We have been discussing this in the SL forum.

What I found, was that the original wires on our '72 SL had resistors built into the end that plugs into the distributor cap. These are not removable ends, so I cut one apart and found a 1.6 kohm resistor inside. The total resistance of the wire from end to end was 8 kohm.

I bought a set of Bosch Premium Wires (Opti-Layer Mag wires). These have brass or copper metal ends connected directly to the wire and no apparent built in resistors. I measure these at 1.6 kohms end to end.

It would seem that using resistor plugs with the new wires would probably not increase the overall resistance of the wire/plug combination. (But, I don't know the resistance of a Bosch 7500 WR7DC+ plug. Maybe someone could measure one? - Mine are installed!

I'd like to know if the new Bosch opti wires don't have any resistance built into them or the connector.

If you change the wires are you then screwed?

My engine has a label on front valve cover

Says
Bosch W 7D
Beru M 7D (could be W too hard to see
Champion N9Y

I got NGK in what turns out to equiv to the hotter Bosch W 8D

NGK5BPES
Which I have been told is better for a 200K engine....I hope
the new wires don;t screw up anything

Resisitance seems it could increase with length
but don't know if the 4 inches in wires would make a significant difference.

I have forgotten my electrical E=IR

I'm trying to stick w orig type plug
then they go ahead & change the wires...

Are the Bosch Premium solid core wires?

I got a set of them wires paired with non resisitor NGK plugs ready to go in



Label also has other info with an electrical zap mark by it

Wonder what it is...timing?

25' to 3000

16 +or-3

600 to 758

1 to 2 % CO

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83 500 SEC Euro 198K

Bosch describe the Premium wire sets as having Mag core conductors, which is apparently spiral wound nickel alloy (Elsewhere it says stainless steel). Obviously not copper. I read somewhere that the Premium Supreme have copper cores.

I was surprised to find this out myself having not researched this before I purchased!
But, these the Opti-Layer wires (09027) are recommended for my car in this guide:
http://www.thebestsyntheticoil.com/pdf/SparkPlugs&WiresGuide.pdf

I would like to have bought copper core wires with resistors built in as per originals. But now I have these wires, I think it may be just as well that I have resistor plugs?

In your case, not sure what it does to ECU and plugs if wire/plug combined resistance is lower than designers intended.

Copper is a great conductor

I would hope bosch would research it & make a suitable conducting wire.
magnesium?
not sure how the nickel will effect it
Stainless
arrgh

Thats a dilenma

I bought the bosch wires to try to keep the orig set up as I have a new bosch dis cap & rotor

thought they should be made to go together

Will have to discuss the plugs with the shop
maybe there being a lil hotter will help but it also says delievers the hottest longest spark so maybe a cooler plug?


I certainly don't want to change my old wires & end up running worse

Its running fine
but I think these wires I have are really old & wanted to get new.
Least I got the bumbs half price
Still don't want to waste money...

Beru is supposed to be better?
wonder if they have similar

Gives you a lifetime guarantee.\

http://www.boschautoparts.com/Products/SparkPlugWireSets/

Is that cause they don't think the car will last a lifetime so why worry about offering the guarantee...

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83 500 SEC Euro 198K

Just reading the small print on the side of the Bosch Premium Wires box.

It says Stainless Steel Mag winding(*) for a hotter more powerful and longer spark.

* - The footnote says For American and Asian makes only.

Question I have is, do the 09027 wires which are marked as being for Mercedes Benz 8 cyl Engine have s/s or copper wire?

How do we find that out?

I will ask Arizona ******** (where I bought the parts). I have also emailed Bosch Canada, but not sure I will get much from them.

The pix looks like a bonded steel/copper wire

I think we are confising resistors w resistance.
All electricity when it travels thru a wire will find some resistance as its not flowing thru a vacuum.

I read copper solid core has alot of resistance
but the reason they went away from it is the conductivity of copper
makes alot of interference with the critical computer controlled parts

either that or its an excuse to make with cheaper parts.

Resisitance in a wire is not good
the more resistance the harder the electric has to worl to get thru the wire. these days there is so much inital voltage going thru that unless you have bad leakling wires you will have enough to jump the gap at the plug

Another point I read was that the resulting voltage that jumps the gap
will only be the amount necessary yo make the jump
hopefully its about 10,000 but could be up to 30,000

So maybe the wires are ok

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83 500 SEC Euro 198K

Camelot,
After going through the same exercise as you, I think that I now a slightly better understanding!

MB wanted all wires to have the same resistance and at same time prevent interference with the radio and electronic engine components.

What they did, was use a very low resistance wire (stranded copper), and then they added a resistor at each end in the caps. My old wires measure 8kohms from end to end, the two reisistors are 1.6 and 6 kohms for 7.6 total, so wire is about 0.4 kohms for total of 8 kohms. (Using my old multimeter).

If new Bosch spiral wound wires are used, the wires them selves will have a resistance. I measured mine at 1.6 kohms end to end. If non-resistor plugs are used, this would mean your total resistance would be 1.6 kohms and it would change with length - Difference could be as much as 20%. If you use resistor plugs with say 5kohms resistance, then the affect of the differing wire lengths would only be about 5%. So, it seems to me that it would be advisable to use resistor plugs with wires that do not have built in resistors.

BUT, to add to the confusion, Bosch say this on their site:

Not with Bosch Premium Wire Sets. Electromagnetic interference (EMI), also called radio frequency interference (RFI) is caused whenever a current flows through a wire. This current creates a magnetic field that can disrupt other sensitive electronic components such as the engines electronic control unit or radio. For Japanese and domestic applications, Bosch wire sets have a RFI absorbent shielding material to eliminate interference. In European applications, a solid copper core wire is used with OEM-style resistor connectors that absorb unwanted EMI.

The Bosch Premium Wire Set box says it is for MB V-8 engine, but the wires do not appear to have built in resistors and a resistance check confirms this.

I called Bosch, but just got the run around - the guy was not knowledgeable and just wanted to get me off the phone. Bosch Canada did not respond!

It would be nice to put this subject to bed. But without cooperation from Bosch, that won't happen!

I wish I had bought the Beru wires. Their website provides extensive info on their wires and plugs:

For example: http://www.beru.com/download/produkte/endverbraucher_zt_e.pdf

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

resistance of the wire is the same at any given point
but the longer it travels the slower it will become
So as the lengths vary a bit
I suppose what they did was to add a compensation factor to the end of the shorter ones so that the energy would travel at the same speed even though some had a longer distance to travel

Now that does make sense to me...
as you want to fire the plugs at the appropriate times wo the travel time lag which I don't thinkin a few inches is alot
but its good to have it compensated for

I measured the bosch wires
they were not exactly the same as the MB

Yeah would like to see what Bosch is doing
but it seems like they are not adding that compensation factor to bring the end voltage at the same time in all the wire lengths



I think what really matters is that the end resistance in all the lengths be the same.
You didn't measure each one did you?

That would interest me

I'm thinking the most important thing here is the timing as you want to ge that spark thru to each plug at exact same time wo additional delay from extra resistance caused by longer travel length.

The way I understand it the plug should be able to handle the resulting voltage & only as much that iis necessary willbe used to jump the gap

The equation is
E=IR

I is current
R is resistance
E is voltage

I don't see a factor for distance etc length of wire
but it has to comeinto play
I think?????

current is in sense s time distance factor
as its what moves thru the wire
& its speed is affected by the resisitance of the wire
Maybe resistance is not cumulative?

Its been a lone time since I took physics & electrical courses

LOL

HELP

Where r the electrical gerus'

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83 500 SEC Euro 198K