Author Topic: Spark plugs  (Read 8398 times)

bahnstormer109

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Spark plugs
« on: 15 August 2007, 01:06 AM »
Im going to service my 450SEL myself for the first time probably this weekend, or next weekend. Im going to change the oil and filter and the ignition system. theres nothing really wrong with the ignition, but its all looking a bit old. the leads and dizzy cap etc just look old and the contacts in the cap are worn and a bit burnt looking.
im going to get new plugs, leads, cap, rotor and coil.

does anyone know what the "prong" on the business- end of a spark plug is called?? (it must have a proper name)

anyway, ive seen a set of bosch spark plugs with 4 of these "prongs" instead of the usual just one. its supposed to make a stronger more efficient spark. has anyone tried these? any recommendations good or bad?

im thinking of giving them a go to see if the car runs any better. theres nothing wrong with how its running at the moment, only the car gets a bit of a "shiver" sometimes while idling.

cheers,
Paolo.
Paolo,
Brisbane, Australia.

72 300SEL 3.5
84 280CE
86 560SEL
86 230TE

oscar

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Re: Spark plugs
« Reply #1 on: 15 August 2007, 01:38 AM »
Which spark plug?  :o :o Click pic below. 
If you go to the Bosch website there'll be their science behind the Super4 range or whatever the latest is now.  I think the outer electrode is called the cathode and the inner electrode is the anode although Bosch calls 'em ground electrode and centre electrode.

Anyway, quality of spark is one thing.  IMO, the Super 4 type plugs have the ability to last longer compared to a good quality single cathode spark plug and that's it.  And Why?

Only ONE cathode will produce a spark!!!  You' wont get all four "prongs" firing at the same time.  The spark will travel the path of least resistance which can vary between the four and as one shortens or degrades, another one becomes the favourite, offering the shortest path for a spark.

BTW, I haven't tried them, I'm sure they work well and I think styria has real world experience with them.  Personally I think they're unnecessary and doubt they ignite the F/A mixture any more efficiently than a good conventional spark plug. 
I stick with NGK BP6ES plugs.  A big fan of Bosch, for some reason, WR 7's kept leaking a spark even with new leads.

1973 350SE, my first & fave

CraigS

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Re: Spark plugs
« Reply #2 on: 15 August 2007, 01:45 AM »
I think what you are talking about are called Platinum plugs. If you check with the NGK website, the only plug they recommend is the BP6ES - a conventional plug. It might be worth a phone call to NGK.

Based on experience, and others experience, NGK are the preferred plug, not Bosch and definitely not Champion.

Good luck buying new H/T leads, and don't get too much of a shock when you buy them - assuming you are going to buy the correct ones with the proper resistance ends. Don't get suckered into what the parts books say at the parts shop. They are generally NOT correct.

These are what the correct ones look like. These are from Beru. The core wire should be copper, not carbon.

« Last Edit: 15 August 2007, 01:47 AM by CraigS »

bahnstormer109

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Re: Spark plugs
« Reply #3 on: 15 August 2007, 03:26 AM »
Hi Craig,

my 450 has beru leads on it, apparently theyre the original spec leads to use. my 3.5 and my mates 280S have bosch leads.

we actually just replaced the leads on the 280S with bosch leads from an auto parts store down the road and theyve been fine. they cost $60, this included an extra charge to special order them in because they didnt have any in stock.

they have a set in stock at the moment for the 350/450. they also have a range of bosch caps, rotors, coils etc, though i think ones to suit benzes will need to be ordered in.

i was impressed with the leads we put on the 280S, they come with a 5 year warranty and the ends that attach to the spark plugs are 1 piece rubber covered, not the hard plastic or metal that other leads have that come loose and break apart. im going to chuck a set of these on my V8s and see how they go. the beru type just seem to get loose at the ends where the lead attaches to the suppressor. on the 280S you could actually see sparks leaking out of this join. the bosch ones are nicely sealed up, one piece units.
the car had a bad misfire that made it virtually undriveable, and it just purrs now.
« Last Edit: 15 August 2007, 03:30 AM by bahnstormer109 »
Paolo,
Brisbane, Australia.

72 300SEL 3.5
84 280CE
86 560SEL
86 230TE

BC

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Re: Spark plugs
« Reply #4 on: 15 August 2007, 04:58 AM »
Paolo - the plug with the 4 electrode system is the Bosch Super 4. They are like the old Golden Lodge plugs of years ago. The Golden Lodge had the same arrangement and YES it did work. The Super 4 is not Platinum and it's worth a try, depending on cost. I used Golden Lodge in my Alfa 164 and also in the Mazda 13B and they worked better than the standard Bosch or NGK.
My understanding is that that they foul less easily from lots of starting and short trips so they may well be worth trying.
Craig - is the NGK better? I have always used the Bosch in the 450 and not tried the NGK - should I change to NGK?
Good luck - I think we are all interested in the results.
Regards,
BC
« Last Edit: 15 August 2007, 09:30 AM by Brian Crump »
1979 450SE. Silvergreen/Ivory leather. For sale.
2001 ML320. Titanite Red/Java leather.
2007 CLK350. Cubanite/Pebble Beige Leather.
1993 Silver Spirit II. Dark Oyster/Parchment Leather.

s class

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Re: Spark plugs
« Reply #5 on: 15 August 2007, 12:47 PM »
Paolo,

As others have suggested, cheap spares shop leads will cause you a lot of hassles.  The supressors in the correct spec leads do 2 things :

a) suppress RF (radio) noise
b) control the speed of the spark

b) is important.  The correct leads we should use have a built-in designed impedance (~resistance) of a few kilo-ohms.  THis provides damping on the spark propagation to get a more steady, complete burn of the mixture. 

Ryan

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

bahnstormer109

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Re: Spark plugs
« Reply #6 on: 15 August 2007, 02:32 PM »
Hi Ryan,

i understand what you mean, and youre right. cost isnt an issue here as im looking at $80 for spark plugs! i just think these leads are better than the beru brand for reasons i mentioned before, the beru leads just fall apart!
these are bosch after all, the same brand that the rest of the electrics on the car are. id rather use bosch plugs and leads with bosch dist cap and coil, rather then mixing and matching NGK plus, with beru leads and the bosch cap and coil etc for example. thats where problems will start as the products wont be well integrated and suited to each other. doesnt really make sense.

will let you all know how they go i suppose!

cheers,
Paolo.
Paolo,
Brisbane, Australia.

72 300SEL 3.5
84 280CE
86 560SEL
86 230TE

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Re: Spark plugs
« Reply #7 on: 16 August 2007, 03:42 AM »
Before I changed my plugs I looked into the multi-electrode variety and was reccommended by Bosch NOT to use them. The single electrode is EXACTLY what is specified. the multi-variety are for modern ignition systems.
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s class

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Re: Spark plugs
« Reply #8 on: 16 August 2007, 02:18 PM »
styria,

the units of resistance are 'ohms' The symbol is a Greek 'omega' sign - the one that looks like a curly 'n' with feet.  I don't know how to get the symbol here.....  One ohm is a very small amount though, so one normally works in 'kilo-ohms'.  1 kilo-ohm, abbreviated as 1k-ohmssymbol- is equal to 1000 ohms.

As far as I know, the M110 and M117 also use 5kohm supressors.  The M119 in my S500 has 2.5kohm supressors. 

As to their necessity or otherwise, due to some ignition lead failures, my M110 currently has a mixture of the correct 5k leads on some cylinders, and some non-impadanced spares-shop jobbies on the others.  THis will soon be rectified - there is a new set of bosch leads on its way to me as we speak....

With this current setup the idle is lumpy and uneven - as one might expect due to the different combustion characteristics. 

I will try to explain it with an analogy to water in a tank.

Think about a tank of water sitting up at roof height.  SUppose it has a hose leading out the bottom.  If the hose is fat, the water in the tank will drain out in one sudden rush.  The flow will have a HIGH FLOW RATE, but SHORT FLOW DURATION.  NOw replace the hose with a much thinner one.  We will have a SLOWER FLOW RATE, with LONG FLOW DURATION.

now the analogy

water tank systemequivalent to :      ignition system
quantity of water to dischargeequivalent to :      quantity of electricity or charge, or 'spark' to be delivered to the cylinder
size of discharge pipeequivalent to :      ignition lead impedance
large pipe diameter equals low impediment to flow   equivalent to :      low supressor impedance
small pipe diameter equals high impediment to flow   equivalent to :      high supressor impedance

So in English, if we have a low impedance spares shop ignition lead, this is like the fat pipe on the water tank.  All our electrical 'spark' will flow very quickly, and act over a very short time period

If install a proper supressor, the higher impedance will result in THE SAME AMOUNT OF SPARK, or electrical energy, being delivered more slowly - hopefully matching the speed of fuel mixture propagation. 

The idea is that the combustion process and gas flow takes a little time, so by slowing the spark, it is possible to get the spark to 'last longer' and be present for a much larger portion of the gas combustion process.  THis will lead to more complete mixture burning. 

It's late, I'm tired, if this makes no sense, let me know and I'll try again. 

Ryan
« Last Edit: 16 August 2007, 02:24 PM by s class »

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

Bandolero

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Re: Spark plugs
« Reply #9 on: 16 August 2007, 03:41 PM »
My 280SE uses 1K ohm plug connectors.
The 450 uses 4k ohm connectors & the 6.9 uses 5k ohm connectors.

Russell Bond - (Adelaide, South Australia)
1978 450SEL 6.9 .... #5166 .... 12/78 (Sold.) www.ezycoat.com.au

s class

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Re: Spark plugs
« Reply #10 on: 16 August 2007, 03:57 PM »
Russel, I'm willing to accept that.  Truth be told, I actually can't remember what my 450 has, and as to the 280, well its a motley assortment of old leads, so its quite probable none of them are the correct ones.  I'll see what I get when my autohaus parcel arrives.

Ryan

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

BC

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Re: Spark plugs
« Reply #11 on: 16 August 2007, 03:59 PM »
So what would be the result of having the wrong leads? Apart from miss firing etc?
Regards,
BC
1979 450SE. Silvergreen/Ivory leather. For sale.
2001 ML320. Titanite Red/Java leather.
2007 CLK350. Cubanite/Pebble Beige Leather.
1993 Silver Spirit II. Dark Oyster/Parchment Leather.

Bandolero

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Re: Spark plugs
« Reply #12 on: 16 August 2007, 04:15 PM »
Well, I had some aftermarket leads on my 280 and then I put some new Bosch leads that had the correct ohm connectors and I didn't notice any difference.
Still has the exact same power going up Mt Barker road. Can only do 98 kph up the hill (100 zone) unless I change down to 3rd, then it revs out to over 120 kph.
So I give up.....I don't know if there is any difference so long as you use good aftermarket leads.....I dunno.... ??? ???
Russell Bond - (Adelaide, South Australia)
1978 450SEL 6.9 .... #5166 .... 12/78 (Sold.) www.ezycoat.com.au

BC

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Re: Spark plugs
« Reply #13 on: 16 August 2007, 04:28 PM »
When I bought my 450 I threw out the old leads and had a set of super duper Magnecor leads made up and the car ran like a truck. On the 'scope the leads were all over the place so it was back to the originals and all is good. The leads I had made were the correct impedance - or supposedly so - and a waste of money. I had previously used them on various engines and they were great... ???
Beats me.
Regards,
BC
1979 450SE. Silvergreen/Ivory leather. For sale.
2001 ML320. Titanite Red/Java leather.
2007 CLK350. Cubanite/Pebble Beige Leather.
1993 Silver Spirit II. Dark Oyster/Parchment Leather.

bahnstormer109

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Re: Spark plugs
« Reply #14 on: 17 August 2007, 01:34 AM »
Well ive had words with my mechanic and hes told me not to change the leads or the coil full stop. he told me to bring it in and he will put it on a machine and change any suppressors if required. he said the Bosch Super 4 plugs are good and a new cap and rotor is all i should do and to leave everything else alone.

so thats what im going to do.

and im going to change the oil with Penrite 20W-60.

and she should be sweet for another 5000km.

my mechanic said that if i put the new bosch leads on id probably have to change them every couple of years and although theyre cheaper its a false economy.
i said "every 2 years?? thats cool, i was prepared to change them every year!" 

though i didnt say aloud that i was thinking: "$60 for new leads every 2 years is still going to be cheaper than bringing it into the workshop to have you put it on a machine and check each individual lead and change a couple of supressors every 2 years!".   ::)

anyway, we've compromised.
Paolo,
Brisbane, Australia.

72 300SEL 3.5
84 280CE
86 560SEL
86 230TE