapper said:
Actually, sharp points and edges are critical to making good spark on all spark plugs, so you're right in that respect. One of the main reasons plugs wear out at all, is that the edges lose sharpness as the metal is ionized by the spark. This is why very hard metals like platinum and iridium are desirable - they hold their edges longer, and have more electrons to ionize than simple steel does. Way more in fact.

Iridium (actually, the alloy of iridium and rhodium) is generally superior to platinum, because it is a better conductor (more electrons available in the outer valence shell), and because when alloyed with rhodium, iridium forms an extremely hard metal. In fact, iridium has only come into use since the development of plasma welding - before that, you couldn't get it onto a plug.
Yep... I looked all that up weeks ago. To be honest I figured the difference in properties was going to be nil. It was quite the opposite. Iridium plugs, in theory, should last quite a bit longer than platinum... (have to admit that I didn't realize that it was an alloy though.)
 

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Yeah. Iridium by itself is much more conductive than Platinum, but not significantly harder. It has a 600 degree higher melting point though. But alloyed with Rhodium, it forms a crystal structure that's extremely hard

So the combination of high temperature resistance, excellent conductivity, and very high tensile strength make the alloy nearly perfect for spark plugs. Platinum has good conductivity, but a lower melting point, and it's pretty malleable (that's why it's used in jewelry).

The ridiculous thing is, that people are throwing these iridium plugs away every 8000 miles. At that age, they're still nearly brand new. I just brush mine off with a brass brush, and crank em right back into my bike. Hell, even the cheapie platinum plugs should last 12,000 or 15,000 before they're ready to scrap.
 

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plugs

you can get these(NGK (BKR5EIX-11)on club plugs.com for 5.99
 
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