Iridium plugs on an FJR?

[SCRider]

Here is a drawing from my motorcycle electrical book. This is easier to read than the wiring diagram from the FJR manual. DIS stands for distributorless ignition system. As you can see there is no ground (battery ground) for either of the spark plugs. The only thing grounded at the battery is the primary winding in the ignition coil. The secondary winding is its own complete circuit The plug's air gap gives the circuit its high resistance (and a place for the spark to form). The cylinder head acts like a giant wire that connects the two plugs electrically. The red arrows shows current flow (yes, I know that it really flows the other way but it's easier to explain going from positive to negative--aka "conventional electron theory") Hope this helps.

Great drawing 3dogs! This makes it much simpler to understand. Basically, the head is just a wire to connect the 2 ground (threaded) sides of the plug together and has nothing to do with the chassis ground.

Oh, I think he was just being sarcastic, he agrees with you....

QUOTE (Zorlac @ Jun 17 2009, 07:01 PM) *

That can't work, the plug bases aren't "grounded".

 

[Fred W]

What cracks me up about that diagram is the arrows showing current flow in the "wrong" direction.

Must be from back in the old "hole flow" theory days...

Not that it matters in the least. What matters is that the two plugs are at opposite polarities and the sparks will jump in the opposite directions. So only one of the two plugs will get the maximum benefit of having an iridium center electrode.

So you decide... is it a waste of money? Maybe. But it isn't all that much compared to some other things we buy on faith.

 

[Bustanut joker]

Why does reading this thread cause my eyes to glaze over and also to drool un-controllably?

Ummm. Because you're a dork holding onto the plugwire while crankin' the engine to test these theory's? :dribble:

:huh:

:jester:

 

[BikerGeek99]

What's a spark plug?

Hell if I know, but they're saying you're supposed to REPLACE 'em??

I got nothin' here.

 

[Rolavine]

What cracks me up about that diagram is the arrows showing current flow in the "wrong" direction. Must be from back in the old "hole flow" theory days...

Not that it matters in the least. What matters is that the two plugs are at opposite polarities and the sparks will jump in the opposite directions. So only one of the two plugs will get the maximum benefit of having an iridium center electrode.

So you decide... is it a waste of money? Maybe. But it isn't all that much compared to some other things we buy on faith.

As I see the schematic, the lower end of the primary will go to a very high voltage when the circuit is broken. This will induce a positive voltate on the lower end of the secondary and a - on the upper. So based on this, I think the arrows are showing current flow from a -V to a +V potential, and that would follow the electron flow model. I'm an electronic engineer and I never think about electron or hole flow at all anymore, I come up with the right numbers without it.

Of course, at his moment I'm writing code for an ARM microcontroller and I can tell you its documentation is more full of holes than the last bit of 'reasoned discourse' I saw put forth by Glen Beck.

 

[CRMH Eagle]

There was a group buy last year on iridium plugs. I joined and obtained new plugs for a good price. After installing the plugs several thousand miles ago the bike still pulls as strong through the entire throttle as the day I installed the plugs. From reading experience of other riders I have gathered these plugs will still last a longer time compared to non-iridium plugs. This means less time on maintenance and more time on the bike.

This all I need to know about iridium plugs. B)

 

[johnny80s]

So if your theory is correct Fred then when you pull your Iridium plugs two will have the white iridium dot on the end and two won't. Can you post some pictures of these after you pull your next set? That might end this debate, but probably not.

 

[3dogs]

So if your theory is correct Fred then when you pull your Iridium plugs two will have the white iridium dot on the end and two won't. Can you post some pictures of these after you pull your next set? That might end this debate, but probably not.

When distributorless ignitions systems came out in the mid 1980 technicians soon discovered that when plugs were changed half of them looked new and the other half had a worn center electrode (normal ware for spark plugs). The plugs that looked new did show metal removed from the under side of the ground electrode.

This is because the paired spark plugs each fire in a different polarity – one like a normal plug and the other in reverse polarity. This causes metal transfer due to ware to be normal on one plug and the reverse on the other. Before technicians understood this some would only replace ½ the spark plugs on the V6 engines that used these early systems. I took pictures of this for an article that I wrote years ago (film-no digital back then) and I can’t find the images. Next time you change the FJR plugs if you look close you should see this wear pattern (assuming that the plugs have enough miles on them).

Here are some links about spark plug firing polarity.

Ford DIS Plugs

NGK Info

 

[C&C]

Here are my iridiums with just over 15,000 miles on them. Left to right are the number 1 through 4 cylinders represented. Note that number two and four cylinder electrodes are slightly eroded (as opposed to one and three are still sharply defined). Is this showing what the discussion is saying about polarity and electron flow direction.

Sorry that the picture is not as perfect as I would have liked (Canon S3 1S, need that S10 1S).

 

[Patriot]

There was a group buy last year on iridium plugs. I joined and obtained new plugs for a good price. After installing the plugs several thousand miles ago the bike still pulls as strong through the entire throttle as the day I installed the plugs. From reading experience of other riders I have gathered these plugs will still last a longer time compared to non-iridium plugs. This means less time on maintenance and more time on the bike.
This all I need to know about iridium plugs. B)

most importantly, your "D" batteries connected to the ignition to fire the plugs will last weeks longer

 

[Fred W]

Here are my iridiums with just over 15,000 miles on them. Left to right are the number 1 through 4 cylinders represented. Note that number two and four cylinder electrodes are slightly eroded (as opposed to one and three are still sharply defined). Is this showing what the discussion is saying about polarity and electron flow direction.
Sorry that the picture is not as perfect as I would have liked (Canon S3 1S, need that S10 1S).

Yes, excellent. Your picture above shows the different wear patterns from the 2 different plug firing polarities. Looking closely you can see that the center electrodes are slightly rounded (eroded) on plugs #2 and #4, and the side electrodes look slightly rounded on #1 and #3. So it follows that #1 and #3 are on the positive side of the two coils and #2 and 4 on the negative sides.

I think this answers Johnny80's question about wear patterns. But it still doesn't answer the question: "Are they worth the extra $$"?

[edit] added below

Here are some links about spark plug firing polarity.Ford DIS Plugs

NGK Info

I just caught that second link and read it. Other than the foolishness about protons colliding with the electrodes, the description of the wear is still the same. But the text indicates that the side electrode is made of some precious metal. It actually says in the 3rd paragraph that it will be platinum and in the 2nd paragraph of the 2nd page infers that there are "double iridium" plugs. I have been unable to find anything on the NGK web site's product descriptions of the iridium plugs that confirms this. That's why I was assuming the side electrodes were not made from precious metal.

Investigating on the NGK web site further. The product description of the Iridium IX plugs that we are using is conspicuous in that it doesn't talk about the side electrode being precious metal, only "Trivalent metal plated" whatever that means.

On the other hand, their description of their Laser Iridium and Laser Platinum plugs specifically mention a platinum disc being added to the side electrode.

Based on that, I think my prior assumptions about the Iridium IX having standard side electrodes is correct.

 

[CRMH Eagle]

There was a group buy last year on iridium plugs. I joined and obtained new plugs for a good price. After installing the plugs several thousand miles ago the bike still pulls as strong through the entire throttle as the day I installed the plugs. From reading experience of other riders I have gathered these plugs will still last a longer time compared to non-iridium plugs. This means less time on maintenance and more time on the bike.
This all I need to know about iridium plugs. B)

most importantly, your "D" batteries connected to the ignition to fire the plugs will last weeks longer

Now there's TWO things I need to know about iridium plugs. Touche.

 

[03HiYoSilver]

It is ironic this subject came up. I just took out my Iridium plugs after 6k miles and put back in the Regular plugs while I was doing the ignition relay install. The MPG's seem to be lower lately and thought for sure I had a bad plug.
Here is what I found after putting in the Regular plugs after a 1/2 tank of fuel (not what I had expected but was surprised).

Keep in mind, this is not scientific but these are my finding thus far:

1- The engine seems to like to run better at lower RPM's with the Regular Plugs.

2- The engine is running overall cooler with the Regular Plugs, now rarely hits the 4th bar (of 6 on GenI) when the fan kicks on even now when the temp's are in the 90's.

3-So far, with this 1/2 tank of fuel, seems to be getting about 20% better mileage. With the Last 2 Tanks with the Regular Plugs, I am getting about 16-20% better MPG.

Now I can not explain this difference but the Iridium Plugs below seemed fine and was very surprised with my experience so far. Even though the Iridium Plugs look Rich in the pictures, they aren't and all look almost identical. They Ran Fine, Very Snappy and can not explain the differences...we'll see next time if they repeat the same results.

 

[08FJR4ME]

So if your theory is correct Fred then when you pull your Iridium plugs two will have the white iridium dot on the end and two won't. Can you post some pictures of these after you pull your next set? That might end this debate, but probably not.

Gosh, I hope so! :sleepysmileyanim:

This is destined for NEPRT.

Ime spinnin, Ime spinning!!!!!!!!!

 

[Fred W]

This is destined for NEPRT.

Really, Dave? Why is that?

I haven't found this discussion (about polarity of ignition coils) ever brought up before in the entire history of this forum.

Now if it is allowed to drift off endlessly into another "when do I replace spark plugs" debate, then yeah, I see your point.

 

[08FJR4ME]

55 post on spark plugs????? just sayin :blink:

 

[Karl]

I've had 4 of these in the tool box for 6 months. Duals worked really nice on my K-bike. Probably will install tonight to see how they do in the feej.

https://www.sparkplugs.com/results_cross.as....y=7&mfid=1

 

[UselessPickles]

I've had 4 of these in the tool box for 6 months. Duals worked really nice on my K-bike. Probably will install tonight to see how they do in the feej.
https://www.sparkplugs.com/results_cross.as....y=7&mfid=1

From the website you linked to:

Some combustion chamber designs (such as a rotary motor) require that the spark plugs have the ground electrode placed to the side of the center electrode rather than below as on a traditional plug (see photo). This firing tip design tends to erode the tip of the ground electrode faster than a traditional plug. Erosion at these points creates a larger gap between the center and ground electrodes, causing plug misfire. Thus, by having more ground electrodes, you extend plug life. It is important to note that multi-ground does not mean multi-spark, there will still only be one spark at a time. Therefore, a multi-ground plug will not perform any better and may actually perform worse than a traditional plug, unless the engine is designed for a multiple ground plug.

 

[Fred W]

55 post on spark plugs????? just sayin :blink:

Well, at least 2 of them didn't say anything...

I've had 4 of these in the tool box for 6 months. Duals worked really nice on my K-bike. Probably will install tonight to see how they do in the feej.
https://www.sparkplugs.com/results_cross.as....y=7&mfid=1

Having a multi-side electrode, or surface fire plug (that's what Mazda rotaries actually use) may be one way to have the side electrode last as long as a center iridium electrode. I don't see them running any worse unless the heat range is effected negatively.

 

[Karl]

55 post on spark plugs????? just sayin :blink:

Well, at least 2 of them didn't say anything...

I've had 4 of these in the tool box for 6 months. Duals worked really nice on my K-bike. Probably will install tonight to see how they do in the feej.
https://www.sparkplugs.com/results_cross.as....y=7&mfid=1

Having a multi-side electrode, or surface fire plug (that's what Mazda rotaries actually use) may be one way to have the side electrode last as long as a center iridium electrode. I don't see them running any worse unless the heat range is effected negatively.

I ran them in the BMW out to 15K and never had any problem. They cleaned up nice on the wire wheel and after a re-gap, could have gone another 15K I reckon. But since they're out already, might as well toss them unless you're a real tight-arse.