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Re: Fancy and Exotic spark Plugs... another myth for your $$$
dot1dot2   10/21/2011 1:21:32 PM
I've never used the 4 prong platinum plugs but have had very good results with the Bosch single prong. Case in point: 1989 Saab 900 basic 4 cyl with old style distributor, was averaging 25-27 mpg, I changed 2 things, the plugs and the plug wires and consistantly got 33mpg for 1.5 years until I had a mechanic do a tune-up... was never quite the same after that. During the time of the great milage I had a long commute, 73 mi one way, and checked my milage every month.

I will add that my mechanic argued with me that the plug wires could not possibly impact milage but I put them in because the package said "saves gas"... these had an extra thick insulation and that is all I remember about them.

My daughters Saab 9000 could not use platinum tip plugs due the the setup with a coil for each plug... the mechanic said we would burn up the coils in a week.




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Spark Plugs Cost You???
melllowfelllow   10/21/2011 11:25:03 AM
Two comments:

1. The vast majority of problems that occur on older vehicles are related to the last maintenance action [or vehicle 'event'] - incorrectly performed, 'failure root cause' not identified, incorrect parts, etc.

2. The ignition system is a SYSTEM. Replace any part of it with incorrect components - no matter how 'good' [or well advertised] they might be - is asking for trouble.


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A great car?
Dave   10/21/2011 10:22:23 AM
I had to chuckle after reading your post. You start by saying your Mercedes is a great car but by the time I was halfway through, I couldn't help but think I would never buy a Mercedes.

I've had one DOA AC Delco sparg plug over the years but can't recall one failing prematurely. But my old school general rule of troubleshooting is to start with the easiest to replace and least expensive component. Today, OBD diagnostics does a decent job of cluing you in as to what is the problem. That's saved me thousands of dollars in the last 10 years.

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Re: mercedes
Tex_J   10/21/2011 9:43:55 AM
I ran afoul of the Bosch platinum plugs in a Chrysler engine.  One of their claim was low firing voltage.  Well it was in one polarity but not the other.  The Chrysler engine used one coil to fire two plugs.  Guess what.  That fires half of the plugs in reverse polarity.  The Bosch plugs only worked for a few weeks before I had misfires.

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John   10/21/2011 9:28:58 AM
Troubleshoot.. troubleshoot.. troubleshoot.  Given the engine takes in air.. it can only be a problem of fuel delivery or spark and spark is usually easier to test.    Spark takes the path of least resistance so how could multiple conductors help.  If the plug is fouled.. inspect and determine why.

Anyway... biodegradeable wiring harness?  Really??  I have a 96 Cadillac and the factory battery cables are still in great shape. 

My folks had a 87 mercedes. diesel 4 cylinder and it has some odd things on it that could have been simplified.

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Re: Fancy and Exotic spark Plugs... another myth for your $$$
Jason   10/21/2011 9:28:14 AM
It is amazing at how true your statement at the end is Amclaussen!  It reminds me of a Gilette spoof commercial selling a 12 bladed razor.


Back to the topic however, it has never surprised me that companies have started going cheap on materials yet more complex on designs lately.   These plugs are just another example of what can happen when new thinking comes in, but old thinking stays for the materials side of things.  I am sure that when, or if, any simulations were done on these plugs that the performance was great!  However, I am sure that this was under ideal materials and probably didn't take into account imperfections at the plant level.

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Fancy and Exotic spark Plugs... another myth for your $$$
Amclaussen   10/20/2011 4:41:00 PM
James and Rob: I fear that these 4-ground electrodes plugs malady if the result of young monkeys working feverishly in the Marketing and Engineering depts. at Bosch (or Siemens or any other)...

Multiple Ground Electrode plugs.

Developed in order to maintain the spark jumping from the central electrode at least onto one ground electrode in the dirty, oily-fuel needed in those two stroke grasscutting engines, back when ignition systems were notorious for their limited output...

BUT MORE THAN ONE single ground electrode only shrouds and shadows the flame front initiation, REDUCING the performance, certainly not enhancing it in any way. (Well, they may enhance the plug manufacturer sales!). Truly good old racing mechanics even used plug indexing to avoid the ground electrode shrouding the spark, the best ones by carefully choosing every plug from a big, big box; the lazier ones just resorting to "indexing-washers" (and losing the best placement of the firing end!).  BTW, real racing engines use NOT not even one single ground electrode, but a flat, round surface electrode around an almost flush central electrode, called "surface discharge" electrodes... No shrouding at all!

(It is a pity those only work at VERY HIGH compression ratios, extremely high RPM's, idling is over a few thousands RPM's, and a host of other conditions that are ONLY seen in truly race-designed engines (more like F-1...)

At a recent automotive industry Expo in Mexico City, I strongly questioned the salesmen from a (in)famous german company (you know which one) for promoting such a wrong product application: it only works better in 2-stroke oil-mixed fuel engines, not in a car engine, unless the car owner pretends to keep the same plug set for many years of use, in which case the extra ground electrodes could be of some help)... After explaining to them how the flame front is propated from the spark kernel and it initiates the combustion, finally the crowd assisting to the talk gave me their approval. Sorry, no more snake oil or gimmicks for me!

Another misconception is that those special metallurgy electrodes "produce extra power", when actually a thinner electrode can only produce a smaller spark kernel, and frequently is prone to overheating in Supercharged or turbocharged engines... causing pre-ignition. Turbocharged engine fans already have discovered this, and now favor the older plug designs with larger diameter central electrodes, the standard ones that still need to be changed more frequently in order to keep the engine working properly. There is NO free luch!

Iridium, Rhodium or even Gold electrodes do NOT produce more power (but could raise profits for the plug manufacturers, from overly enthusiastic power hungry but ignorant aficionados paying for them).  WHERE the platinum, iridium and similar metallurgy really get, is a much longer lasting plug, arising from their higher corrosion-erosion resistance, Perfect for installing and forgetting, but definitely NOT more horsepower or additional fuel economy!

The possible explanation for your 4 electrode plugs being eroded in a short time, is that the metallurgy of the ground electrodes was probably meant to "shed"  by itself, in order to "renew" its firing surface fast, and keep itself clean against the excessive deposits from the fuel with oil mixture needed in two-stroke engines, and proper when the ignition system is relatively weak (like those in lawnmowers) but NOT in a high energy car ignition!

Now, I'm not surprised that Bosch (and too many other compañies) are exploiting the looks of those 4-electrode plugs, as it appears that nowadays, engineers are being replaced by monkeys everywhere. ( I can almost hear the CEO's saying: If a two electrode plug looks good, a three one should look better... then a FOUR one must sell MUCH better, ok, so let's do it.  Wait! how about a FIVE one?)

amclaussen, Mexican Petroleum Institute.

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