Bosch Spark Plug Wires

[al_lieffring]

I don't doubt that Joe or Dan have seen these sets made with carbon wires, but the set I bought from Bud's Benz last summer have "Copper Core" wires, I even pulled back the boot on the distributor end to look at the cable, and there was indeed metalic wire, the copper seems to be nickel plated for corrosion resistance.

Now If I could find 4 other people with these same wires that would want to split the cost of  buying another set to replace the 90deg resistor on the #1 cable

Al Lieffring
66 230Sl
Jones'n for a new gas tank

[jameshoward]

Al,

Are you really thinking about buying a new set just to get the straight connector for cyl no 1? You should be able to pick up a beru 1k ohm plug socket at your local dealer. As you know, they just unscrew the 90 degree socket thing and screw in the new plug socket and away you go. If you need one of these and really can't get one, I think I could get one here and send it to you. They don't cost much. Let me know.

If I've got this all muddled up and have missed your point, ignore me.

Incidentally, SLS now only sell the wires set with the 5k ohm ends. They cost 90 euros at set, which is about that in $ or about GBP60. They insist that 5k ohms is correct for the 113.

JH

[Raymond]

"They insist that 5k ohms is correct for the 113"  They would be wrong.
At least partly. 5k-ohms may be correct for '71s but there is plenty of evidence on this site to prove that no resistance would be best for the earlier cars.  For the '68 you want the low resistance plastic connectors.  You want copper core for low resistance.  You want straight connectors with no resistance added, you want plugs that aren't resistors.  In short you want as much wallop from the coil as you can get.

By the way, improperly posting photos can cause the text window on this forum to stretch out.

Ray
'68 280SL 4-spd Coupe

[ja17]

Hello,

Early 280SLs and earlier W113 cars without the factory transistorized ignition used the 1,000 ohm plastic spark plug connectors. Later 280 SLs with the factory transistorized ignition had a much more intense spark so they used the 5,000 ohm metal shielded spark plug connectors.

If you have upgraded your ignition system with a hotter coil or modern ignition, the 5,000 ohm ends work just fine on even the earlier cars. Using the 5,000 ohm resistors on the original early non-transistorized ignitions is a strain on the system.

Joe Alexander
Blacklick, Ohio

[Mike Hughes]

Would the "strain on the system" when using 5000 ohm metal resistors on an otherwise stock early system manifest itself in rapidly pitted points, etc.?

quote:Originally posted by ja17

Early 280SLs and earlier W113 cars without the factory transistorized ignition used the 1,000 ohm plastic spark plug connectors. Later 280 SLs with the factory transistorized ignition had a much more intense spark so they used the 5,000 ohm metal shielded spark plug connectors.

If you have upgraded your ignition system with a hotter coil or modern ignition, the 5,000 ohm ends work just fine on even the earlier cars. Using the 5,000 ohm resistors on the original early non-transistorized ignitions is a strain on the system.

Joe Alexander
Blacklick, Ohio

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[ja17]

Hello Mike,

The points are actually on a different low voltage "primary" circuit. The points should not be effected. The high voltage to the spark plugs on the non-transistorised cars comes from the high voltage terminal (center) of the coil. The high voltage current flows through the coil wire and any rssistor ends on this wire, through the distributor cap, through the rotor and it's internal resistor, back through the distributor cap, through the spark plug wire ends at the distributor with it's resistor, through the spark plug wire, through the spark plug connector and it's resistor, into the spark plug (hopefully non-resistor) and finally the spark!  
Any weak link along the way adds resistance. With the metal shielded spark plug wire ends you start off with 5,000 ohms resistance, you have a resistance built in the rotor (5,000 ohms), and you also have resistance built in some of the wire ends at the distributor in most cases (1,000 ohms). Now if you have the wrong spark plug connectors, or carbon spark plug wire, resistor spark plugs (5,000 ohms),or any other weak failing resistor in the system you have too much resistance and the spark intesity will suffer or fail completely.
Say you have the original early (non-transistorized) ignition system. You should start to be concerned when the total resistance in a single spark plug circuit exceeds 13,000 ohms total from the coil through the spark plug.  So we can compute; coil wire ends (two) 2,000 ohms, rotor 5,000 ohms, distributor end of plug wire 1,000 ohms, and the wrong spark plug connector 5,000 ohms, then you add some resitor spark plugs at another 5,000 ohms!!  You now have a total 18,000 ohms with all new parts, and are over specs to start with! The resistance in many of the parts will increase with age also. The electricity will follow the path of least resistance. So when the resistance becomes to high the spark will simply jump out of the circuit (arcing) or not make it at all causing a miss.


Joe Alexander
Blacklick, Ohio

[Mike Hughes]

So would the extra resistance introduced when using the 5000 ohm metal connectors instead of the 1000 ohm plastic ones cause a weak enough spark to make the plugs foul when they otherwise would not?

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[ja17]

Hello Mike,

If your coil or ignition system has been upgraded with a "hotter" set up the 5,000 ohm ends are no problem.

Most likely the 5,000 ohm  ends will work fine on an original early set-up also. However, you are starting out with a disadvantage which may bring on problems sooner.
Complete failure may not happen until much higher resistance, but issues like hard starting, (especially in damp weather), spark plug fouling, and spark arcing through wire insulation may occur sooner.

If you have carbon spark plug wires, instead of solid copper,  you are adding much more resistance also. As mentioned, resistor spark plugs will add another 5,000 ohms resistance.

Each spark plug wire should be checked with an ohm meter during a tune-up or as needed. This will tell you the condition of the spark plug wires and the resistor ends.

Joe Alexander
Blacklick, Ohio

[J. Huber]

Resurrecting this one... and it all makes sense (sort of) but I wanted to be sure. For a lot of years I have been using "Bosch 7mm Opti-layer copper core Ultra premium " wires. The ends are 1K ohm except the the first one that is the 90 degree 5K.

It is my understanding that I can just change out the 5K (0 356 351 027) for a straight 1K (0 356 301 022). And that the ends screw on. Does this sound right? Do you suppose this will affect the running of the car in anyway?

[bosch red coil, 1.8 ballast resistor, NGK BP5ES plugs]

thanks as always

[jameshoward]

James,

Yes, you can. It's what I did after reading this post.

I went to my auto parts supplier and purchased a new end made by Beru (subsequently edited to provide the correct manufacturer's name after Graphic's post; they are very widely available in Europe; not sure about the US)  that just screwed onto the wire. I checked the readings thereafter and it was exactly the same as the others. Took all of 5 minutes.

James

[J. Huber]

Thanks James, I plan to try the new straight connector soon. Let's see...5 minutes for you = hmm. Ok I'll plan for an hour...

[graphic66]

Anybody ever find a source for Beru wire and ends.

[66andBlue]

Try Kingsborne - very knowledgeable including older parts.
http://www.kingsborne.com/connectors.htm

[waqas]

Anybody ever find a source for Beru wire and ends.

Have you checked with Dan Caron (Dr Benz)?  At some point, he had pre-made sets available in both Bosch and Beru.

[Benz Dr.]

Thanks Wagas, I still can get those wire sets.

This is what you should use based on my recommendations:

26 KV red coil on early systems
1.8 ohm ballast resistor
coil wire without any resistors
new rotor if it has more than 5 K ohms resistance
spark plug wire with no resistors at the distributor cap and 1 K ohms at the spark plug
Bosch W9DCo or similar plug. W7DC is too cold for most engines even though that's the rated plug.

On later ( original ) CD ignition systems I would use the same parts but would leave the coil and any ballast resistors in stock trim. Plug wires don't need the resistor ends on them and you defiantly don't want resistors on the coil wire. I like the same 1 K ohm ends at the plug wires which should have metal ends to be correct. The earlier bakelight ends will also work.

Some of the replacement electronic system instructions indicate that you can remove the ballast resistor. Read the instructions carefully or contact the supplier/manufacturer before you do. The ballast resistor protects the coil from over heating when you leave the key on and the car isn't running. The coil and ballast resistor can and will get very hot even when the engine is running.

[graphic66]

 Dan, How long can you leave they key on without the engine running and not damage the coil or points on your setup. I am very hesitant to play my radio without the car running as my 230SL doesn't have an accessory position. The old radios sound very good at outdoor picnics and such but I am afraid to play it for fear of damaging my coil and points..

[zoegrlh]

A year ago I bought two sets of the Bosch wires in order to have all stright ends and proper restistance for all 6 wires.  They work well, and look good, and have Bosch stamped along the wire for that dressed-up look.
Bob