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Old 05-30-2003, 07:05 PM
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Spark Plug Debate - adding fuel to the fire, pun unintended

Saw this on I suppose the other question would be "it may not hurt the engine but will it make it run better?" Their answer I suppose is that Bosch guarantees your car will run better on Plat +4's

Benz Bosching

Q--Recently it was time for the 60,000-mile service in my ’99 Mercedes E-Class wagon. I asked the dealer if they could install the Bosch Platinum+4 plugs. They said only the original platinum plug was recommended. I called Mercedes’ technical service and they said it would hurt the engine because the +4 plugs run hotter. I e-mailed Bosch with the question about using the plug — after all, they have a part number for my car — but have not received a reply. Perhaps you could forward this question on to Otto Stefaner at Bosch to see if he can shed some light on this mystery? Is it possible to get a confirming note from Mercedes?

A--We did as you asked and here is what Mr. Stefaner has to say: “We cannot expect the vehicle manufacturer's technical service people to recommend spark plugs that do not show their company’s brand. The explanation, however, that Platinum+4 spark plugs run hotter, is incorrect. Just like other spark plugs, Platinum+4 come in different heat ranges. That means there are colder versions available for engines that require colder plugs, and hotter ones for engines that need them hotter. Bosch determines which Platinum+4 has the proper heat range for a specific engine, and that's the one we recommend. This way, the recommended spark plugs won’t hurt the engine.”
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Old 05-30-2003, 08:30 PM
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Join Date: Apr 2002
Posts: 321
there is really no need for platinum electrode spark plugs for the automobile engine. and the bosch platin +4 is a most egregious joke. it is a gimmick intended to remove more dollars from your pocket than you need to have removed.

platinum found it's way into spark plug electrodes in ww2. upon the observation that platinum would resist lead salt fouling somewhat better than nickel alloy electrode spark plugs in the heavily tetraethyl lead-additive avgas blended for the compound turbocharged/supercharged aviation engines of the era.

on the other hand, platinum had more pronounced fouling[gap bridging] problems than nickel alloy electrode plugs as platinum has a peculiar affinity for attracting nodules of certain lube oil additives[zinc dithiophosphate in particular].

i worked with AC and autolite when they introduced spark plugs with electrode attachments of platinum. their thought was that these plugs would outlast nickel alloy electrode spark plugs, allowing a set of plugs to last 100,000 miles. i know that in my last meeting in flint the AC engineers admitted that the those plugs never made that mileage mark and that there was virtually a secret campaign to freely change those spark plugs whenever the dealer could get the car so that the illusion could be created that the original equipment installed plugs lasted that long.

NGK may have started this precious metal nonsense for automotive application engines. sheer press agentry. and my engineering records can prove it. my favorite story in this regards involved daimler-benz om407h engines converted to run on CNG for transit bus service in Perth, Western Oz. I became involved because the standard plug fitted by D-B[a champion L82YC] had a hard time lasting a week.

I supplied the transit bus operator special plugs using gold palladium electrodes. shortly after installing them, the transit bus operator asked me if we could furnish spark plugs with platinum electrodes like NGK's, because they started the engine so much better. though disbelieving the appraisal of the transit bus fleet operator, we fabricated plugs identical to the electrode, heat range design of the NGK plugs and then traveled to Perth to install them and check out the engines.

before we installed our plugs, we asked to have the bus outfitted with the NGK's trialed for us. what a surprise. we timed the starting cycle. with the NGK's it took over 3 minutes to start the engine. my associates and i said to ourselves, "...and this is thought to be good?"

before we put our platinum plugs in the engine, i was taken aside by the maintenance director who asked me how long our plugs would last. i said, i had no idea. then i asked him, how long were the NGK's lasting? and i received a very honest reply, "we're lucky if they make 10,000km."

we were shown used NGK plugs and they all exhibited severe electrode erosion.

we examined the engine and we found why it might have been the case that platinum electrodes were able to start the engines faster[albeit too slowly]. the engines were outfitted with propane carburetors as opposed to cng carburetors. and the fuel valve was slaved to a shut-off governed by battery amp draw-down.

long and the short of it was that the platinum electrodes finally started the engines faster because of catalytic ignition.

once the engine's fuel delivery system was remedied with a cng carburetor our gold palladium electrode spark plugs started just like spark-ignited engines should[instantly] and outlived the NGK platinum plugs by a factor of over 10:1.

interesting side note, d-b hated anyone else playing with these engines. the engine that we were allowed to work on would become the last one to run. and it eventually had to be retired because d-b had not provided enough cooling for the engines.

none of what we showed the transit bus operator was ever accepted by d-b. they never altered their incorrect carburetion system, they never altered their horribly inadequate ignition system, they never improved the cooling. they never did anything to make the engines work. this incident taught me much about ego at engine manufacturers. their motto often is, DON'T CONFUSE ME WITH REALITY.
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Old 05-30-2003, 09:03 PM
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Join Date: Mar 2003
Location: Southern California
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The big issue with Merc spark plugs is the fact that they are non-resistor. The responses don't address this issue, but if you add additional resistance to the circuit, it is going to consume some ignition energy (I-squared-R), so the best bet is to use the non-resistor plugs recommended by Mercedes.

Another thing to consider is that the spark plug is "cool" relative to the 4500 degree F flame kernel that is initiated by the spark. All those ground electrodes can act as a heat sink and quench an insipient flame. "High Performance" spark plugs use very fine center and ground electrodes, which minimize the heat sink.

Multiple ground electrode spark plugs are just marketing hype. I know of NO manufacturers who install them as original equipment, and they are looking for every last bit of efficiency as many are on the ragged edge of not making their CAFE numbers and paying big fines. If multiple ground electrode spark plugs had any value, OEMs would install them as original equipment. But they don't. There's a message there!

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Old 05-30-2003, 09:08 PM
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Thank you Albert for taking the time to share this. Very interesting.

I worked for an automobile manufacturer who would not believe there were component failures in cars operated in the U.S. but not also in Germany. Despite numerous high-level meetings the failures were ignored.

Soon after a very well known and high official came to the U.S. for a meeting and vacation. Well readily supplied him with one of the fleet cars. Yes, you probably guessed it ... that particular component failed (could not have planned it better in terms of timing) made him late.

When he called for service assistance he was told those components don't fail! Needless to say all were replaced at no-charge on all models sold in the U.S.

The component failure had to do with electrical loads. The U.S. car were always loaded with options and thus the charging systems were much more stressed than the European counterparts.

'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)
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Old 05-31-2003, 01:05 AM
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ordinarily, i would let duke's comments ride, but he has it so wrong that i am compelled to interject some strands of engineering verities.

i haven't checked out the plugs or high voltage leads from my newer benzes[e320cab, s500c], but my 116[6.9] and my 126's[560sel, 560sec] do have resistance in the secondary circuits. the resistor[4k-7k Ohms] is potted into the spark plug boot.

furthermore, though i haven't examined my distributor rotors lately, years ago, there was a resistor potted into that component.

i dealt with this some weeks ago in a post asking about 1k or 5k ohm resistance.

succinctly, d-b understood that arcing areas needed rfi/emi suppression or attenuation. and by and large, these levels of impedance are negligible in the overall scheme of the inductive ignition systems that were being used.

as to multiple electrode spark plugs, that they are not used as original equipment is basically a matter of cost. automobile manufacturers are going to select the least expensive component. more than a single ground elecrode costs more money. qed.

in the realm of the most difficult spark-ignited engines, severe service, methane-fueled engines that run continuously at elevated bmep's and are most often turbocharged, multiple electrode spark plugs are the most commonly used. they have no performance drawbacks in comparison to a single ground electrode spark plug. they furnish considerably advanced levels of durability.

as an example, a single ground electrode, precious metal-attached plug has been fitted as original equipment for cng-fueled diesel conversions. it will make emissions numbers, but durability is generally limited to less than 20,000 miles. and unpredictably so. a multiple ground electrode plug in the same engine will make the same emissions numbers, but will live predictably for more than 100,00 0 miles.

quite candidly, engine manufacturers do not go to great lengths to evaluate alternatives to the cheapest or most graft-provoking components.
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Old 05-31-2003, 01:31 AM
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Location: Southern California
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Take a good look at the KE fuel system and even the throttle linkage on a Merc and you will realize that these systems are not designed to the lowest cost, and MB doesn't select spark plugs based on the lowest bid, especially when they play a key role in emissions and fuel economy.

The ignition system and spark plug requirments for methane-powered stationary engines that operate at a relatively steady speed and high load are different from automotive gasoline engines that has a much wider range of speed and load.

I stand by my remarks. Multi-ground electrode spark plugs for automobiles are just marketing hype, but the manufacturers looked at the guy making millions on Splitfires before the FTC shut down his deceptive advertising and decided to get on the bandwagon.


Last edited by Duke2.6; 05-31-2003 at 01:38 AM.
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Old 05-31-2003, 01:12 PM
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Location: Ontario, Canada
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Originally posted by Duke2.6

Multiple ground electrode spark plugs are just marketing hype. I know of NO manufacturers who install them as original equipment,

Well, I'll tell you a secret.
The M-B recommended sparkplug for my 2000 C 230 Kompressor is a Bosch F7 KTRC.
Guess what,........the " T " stands for triple electrode.
2007 C 230 Sport.
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Old 05-31-2003, 05:38 PM
I told you so!
Join Date: Jun 2002
Location: Motor City, MI
Posts: 2,741
Albert, thanks for the detailed background on spark plugs. One can learn a lot from design engineers.

I've always taken a file and rounded down the corners of my spark plugs - not the corners facing the center electrode, but the two upper corners and side corners... made it shaped somewhat like the end of a twinkie. I guess I was doing it to focus the charge for the spark and to reduce any unnecessary hot spots on the electrode. Have I been harming anything?
95 E320 Cabriolet, 131K
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Old 05-31-2003, 11:59 PM
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And maybe the moral of the story is one size doesn't necessarily fit all.

I like Manny's reply.
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Old 06-01-2003, 02:18 AM
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duke, still doesn't get it.

though it is true that most methane-fueled engines are constant speed, constant load[driving compressors, generators, pumps], the instance that i cited involved transit bus prime movers.

similar to an automotive application but even more demanding.

i could go further in detailing how an engine manufacturer goes about selecting original equipment components. suffice it to say, i have found that virtually no engine manufacturers have specs and/or qualifying protocols for electrical ignition components. contrast this with the specs and qualifying protocols for compression ignition components which are detailed and written.

lastly, concerning splitfire. you link that to a "guy". if a "guy"is a corporation i guess that will work. but the autolite operations of allied-signal corp manufactured them. and they were marketed by the same outfit that markets prestone anti-freeze. if this is a "guy", i am napoleon.

beam me up scotty.
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Old 06-01-2003, 04:53 PM
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I've used Bosch +4 in my 97 E320 and the main improvment is better startup more cold hesitation. But they don't startup as fast as the old Bosch supers.
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Old 06-01-2003, 05:58 PM
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[QUOTE]Originally posted by royaiii
and the main improvment is better startup performance...But they don't startup as fast

I've read this a few times and don't get it???
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Old 06-01-2003, 09:00 PM
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The initial catch is not as fast as those japanese 4-cylinders but for the first minute or so the car does have better power.
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