Using platinum or iridium plugs in a waste spark engine is a waste of money. Half the plugs are sparking from the outer to the center electrode.

The mercedes waste spark does not work this way. Spark is actually out to both plugs and maximum current to the plug under compression.

Sure it does. The current flows out the center and across the gap of one spark plug, through the block, and then from the side electrode across the gap to the center of the other plug. It's a big circle.

Chas, I believe you and whipple are both correct. Though the current flows in a big circle across two plugs, 80% of the spark energy is used in the compressed cylinder. It has to do with the difference in environment around the gap.

__________________
95 E320 Cabriolet, 169K

That's not my argument.
One spark plug of the pair will have the spark jumping from side to center electrode every revolution, half of those sparks will happen under compression.

Series circuit on Waste Spark..second plug fires from ground source.
And Plats in a 104 misfire right out of the box...scope one sometimes.

For orig poster..you want to use BP5EFS NGK...plugs.

__________________
A Dalton

Agreed. Just received 12 of these from a chap in the UK. Gapped 6 of them to 0.032" and installed in my 190E yesterday. She purrs like new....

__________________
Neil.


1991 190E 2.6 170k
1995 E320CA 57k
1999 Chevy Tahoe 98k
2000 R1150GS 45k
1983 300CD 178k - sold, but not forgotten

The way I understand the spark cycle of the wasted spark you guys are talking about if on plug is not connected the spark would not occur. Ford for instance if one spark plug is not connected then both do not fire. This is not the case with the mercedes. Either plug will fire with the other disconnected. The spark arcs to ground, which is the engine. Thus there is no way that the spark is coming back from ground into the opposite plug. I have done many a diagnostic on the m104 system. In fact if you create enough gap on one plug to pull more load to that plug the computer will think that the misfire is the wrong cylinder. Thus a bad plug wire can cause a misfire on the opposite cylinder.

what chap was that- I need to get some myself

__________________
'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

Here - http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260334931615&ssPageName=ADME:B:EF:GB:1123

It would be great if Phil could stock these....

__________________
Neil.


1991 190E 2.6 170k
1995 E320CA 57k
1999 Chevy Tahoe 98k
2000 R1150GS 45k
1983 300CD 178k - sold, but not forgotten

were non resiistance leads for the 103 anywhere?

Interesting - I was trying to figure out how this would be possible, and it would indeed depend on a coil producing both positive and negative high voltages. There's no other way to do it. I still don't see how it could be a series circuit the way you described it. There's no incentive for the electrons to travel past the block. They're satisfied at that point.

Arthur Dalton - I think you might have it slightly backwards. In other words, I don't think the spark travels across the block to another plug. There's no electrical incentive for them to do that. They're at ground potential at that point and it makes 'em lazy. Here's what I think is happening, using 10KV for easy math....

1) Compressed cylinder gets +10KV to center electrode. This draws electrons from the block to the center electrode
2) Those electrons have now traveled to the coil on the positively charged spark plug wire, where they become available to go out the negative end of the coil, or not.
3) The electrons travel out the negative end of the coil to the waste spark cylinder's center electrode. Because they are more negative than ground, they travel from the center electrode to the rim, where they meet ground. Circuit complete.

The reason I said "or not" in step two is because in this setup, it would not be necessary for both plugs to work in order to get one to spark, though it might make a difference in spark intensity if one were not. If the coil is producing high voltage in both positive and negative, either form of spark would be satisfied by the ground potential of the battery/chassis.

I think the reason you've got it backwards is because you're not quite correct about polarity. Electrons flow from the negative towards the positive. Therefore, a high positive voltage applied to the center electrode will cause a spark to jump from the edge electrode towards center. The opposite is also true.

Also, I think the "series" part of this circuit is in the coil, not the plugs. The two high voltage + and - taps are inherently in series........

Either way, I don't see high voltage traveling across the block and then across another air gap. Not gonna happen.


-tp

>
Of course it does.

<>

How can they be satisfied at that point...the coil secondary is ISOLATED
from any engine grounds, so it does not get grounded until it completes back to the coil...ISO CIRCUIT. It does not use or need engine ground.


And it is a SERIES circuit...no doubt about it....
Read were I state the secondary is iso from all other circuits....engine ground means NOTHING to DIS waste system. The circuit has to be completed back to the iso winding for any spark to occur.

You want a schematic????

http://www.asashop.org/autoinc/feb97/DIS.htm

< >>
No ..they are not "IN SERIES" ..the secondary winding has a + and - end to the single winding, with a tap on each end ..that does not make it Series or a Series Circuit , it simply makes it a winding with a pos and a neg side,....[ like any other dc coil winding ]...and those taps [ terminals] each feed a plug.. a pos feed for one , and a neg feed for the other...and the base of each screwed into the block... that puts the plugs in SERIES WITH the winding and out of PHASE with each other [ reversed polarity] So , no matter , the completed series circuit requires a spark jump to reach back to the coil. It is a closed loop consisting of 2 plugs and one winding.
The bases of the plug are simply mounted to the block and b/c they are both the threaded portion of the plug, that puts them OUT OF PHASE in the SERIES circuit. The second plug in the series HAS TO fire the opposite polarity than the first...if they fired in the same POLARITY, they would have to be wired in PARELLEL... and if they were in Parellel, then the taps would both have to be the same positive, using the block as negative to complete the circuit...... but they are not the same , they are pos AND neg.......... meaning we have a simple, series circuit..
You will note that my other post states that the coil does not have a CENTER TAP..if it did have one , only then could the coil have TWO pos. outputs, one for each plug..and only then would each plug fire the same polarity b/c the circuit whould then be a PARELLEL circuit.
Look up Waste Spark anywhere and you will see "SERIES CIRCUIT". where the single coil feeds plug 1, on to plug 2 , and back to the coil . ALL ISO and ALL in SERIES circuit.
Here is another one for ya.....pay attention to the engine block being used as a conductor for the seconday series flow..you are correct about the polarity, but not about the series circuit design or the plug phasing...which is the point being made.

http://www.auto-repair-help.com/automotive_maintenance/ignition_coil.php

The above statements are not correct, Arthur Dalton is correct. Its all to do with relative potential, the block would have to be connected to the negative terminal of the coil for it to be "earthed". The block is not earthed relative to the coil as it is in other ignition systems.
It cannot act as an electron sink, thats making it a capacitor!!

Waste spark engine? The M103?

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't