Spark Plug Comparison

[Solina Dave]

Regarding my '78 GL1000, the owners manual specifies the NGK D8EA for U.S. bikes, and NGK DR8ES-L for Canadian bikes. These are nickel spark plugs. For what it's worth, mine is up here in Canada. Why they're country specific I don't know, unless it's climate related.
At any rate, NGK customer support gave me a reply to this inquiry:

I have a 1978 Honda GL1000 Goldwing motorcycle. The owners manual calls for an NGK D8EA for a U.S. motorcycle, and an NGK DR8ES-L for a Canadian model. I have at times used either plug in my motorcycle. What is the technical difference between the plugs? Why are there two different plugs specific to U.S. or Canadian models? And are these plugs compatible with either machine, or is there a technical disadvantage in using one over the other. If either plug is compatible, why do they have different numbers? Any details that you could provide for me would be most welcome.

I got this reply:

The D8EA is a non-resistor spark plug in a heat range of 8, the DR8ES-L is a resistor spark plug and the –L stands for ½ a heat range colder. My listing shows D8EA to be used for a standard nickel spark plug or the Iridium IX DR8EIX for a high performance spark plug. The recommended gap is 0.028”.

The D8EA is obviously, at least 1978 technology. Has anyone had occasion to use the Iridium IX DR8EIX spark plug, which by the way is nearly 4 times the price of the D8EA spark plug, did you notice a significant performance change, and what would those changes be?

This topic has "sparked" my attention.....................Dave

PS....Just to clarify, the ad info. that I've read specifies 0.032" gap for the Iridium spark plug.

[ekvh]

I run the iridium in my stock 77. It helps keep it running better at idle from a rich condition, so it's better but masking a separate issue.

I never knew about the L designation. I would have thought the suggested plug be half a step hotter for Canada??

In my hybrid bike, I tried a 7 but it was too hot. My 8's are a bit darker chocolate, the 7 turned them pretty white. I may have to try a 7 with the L designation.

[WingAdmin]

Regarding my '78 GL1000, the owners manual specifies the NGK D8EA for U.S. bikes, and NGK DR8ES-L for Canadian bikes. These are nickel spark plugs. For what it's worth, mine is up here in Canada. Why they're country specific I don't know, unless it's climate related.
At any rate, NGK customer support gave me a reply to this inquiry:

I have a 1978 Honda GL1000 Goldwing motorcycle. The owners manual calls for an NGK D8EA for a U.S. motorcycle, and an NGK DR8ES-L for a Canadian model. I have at times used either plug in my motorcycle. What is the technical difference between the plugs? Why are there two different plugs specific to U.S. or Canadian models? And are these plugs compatible with either machine, or is there a technical disadvantage in using one over the other. If either plug is compatible, why do they have different numbers? Any details that you could provide for me would be most welcome.

I got this reply:

The D8EA is a non-resistor spark plug in a heat range of 8, the DR8ES-L is a resistor spark plug and the –L stands for ½ a heat range colder. My listing shows D8EA to be used for a standard nickel spark plug or the Iridium IX DR8EIX for a high performance spark plug. The recommended gap is 0.028”.

The D8EA is obviously, at least 1978 technology. Has anyone had occasion to use the Iridium IX DR8EIX spark plug, which by the way is nearly 4 times the price of the D8EA spark plug, did you notice a significant performance change, and what would those changes be?

This topic has "sparked" my attention.....................Dave

PS....Just to clarify, the ad info. that I've read specifies 0.032" gap for the Iridium spark plug.

The D8EA is a heat range 8, where the DR8ES-L is a heat range 8.5 - so one half heat range colder, I expect for the slightly colder environments. Too cold a plug can cause fouling, too hot a plug can cause detonation.

[ekvh]

I'm probably missing something here, but why would use a colder plug in a colder environment? Wouldn't it be the other way around?

[WingAdmin]

I'm probably missing something here, but why would use a colder plug in a colder environment? Wouldn't it be the other way around?

That's a good point, and I wasn't even thinking about that when I wrote it.

That would make sense - in a hotter environment, you want a colder plug that removes heat quicker into the head, to prevent detonation.

So I don't know why Honda did this!!

That said, the difference between an 8 and an 8.5 is really not a lot. 0.5 heat range means the ability to remove 35°C to 50°C from the combustion chamber.

[Solina Dave]

I just read through this Wikipedia article once, and I thought you might be interested. https://en.wikipedia.org/wiki/Spark_plug#Heat_range There's a lot of information to absorb, so I'll have to examine it closer. I didn't notice any reference being made to the effects of outside temperature, but maybe it's in there somewhere.
WingAdmin, down near the bottom of this article there's a comment that racing cars often used certain plugs for startup, and a different plug for racing, after the engine warmed up. Did you do that when you were in the pits? Just curious.

.................Dave

[redbug]

I'm probably missing something here, but why would use a colder plug in a colder environment? Wouldn't it be the other way around?

That's a good point, and I wasn't even thinking about that when I wrote it.

That would make sense - in a hotter environment, you want a colder plug that removes heat quicker into the head, to prevent detonation.

So I don't know why Honda did this!!

That said, the difference between an 8 and an 8.5 is really not a lot. 0.5 heat range means the ability to remove 35°C to 50°C from the combustion chamber.

Maybe it is ngk and not Honda, extended high speed they recommend a D9, and then below 5c a D7,maybe the 8.5 is a split the difference. Now I am confused. Then ngk chart for you is theD8EA or the DR8EIX. Then again...

[Solina Dave]

It's not much of a surprise that there's confusion. A little bit of industry standardization would be nice for a change. Straight out of the Wikipedia link that I posted, it states: "The heat range of a spark plug is typically specified as a number, with some manufacturers using ascending numbers for hotter plugs, and others doing the opposite – using ascending numbers for colder plugs."

As if I'm not confused enough...................Dave

[WingAdmin]

It's not much of a surprise that there's confusion. A little bit of industry standardization would be nice for a change. Straight out of the Wikipedia link that I posted, it states: "The heat range of a spark plug is typically specified as a number, with some manufacturers using ascending numbers for hotter plugs, and others doing the opposite – using ascending numbers for colder plugs."

As if I'm not confused enough...................Dave

That's correct.

The heat range numbering system used by spark plug manufacturers is not universal. For example, a 10 heat range in Champion is not the same as a 10 heat range in NGK nor the same in Autolite.

Some manufacturers numbering systems are opposite the other - for Champion, Autolite and Bosch, the higher the number, the hotter the plug. For NGK, Denso and Pulstar, the higher the number, the colder the plug.

When making spark plug heat range changes, it is better to err on the side of too cold a plug. Running too cold a plug can only cause it to foul out, whereas running too hot a plug can cause detonation and severe engine damage.

[Solina Dave]

The D8EA is obviously, at least 1978 technology. Has anyone had occasion to use the Iridium IX DR8EIX spark plug, which by the way is nearly 4 times the price of the D8EA spark plug, did you notice a significant performance change, and what would those changes be?

Nobody seems to be answering that question.
Does anyone have a first hand knowledge and evaluation of the NGK Iridium IX DR8EIX spark plug (that's a mouthful)? It's 4 times the price, but is it 4 times better? Or is it just more marketing crap to suck you into buying the more expensive plug? It would almost have to make my motorcycle fly, to convince me to pay that much more for a spark plug.

.........Dave

[redbug]

The D8EA is obviously, at least 1978 technology. Has anyone had occasion to use the Iridium IX DR8EIX spark plug, which by the way is nearly 4 times the price of the D8EA spark plug, did you notice a significant performance change, and what would those changes be?

Nobody seems to be answering that question.
Does anyone have a first hand knowledge and evaluation of the NGK Iridium IX DR8EIX spark plug (that's a mouthful)? It's 4 times the price, but is it 4 times better? Or is it just more marketing crap to suck you into buying the more expensive plug? It would almost have to make my motorcycle fly, to convince me to pay that much more for a spark plug.

.........Dave

Dave, I keep pretty good logs but what you are asking is almost impossible to answer. There are to many variables. Stay stock with the plugs DRE8 or if you want a 100,000 plug go to the iridium's. The only benefit is not having to change them as often.

[Solina Dave]

PS....Just to clarify, the ad info. that I've read specifies 0.032" gap for the Iridium spark plug.

My apologies, and a correction on that. I was looking at info. provided by Advance Auto Parts. They specified the NGK Iridium IX DR8EIX spark plug as having a 0.032" gap. Everyone else, that I'm coming across including NGK themselves specifies 0.028". So I would go with that.

Sorry about that.............Dave

[Solina Dave]

Does anyone have a first hand knowledge and evaluation of the NGK Iridium IX DR8EIX spark plug (that's a mouthful)? It's 4 times the price, but is it 4 times better? Or is it just more marketing crap to suck you into buying the more expensive plug? It would almost have to make my motorcycle fly, to convince me to pay that much more for a spark plug.

Dave, I keep pretty good logs but what you are asking is almost impossible to answer. There are to many variables. Stay stock with the plugs DRE8 or if you want a 100,000 plug go to the iridium's. The only benefit is not having to change them as often.

I'm inclined to agree with you redbug. I'm probably just flogging a dead horse here. I was simply curious to see if anyone had been blown away by the performance improvement when using the Iridium plug. But I think you're right, that for most of us, it's probably the improved mileage possibilities that might appeal. I've always been satisfied with the basic OE plugs plugs performance. And besides, I like changing my plugs. It offers us time to bond.

Keep a look-out, and ride safe...................Dave

[WingAdmin]

I wouldn't want 100,000 mile plugs in my bike. After 100,000 miles, you'd never get them out of the head!

[redbug]

I wouldn't want 100,000 mile plugs in my bike. After 100,000 miles, you'd never get them out of the head!

Well I stand corrected there 40 to 50 thousand miles. Myself it is 4000 as per operators manual.

[ekvh]

Randakk has the same info on his site, that the "L" is 1/2 step colder.

[Solina Dave]

WingAdmin, You might have missed it earlier when I asked you this question, so I'll run it by again.
Down near the bottom of this article, https://en.wikipedia.org/wiki/Spark_plug#Heat_range there's a comment that racing cars often used certain plugs for startup, and a different plug for racing, after the engine warmed up. Did you do that when you were involved with racing cars. Just curious as to how common this is done in pro racing.

Thanks.........................Dave

[WingAdmin]

WingAdmin, You might have missed it earlier when I asked you this question, so I'll run it by again.
Down near the bottom of this article, https://en.wikipedia.org/wiki/Spark_plug#Heat_range there's a comment that racing cars often used certain plugs for startup, and a different plug for racing, after the engine warmed up. Did you do that when you were involved with racing cars. Just curious as to how common this is done in pro racing.

Thanks.........................Dave

Nope! We changed plugs before each race, but never between warm-up and qualifying or racing.

[eklimek]

Changing plugs between warm up and race is a recognition of carburetion richness and poor vaporization in a cold manifold at idle. Running warm up plugs helps reduce fouling.

Plugs can be selected for steady state conditions. Racing with higher rpm and near full throttle approaches this condition. Its the cold start, low speed, poor combustion chamber conditions with mixing of intake and exhaust found with valve overlap of the racing cam that is hard to ignite.

The Goldwing has the challenges of low speed and varying conditions.

Preignition is premature ignition similar to advancing the timing. It results from a hot surface in the chamber, commonly a spark plug or carbon deposit. Incandescent particles projecting into the combustion chamber lead to detonation.

Detonation is a complex problem not readily solved by a spark plug change. It is autoignition of the charge not yet consumed in the normal flame front reaction. Detonation may lead to overheating of the spark plug with preignition before the spark. The resultant pressure wave can be damaging and does not contribute to efficiency as the increase pressure Is not effectively used to drive the piston down. This generates a pressure wave about 3 milliseconds that is audible. This drives up gas temperature.

Reducing detonation is accomplished by reducing end gas temperature : inlet temperature, fuel distribution, coolant temperature, increasing compression time, decreasing exhaust back pressure, humidity, water injection, combustion chamber "squish", increasing number of sparkplugs. Octane and bore size also affect it.

Detonation is dealt with in more detail for those interested in
Chapter 3
C Fayette Taylor
January 1984
Voulme 2
The internal combustion engine in theory and practice
Revised edition
MIT Press
isbn 0-262-20052-x

[Solina Dave]

eklimek.....Thank you very much for that excellent write-up, and all that information. I'll have to read through it a couple of times to really get a grip on it, but it does make things clearer for sure. And also, I personally doubt that I'll have to look for the book that you made reference too for any more detail.

Thanks again....................Dave