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  #31  
Old 04-24-2003, 03:27 PM
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Well, no, but perhaps a descendant...
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  #32  
Old 04-24-2003, 03:45 PM
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I've tried the +4s twice now ( I'm a slow learner).. Both times, I had rough idle issues..

I tried it in my Jeep, and Buick.. I won't try them a third time...

Jay
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  #33  
Old 04-24-2003, 03:54 PM
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Smile Wanna see a fried Bosch Platinum anyone?

I have been having some minor performance problems with my 1984 500SEL. I chased a few things down without much luck. Out of my personal and professional love of arc phenomena, I read this thread. I bought semi-fancy Bosch +2 platinums last summer, and have clocked about 4000miles since. I pulled one last night to check their condition. Aside from looking a bit rich, the gap looked really big. It took a few minutes then I figured out why. Because the thin-wire platinum center conductor WAS GONE. Turns out every plug had no center electrode left. They dun arced plum off. I am going to take a picture and post so everyone can see. Eight "period" plugs later, I'm lightin' up the rear end.

Other than that, I think there is probably a big difference in what plugs work well in a 1984 5.0L and a 2002 5.0L engine. In my understanding, a 2002 engine is far more efficient at burning the charge (swirling, turbulence, squish bands, fuel mapping, etc.) therefore less plug damage via unburnted fuel.

Incidently, unless a getter (secondary electron and/or hole donor) is used, ALL electrodes will "plate" off, so to speak. The arc is stuff going from one side to the other.
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  #34  
Old 04-24-2003, 04:15 PM
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agara

I hope you realize that the centre electrode does not protrude past the porcelain when these plugs are new.
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  #35  
Old 04-24-2003, 04:44 PM
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Huh. Surface electrode. Well, but...

Yes, the center electrode did not burn off 'cause it was never really there. I feel a little silly, and probably now no one will believe me that these spark plugs were not working very well after 4000 miles. There is always the possibility that my engine runs rich, which was the root cause of the plugs fouling. In any case, new plugs work better.

And now I much more fully appreciate the comment that the gap can't really be changed. I am under the general impression that late model vehicles have higher energy ignition systems which allows for wider plug gaps (which gives larger arcs, better burn, etc.) So does this possibly explain why these may not be suitable for certain generations of ignition systems/engines? That is, the gap is just a little too big off the shelf?
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  #36  
Old 04-24-2003, 05:20 PM
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Well, if Bosch lists a plug for the make /model/ year and engine, then it should work.
As I said before, platinum plugs where invented in response to longer change intervals, i.e. less electrode wear with platinum.
There may be some engines, that simply do not respond well to these plugs.
In my experience you can try different ones ( make, materials, etc. ) and stick with what ever works best for you.
Btw. I believe that european cars seem to have had a weak ignition system in the past. It appears, when most North American automakers were going with large gaps, 0.045 - 0.080", the europeans were still specifying small gaps like 0.028 - 0.032".
But who am I to say, my name isn't Bosch, or Champion, or Nippondenso, etc.
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  #37  
Old 04-24-2003, 08:10 PM
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Rich running will foul platinums as fast or faster than other plugs. Carbon fouling will lead to misfire, and low power, etc.

Iridium will work pretty much like platinum, but is more expensive and harder to work with -- will probably last longer, too since it is physically harder. Much cheaper than it used to be, since I have several gold/platinum/iridium crowns in my mouth now -- didn't cost that much (cheaper than porcelain).

Not all plugs will work well in all engines, and some will be more sensitive to actual operating conditions than others. I've got Bosch platinums (single electrode) in the 280 SE, and it runs fine. Not perfect, but I've not gotten the valve adjust done yet, nor is the mechanical advance in the distributor quite right. No knock, even on midgrade (this may change if the valves are tight), PLENTY of power, and 15-16 mpg mixed driving. They will stay in there!

I put plus 4s in the 300TE on the advise of my friend the MB trained mechanic, he uses them in all the cars he services. He says rough idle is a mixture/ignition problem, not the plugs.

Peter
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  #38  
Old 04-24-2003, 10:02 PM
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I bet diesel owners reading this are smiling ear to ear......
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  #39  
Old 04-24-2003, 10:49 PM
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Quote:
Originally posted by mbtjc
I bet diesel owners reading this are smiling ear to ear......
Yeah..........., but they probably have " issues" of their own.
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  #40  
Old 04-25-2003, 08:27 PM
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Such as the '85 Volvo turbodiesel sitting too close to the garage door (so I won't let my mother park her car in there, she backs into things) that failed to start on very cold day in January and has refused to start since?

Peter
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1987 300D Turbo killed 9/25/07, 275,000 miles
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  #41  
Old 07-20-2003, 01:31 AM
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There is a lot of marketing hype about spark plugs. As usual, misguided hopes which result just cost us money, and don’t produce real results.

In my testing, the Bosch +4 and the NGK 3’s only advantage is allowing 4, or 3, opportunities for a single spark path, the one better path at any given time get the nod. That may explain some good impressions about the plug, (i.e., a spark path more easily presents itself) but I ask, at what cost? …and why? …when far better spark technology is available. This technology makes marginal most of our mussing about plugs. However, I would recommend NGK because they have the finest ceramics, are well made and are not too costly.

MB spark is amongst the highest energy in the first place. However, ever seen most sparks at the plug? Add the effect of compression, and things seem even less impressive. The bottom line is that we are trying to affect as many air-fuel molecules at one time to effect a positive ignition each and every time. Nothing more, nothing less.

The way to affect the most air/fuel molecules is with increased energy, not increased duration. A stringy spark lasting a longer time still affects only a fraction of the air/fuel molecules than the massive plasma sphere produced with a peaking capacitor. It ignites the leanest and richest of mixtures, and one does not have to use costly spark plugs with gimmick multiple spark pathways. Install DirectHits and stop worrying about the performance of your sparkplugs.

Mark Shinnick
www.mastertimer.com
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  #42  
Old 07-20-2003, 09:45 AM
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Food for thought.
Mercedes engineers spent much time making their cars run good, smoooooth, and with good mileage under all conditions.
(this also applies to other manufactures)
If they put a plug in at the factory, they know it will work. I'm not smart enough to second guess them so I will allways use what they use. That way, I will always win.
In my shop (we will work on any brand car) we always use what the manufacturer used. We never have a plug issue. In fact, I won't even work on a drivability problem unless the car has the correct plug.
In a weaker moment, I did try Bosch Plat plugs in my 84 500 SEL (they were given to me by a Bosch Rep). We went for a ride. Came back and took out the Bosch Platium, reinstalled the W9DC used plugs. Took another ride with the rep. Came back and the rep paid me for an hours labor, gave me a new set of W9DC plugs and left.

I knew the Bosch Platiums wouldn't work because I had tried them. The rep said something else must have been wrong, or I had gotten a bad plug and he would pay me to try them again. How could I refuse.
By the way, my 500 SEL just averaged over 20 mpg on a trip from NC to Flordia with speeds usually between 75 and 85 with the Air on and 4 people (all grown-up). I think that is OK for a car this big going that fast for 12 hours and it has W9DC plugs in it and it has 257,000 miles.

Moral to the story.
Always use what the manufacturer used and you can't go wrong.

Paul McKechie
84 500 SEL
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