SharkSkin

I know you weren't, John -- and you're right, at 3KHz one would think it shouldn't be too critical. No doubt you have the technical background to understand the issues and do the right thing, and I wasn't trying to diminish your remarks either -- my intent was more to let the general DIY'er know that there are some factors they may not be able to measure.

SharkSkin

Rob, Timing is not triggered by the distributors on your car AFAIK, so no.

bigrob

Thanks Dave!

Jim bailey - 928 International

There were a couple batches from 2004-2005 where the molded connector had the wires flip flopped long ago corrected BUT every once in a while one pops up from that batch. It is interesting to me that we admire and respect Porsche design and engineering , love the rarity and exclusivity of the 928 , relish the fact that it is a $100,000 super car ,The Flagship , the very best sports car that Porsche could build from a clean sheet all original no compromise design ......Yet $100 for a "wire" is too much When Porsche decides that this wire is "No Longer Available" and stops making them THEN we have a real problem... and yes the old very brown 1980 got a new green wire a few years ago.

Fabio421

Will a green wire in poor shape cause poor performance but still allow the car to run pretty well? My 78 runs decent but not great like my 84. I noticed that the wire on my 84 is tip top where the one on the 78 is horrible looking and even has some bare wire showing in a couple of spots. Those spots are not contacting anything though.

Jim bailey - 928 International

The very small signal from the distributor which travels inside that wire is the ONLY thing that tells the ignition system WHEN it should fire. False/missing signals can cause ignition timing errors erratic timing and poor performance. It is a VERY important signal on all 78-84 cars.

soontobered84

Who would have thought that this one little question could bring out all the other questions that go along with it? Jim, you guys should be seeing a huge boost in sales of the green wire. Heck, I might just buy a couple myself. Do I get any kind of commission for my effort?

SharkSkin

I thought the 84 Euro was LH, with spark triggered by EZK rather than the dist./green wire... not true? BigRob, if I gave you wrong info I apologize.

Rob, I assume your distributors look like the pic below?

John Speake

84 is a tricky year to define because of difference in engines US to Euro.

So 84 Euro S is twin discributor as per picture, 84 US is single disctributor with green wire.

hacker-pschorr

I'm puzzled by this since after the connector, there is "regular" wire going to the ignition box.

So is the coaxial design for shielding from any possible electrical interference?

SharkSkin

I assume that it is for shielding, yes. That short section of wire that you mention is a good distance from the HT leads, plus it is relatively short. It's been a good 3 years since I had the conversation with DR about the bad batch they had -- probably best to go back to the source for more specific info. Or maybe John Speake has data from the research he was talking about doing?

I imagine that with the signal being no more than 100Hz on that wire, there must be a relatively broad range of acceptable impedance and or capacitance per foot for the wire, but once you get out of that regime the results might be a bit unpredictable. So if you replace with wire that is barely within the acceptable range you might get a miss under certain conditions.

Best bet would be to get some samples and measure them to come up with an average & std. deviation, which it seems John was trying to do. Since the impedance ratings of coax usually mention a reference frequency much higher than this wire ever sees, it might be best to test it and test replacement candidates at the 10-100Hz that it would see in service.

hupp

I currently have a green wire and gauge cluster printed circuit stashed in a very safe place --- for potential future needs.

dr bob

Anybody have a picture of the connectors? Something exotic for cars may be common in communications stuff, for instance.

You can measure the capacitance of the wire, calculate the velocity factor from materials and dimensions if that's really important. I'll guess that the 8x.5xredline_RPM's max signal frequency is no problem for VF, but the capacitance will affect the shape of the signal out the other end. The most likely concern is shielding, ground the shield at source end only for ground loop protection and noise, etc.

Connectors will be a bigger issue for making replacements than the cable will be, I suspect.

ROG100

Hi John,
I sell a lot of the "green wires" for $98.
I would be interested in your alternative.
Roger

hacker-pschorr

That is what caused me to bump this. If the exact length (some have suggested) or other very specific specifications to this wire were really that important. The short piece of "regular" copper cables going from the green wire to the ignition box seams to negate those theories.

It seams to me (just a total guess) the coax style wire is designed to protect against EMI - same reason why the four pairs of wires in CAT5 cable are twisted in different length strands to cause the EMI signals to "miss" each other (if that is the right way to describe it).
This poor cable has to go along the path of four spark plug cables, near the coil cable, lots of other electrical signals floating around etc.... the short section from the green wire to the ignition box is "out of harms way" so the type of cable no longer matters.

This is all 100% theory on my part - no data or testing to back any of this up.

I have an idea up my sleeve, just trying to gather more info. If this works I'll share my findings.