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Green distributor wire: used on pre-1978 930s?

Was the green distributor signal wire to the CDI used on pre-1978 930s? I have a slightly different black wire with the same connector on my '77 930, except the connector is brownish. It is giving me trouble and wanted to replace it but couldn't figure out if part 930-602-907-01 was the correct one since everywhere I look it states 1978 and later.
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Old 01-25-2014, 06:16 AM
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Yep. I replaced my original dizzy wire with a green one on my 1981 930.
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Old 01-25-2014, 07:19 AM
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green wire

My 1976 930 also has the green distributor wire. I think it should work for you.

Rahl
Old 01-25-2014, 08:09 AM
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The one for a 928 is longer and may fit better for you.
Old 01-25-2014, 08:16 AM
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I must have dyslexia. I thought you were asking about pre 87. Duh
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Old 01-25-2014, 09:08 AM
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For the clockwise rotating (CW) distributors in the 76 and 77 turbos won't the two pins in the connector on a green wire meant for the 78/79 (CCW) need to swap positions?
Old 11-09-2016, 02:56 AM
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Note what JohnOllen said- this is a BIG ISSUE that has mainly been ignored because Porsche dropped the ball and published incorrect information suggesting that the later green wire is a replacement. It is not. The CW vs CCW distributors change everything. With the 3.0 you will SUFFER if you use that green wire. It will alter your timing considerably. Make sure you get the correct wire or wonder why your car runs so poorly.
Old 11-09-2016, 03:28 PM
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Quote:
Originally Posted by alwaysflat6s View Post
Note what JohnOllen said- this is a BIG ISSUE that has mainly been ignored because Porsche dropped the ball and published incorrect information suggesting that the later green wire is a replacement. It is not. The CW vs CCW distributors change everything. With the 3.0 you will SUFFER if you use that green wire. It will alter your timing considerably. Make sure you get the correct wire or wonder why your car runs so poorly.
Can you elaborate? I have been running a green wire in my 77 since 2002. As far as I know, my car has always run the same configuration. How do I go about getting the "correct" wire?
Old 11-10-2016, 03:04 AM
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Mighty Meatlocker Turbo
 
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The distributor wire is a simple, coaxial design - the inner core goes to one pin in the distributor plug, the outer (ground) goes to the other, and then those go to the appropriate pins on the CDI - how does reversing the distributor rotor rotation have any bearing on this?
Old 11-10-2016, 08:39 AM
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For the longest time Porsche didn't explain the difference and when they ran out of the early parts didn't bother producing new ones. I found a supply, replaced mine and got a couple of spares. BTW, there never was a brown wire. That is what HEAT does to these when they stick the distributor directly above the turbocharger with only a thin layer of metal between them. If your wire has the color burned out of it, you absolutely want to check your distributor. This isn't rocket science. Just see if it still rotates smoothly and if your vacuum units function. It's also a good idea to lube things while you are at it..

I asked my brother for better specifics. He is semi-retired 930 specialist. He has educated me about 930 technicals and still writes monthly tech articles for PCA Orange Coast Region Pandemonium magazine. He quickly dug up a tech feature he wrote a while back. They now have a simple adapter that makes it simple for 3.0 930 owners.
Here is his information:


This is so simple I am surprised at the basic misunderstanding on these
I did may article on this a long time ago

Number one;
1. the 1975 (&1974 1977)-911 Turbo was the first production (911) to use a magnetic pulse ignition distributor instead of the old ancient breaker points!

a.The ignition signal is from a permanent magnetic inside the distributor.

b. As the 3.0 Liter distributor rotates it's 6 finger "star wheel" interrupts the magnet's signal and that is the firing point signal to the CDI box, and transformer (coil).

c. Because this magnetic signal is so weak the wire carrying the signal is wrapped with a wire mesh shielding to protect the signal from electrical interference, like the High/Tension spark plug cables!


d. The signal wire is a molded, 2 wire connection, mounted on the side of the distributor

d. The early 3.0L Turbo used a distributor that turns "CW" (Clock Wise) as Porsche has done since 1964.


e. The Signal Wire is replaceable as it is exposed to heat from the turbocharger and exhaust system under the metal sheet
The early 3.0L Turbo C.W. Signal Wire is BLUE in color: Nr. 930.602.911.00


f. The 1978 3.3L Turbo and the 1978- 911 SC used a more sophisticated ignition distributor with a vacuum and boost control that was adapted from the earlier 911 engines.
HOWEVER for the existing parts to be usable for the 911SC and 911 Turbo the Distributor was made to rotate C.C.W. (Counter-Clock Wise), thus the magnetic signal was reversed and therefore had a new GREEN SIGNAL LINE with a reversed connection inside the molded connection on the distributor. GREEN SIGNAL LINE Nr. 930.602.907.01

g. When the Blue signal lines worn out, burned, cracked etc etc. some supplies of blue signal lines ran out and no replacements were available…………
The Green Signal Line can be used on a CW rotating distributor by reversing the two wires going into the CDI box.
And there is an adapter kit supplied by Bosch, Porsche, and wholesale suppliers like SSF.
I use these and then paint the green signal wire with a BLUE stripe to signify how it is wired.
Godspeed
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11-10-2016
Old 11-10-2016, 12:27 PM
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This is interesting. The pulse generator signal goes through a short coax lead (blue or green) at the distributor, then through a fuel injector style connector on the white shielded cable in the engine harness, then to the 8-pin connector on the CDI box. So, I guess what you are saying is that the outer sheathing of the shielded cable, which presumably goes to ground, is reversed in the green short lead, compared with the polarity of the original blue cable. Fixing it would mean removing the contacts inside the connector on the green cable, and reversing their polarity, right?

I cannot see why this would make a difference, but this is such a sensitive connection that I am ready to believe that it does. Can anyone explain why?

Last edited by Tom F2; 02-27-2017 at 01:59 AM..
Old 11-10-2016, 12:43 PM
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I don't understand how you can move the outer sheath section of wire from its position in the CDI box connector as that is the "common ground" on the CDI box. Maybe the common ground location is different on the early Turbo CDIs (as opposed to after 1977)?

Last edited by Rawknees'Turbo; 11-10-2016 at 07:25 PM..
Old 11-10-2016, 01:37 PM
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It seems to me that it is not necessary to reverse the connections. The output of the distributor reluctor is an ac signal. If the phase is wrong (due to changing cable) then the impact would just be a timing difference that could be easily corrected by readjusting the distributor position. Correct?
Old 11-10-2016, 08:12 PM
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I remember messing with that coax wire years ago.
If you reverse the polarity the motor still runs but timing changes quite a bit.
Old 11-10-2016, 08:20 PM
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It makes too much of a difference for good operation. The PO of my car had these mixed and timing was so advanced the adjustment range was not enough. IT rattled intermittendly at start up so I knew something was way wrong.

MSD instructions talk about this too.
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Old 11-10-2016, 08:46 PM
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Way out of my expertise, but had an expert spend a lot of time over the phone helping me troubleshoot a no spark issue that was a result of a failing CDI, a bent triggerpiont in my distributor, and a bad green wire. I'm only posting to share what I believe I learned, hopefully it will spark (yes I said spark )more discussion.

IIRC we looked at a graph of a CDI signal similar to the one bellow I googled (I believe this is from an SC, the 930 3.0 looked a bit different). He said the difference in the pins in the green wire had to do with what point of the signal was being taken, either the leading edge or the falling edge of the signal spike.

(Edited to eliminate incorrect deductions)
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Last edited by infraredcalvin; 11-11-2016 at 05:27 PM..
Old 11-10-2016, 09:07 PM
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Quote:
Originally Posted by infraredcalvin View Post
I'm only posting to share what I believe I learned, hopefully it will spark (yes I said spark )more discussion.
Nice! I tried to think of some way to parlay "spark" into flamer, or something like that, but gave up (guess I must be coming down with something - not like THAT )!

Although the thread is old, the subject is interesting to me because I've just recently had my hands on all the associated parts - replaced the distributor wire entirely (using the OEM shortie section from later model, non-turbo 911s and a length of appropriately sized, coaxial wire that I bought on Amazon), and had my CDI box out for re-build (a shameless glutes smooch for Bob Ashlock that posted above - excellent CDI craftsman with outstanding customer service).


Sooooo, the two pins on the distributor end of the wire are connected to 1) the inner, signal wire that is then connected to the outgoing signal pin on the CDI and 2) the outer, shielding wire that is connected to the common ground pin on the CDI. So, if you were to reverse the pins at the distributor, or switch them at the CDI (same result), the inner wire then becomes the ground and the outer becomes the signal wire. Is that what causes rough running (the absence of a shielded ground)? It must be, because reversing the wires would not do anything else other than what I just described (or I don't understand it at all). How would that have any effect on ignition timing?

So given that, if the early Turbo distributor, which turns in opposite rotation or the later ones, is hooked up as it it were a later one, then you would have the ground/signal wires reversal like I described about, correct? I can see how that would have a negative effect on how the engine runs, but do not see how that would do anything with regard to actual ignition timing . . .

Last edited by Rawknees'Turbo; 11-10-2016 at 10:31 PM..
Old 11-10-2016, 10:24 PM
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I think that Bob has nailed it - the timing is changed by 30 distributor degrees with the reversed polarity of the green lead, relative to the timing with the original blue lead. It is easy to correct for this by removing the distributor, shifting the gear by one tooth and then retiming the ignition. This, I suspect, is why the position of the distributor in my Turbo 3.0 is odd. The no. 1 TDC mark doesn't exactly align, and I can see where the timing nut and washer left a mark in a different spot previously. I recall struggling with the timing in 2002, when I changed the cable the first time. Since then, I have learned to carefully mark everything when I remove the distributor. Now I know why.

I think that the wave form is the same, whichever direction the reluctor rotates. All that the green cable does is to shift the phase of the reluctor wave by 180 degrees. (The reluctor wave goes 360 degrees for every 60 degrees of distributor rotation.)

I want to vouch for Bob's excellent work on CDI boxes, too. Really first class service and quality.

Last edited by Tom F2; 02-27-2017 at 01:59 AM..
Old 11-11-2016, 02:33 AM
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I too am interested in this as I piece back together a 77 turbo. As I understand it the shielded portion of the wire is not actually a ground and if you have continuity between it and the ground then you have a fault somewhere. Also the 30 degrees timing change caused by flipping these two voltage lines (which are voltage referenced) actually increases with RPM due to shape of the pulse which is inverted when the wires are flipped. The interesting thing to me is that on my 77 3.0 turbo which I'm piecing back together, the PO seemed to not even run a connection from the shield wire to the CDI and yet it ran at one time, years ago.
Old 11-11-2016, 03:45 AM
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Some important points made in the above posts:

(1) For the cable shield to do it's job of shielding the signal, it MUST remain grounded. This happens at the CDI unit where it connects at terminal 31/d (ground). So, if there is a 'reversal' of the phase of the signal due to a substituted 'green-wire' cable, the polarity/connection reversal should only occur at the distributor end of the cable. The reluctor coil itself is 'floating' (i.e., has no continuity to ground in the distributor), so it's OK to flip at that end.

(2) But, now I'm worried about my earlier statement about how flipping polarity will just make a small timing difference. Actually, it can make a pretty BIG timing difference (~30 degrees) which may not be solved by simply rotating the distributor. The distributor may need to be offset a gear tooth to achieve this.

(3) Finally, I just verified the waveform is assymetrical, as shown in the scope trace by 'infraredcalvin'. This means a polarity reversal can cause inconsistent accuracy of the timing/trigger event. The CDI is only triggered when the signal falls, not when it rises. (The trigger event actually happens when the signal falls to about +0.1V). As amplitude of the overall signal increases (with higher rpms), the fast falling edge is the only consistent trigger source (timing-wise) because the slope of the leading edge varies in time.

In the next post I attached a few photos showing the waveform before and after lead reversal. (I couldn't figure out how to add them by editing this post.)

My conclusion is that you cannot simply reverse the cable connection. Even after timing adjustments are made by rotating the distributor to compensate for the fundamental difference of reversing the polarity, the timing CONSISTENCY of the trigger pulse will not be as good.

Other comments/opinions are welcome. Expert Loren, guidance is appreciated!

Last edited by Bob Ashlock; 11-11-2016 at 09:17 AM.. Reason: clarifications and corrections
Old 11-11-2016, 06:53 AM
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