That makes sense, but as far as I know, there is no "alternative" set of wires for 103 systems that work with Bosch's new "R" plug? I supppose there could also be a need for a redesigned dist. cap & rotor?

If anyone knows of a new set of wires being offered for 103 motors that will be compatible with the new Bosch "R" plug, do let us know.

I ordered from there.. but the resistor plugs came instead. If you still haven't recieved your plugs, you'll notice the labeling when you get it.

I'm not the only one that recieved it either.

...from my NGK catalog. My Cosworth Vega uses the same plug as M103, but a resistor type. I use the TR5 in my CV - just bought new set - on sale at Pep Boys.

The kid didn't understand what "TR5" meant - not on the computer, so I asked him if he had a paper catalog (I didn't bring mine). He did - so I looked up the four digit stock number for a box of four - 2238 I think it was.

Then he was able to order them.

It's just pathetic!

Duke

<<The kid didn't understand what "TR5" meant - not on the computer,
It's just pathetic! >>>



" Fries with that ???? "

I don't know how bad resistor vs non-resistor plugs would be. Bosch doesn't think it would be a problem, and I can't beleive that they would recommend a misapplication of one of their products, resulting in poor performance and a bad reputation for them. That being said, the service manual for an 86 560SL (probably the same technology as most other MB's of that era) says the following:

- The load at the high voltage end of the system must be at least 2K - the wires= 1K and the distributor cap (surprise!) = 1K. Damage to the ECU (EZL) could otherwise result.

-Don't install a 5K resistance rotor


So:
<2K resistance, bad.
2K resistance, good.
7K resistance (1+1+5)=bad, probably not enough spark.

So ignition coil to dist cap (0 ohms) (I checked, it is NOT a resistance wire)+distributor cap (1K ohms)+wire from dist to plug (1K) +0K non-resistor wires = 2K, as per the manual.

So, I SUPPOSE that it would be possible to install a 1K plug (my Bosch resistor plugs come in at ~1K), no resistance wires, and get nearly exactly the same running results from the same 2K load (although there MAY be an effect on the waveform of the spark, would actually have to look at an oscilloscope).

But, here's the problem with the above. Ignition wires generally fail by leaking and arcing to grounded metal (the engine, some part of an accessory, etc). I've always seen the distributor to plug wires fail before the ignition coil to distributor wire.

With no-resistor wires, a shorted distributor cap to plug wire would result in ONLY a 1K resistance to the grounded plug, beyond the original specs and possibly resulting in overloading/overheating/damaging the output transistor of the ECU, which is a pretty expensive part. It might not be good for the coil either.

My conclusions (not backed up by oscilloscope waveforms, voltage readings, RF spectrum analyzer, etc):

1. Use of a resistor plug in a system designed for non-resistor plugs will add 50% total resistance per circuit, not good, but probably OK if you can deal with the plugs becoming marginal with age-related wear sooner - you might have to change them more often or gap them a little more tightly to start with)

2. Use of resistor plugs and non-resistor wires would probably work, but could POSSIBLY result in expensive damage to the ECU should the wires fail (which they certainly eventually will do unless proactively replaced). It MAY also result in increased RF and radio interference.

On the other hand, if the resistor in resistor wires is in the shell of the spark plug "socket" then this concern may not exist, because a shorted "resistor" wire and a shorted "non-resistor" wire would present the same resistance to the coil - the 1K of the distributor cap only.

Does anyone get this?

PS: I was lucky enough to get the last 8 Bosch non-resistor plugs NAPA had locally in addition to the 8 non-resistor plugs I got. They checked their inventory and I got the last 8 within a 30-mi radius, apparently (and by accident, I picked the right store). But they were all at a good price (like, $1.20 ea). Bottom line, looks like we'll be using resistor plugs in the future...

non-resistor plug sourcing
 

There must be some out there still. Anyone know anyone who sources hard to find parts for a living? There has to be plenty left for us to hoard. I could use a set right now. Will buy a few sets when I find them.

Jason

..as Strife, I ave always had good luck finding Bosch Coppers at NAPA stores

Here's a guy in Canada with H9DC plugs listed on EBay, but he has a minimum $50.00 order. That would be $.50/plug, so anyone interested in a bulk buy?http://cgi.ebay.com/ebaymotors/BOSCH-PLATINUM-SPARK-PLUGS-SUPER-BOSCH_W0QQcmdZViewItemQQcategoryZ33693QQihZ019QQitemZ8052274663QQrdZ1QQsspagenameZWD1V

I've started picking up the Beru copper equivelents.. I have two sets for my m117's coming up from the warehouse...Hope to try some out shortly and I'll report back.

I've pulled Many resistor plugs from MB's (most often V8's) to find that installing a proper non-resistor plug solved their idling issue.

Jonathan

I've emailed arizona ********... to see if they will be sending me Bosch non-resistors for my w124's...

i ordered 12 yesterday...

As a follow-up to my previous post, the resistance of Bosch W9RDC plugs in my hands is 6K. Considering that the 107 MB manual SPECIFICALLY cautions against using a 5K resistance rotor, it seems that resistor plugs are BAD in this engine with the stock ignition system.

Nice to know!!!! Thanks:)

Jonathan

Warren at Kingsborne checked into the Beru plugs a couple weeks ago for me. He said they were coming out with a new non-resistor plug in October that would be a direct substitute for the Bosch plug. He said it would be part # Z240.

In his contacts with Beru and whoever he spoke to in Germany, they told him that you should absolutely NOT use a resistor type plug in the M103 ignition system.

I hope Phil will look into this and become a mass distributor of the new plugs.

NGK has been my first choice for thirty years and the choice of most MB mechanics here in Ca. My mechanics and I have installed thousands of them and never had a problem. I prefer them to Bosch and will pay the extra money if Bosch is cheaper. As I've stated in many oil threads, I don't give a rats ass what brand of oil I put in my cars as long as it's a name brand and it'e the cheapest, but I am particular about my spark plugs.