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PET says 79-85 are all the same, 928 612 007 01. I have one here from a '79, I get 11 feet 3.5 inches center to center, not quite pulled taught, so 11'4" is good.
As shared previously in this thread, I ended up buying a little extra, then did the final trim-to-fit in place before finishing the starter-end lug installation. I figured that it was easy enough to trim a little (very little it turned out) so all the cables fit together in a nice bundle where they loop from the crossmember back across to connect at the starter solenoid. Certainly easier than trying to stretch the cable a few inches.
Reading back through some of this thread to refresh memory before posting, I note a mention of using a 3/8" holed lug for the starter end. The lug on the solenoid for the battery and other primary connections is 8mm, which works out to a 5/16" hole rather than 3/8" (closer to 10mm). If you are shopping for lugs and have the option to get one with 8mm hole, it -might- make a cleaner installation.
Purists: 8mm is actually 5/16 + 0.003". The holes in the copper lugs are not quite that precise, usually generous, so they are effectively the same diameter in this service.
Just got my 1/0 starter cable in and thought I'd share some measurements for those who look to do this in the future:
1. Diameter of the cable is ~14.25mm:
2. Opening for the cable holder (new) is ~12mm:
3. I opened up the holder a bit with a drill bit, and after some shaving was able to get it to fit. I think the cable deformed a wee bit to become more oval, but seems to work:
And since I was getting a new starter cable, I figured I'd get a new engine ground as well. Went with a 4/0, which I'm sure is waaay overkill, but as the saying goes - bigger is better (or so I'm told). ~18.5 mm of fine wired grounding cable
At least on later cars with full belly pans, I suspect exhaust heat will damage the insulation on covered ground straps. Plus the cover will hide any corrosion whe water ends up inside the cover. Just be aware.
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The motor mounts I received from Tom at 928 International arrived with plated steel ground straps that bridge around the motor mount. I didn't install them or even see how they might fit with the mount installed. Eyeball engineering says they will.
Resurrecting this old thread because I'm replacing the engine harness on my '83 US, and while I'm fiddling with the starter terminals I may as well toss in a new/upgraded/better starter cable to replace the original. Porsche still does have the original cables. Even though I strive to maintain originality virtually everywhere, at approximately $250 for the original part I can build my own, including the crimping tool, for far less -- and make it BETTER! (Would it be sacrilegious for me to use RED wire by the way?)
I've decided, based on the discussion in this thread, that 1 AWG is probably the best gauge. And whatever I get should be rated to 105 C. (This has been a very informative and helpful thread!)
And I have some heavy duty FTZ copper terminals on the way, 5/16" ring. And also ordered a massive crimper tool that will go down to 1/0 gauge.
So some questions:
- I haven't seen mention of OFC cable. Thoughts on going with an OFC cable such as this one? https://ceautoelectricsupply.com/pro...nt-red-jacket/
The above cable is OFC, 1 gauge, multi-stranded and tinned, rated 105C.
Alternatively, there was a mention of SGX cable earlier in the thread -- what's supposed to be so great about that? My quick check seems to show that SGX refers to the insulation, not the wire, but not sure why that was said to be the best?
- Second, what are folks using for the battery positive terminal connector, is anything special required there?
- Finally for my '83 should I re-use the existing hold downs or get new ones, what do most folks do? I have to admit I haven't inspected mine yet...
OFC is an interesting up-charge but is also pretty meaningless in a tinned-strand cable like this. The tinned marine cables tend to be very fine-strand, a Good Thing as there are some interesting bends in the cable as it follows the tub and bends around the suspension mount and such. You'll be very glad it's a little more flexible than standard battery cable in the larger size.
There's nothing special about the battery post end except that you'll want the cable insulation to be vapor-tight where it meets the terminal itself. I ended up soldering that terminal to the cable before putting it in the car, and using a good high-grade adhesive-lined shrink sleeve (2 layers) to make sure no corrosive vapors would get back into the cable.
Red is probably OK for your car. I went back with original color black. The Ancor cable I used has a gloss to it that the original didn't. I don't suspect the judges would notice that, but for sure they would see red.
SGX cable does in fact refer to the insulation, same as other cable type designations do. SGX IIRC is suitable for use in mining equipment and similar service where abrasion resistance and resistance to cutting is of paramount importance. It's way overkill in the 928 application, where the cable is very well supported, and is pretty well protected by sitting up snug next to the rib in the tub, clamped or shielded around that rear suspension pickup point, and otherwise tucked up as it passes the starter on the crossmember in front. SGX insulation is also pretty thick, almost forcing you to use metal P clamps instead of the factory pieces.
I re-used all the factory hold-downs, pretty easy since the Ancor marine cable I used worked out to about the same OD as the original.
I might add that I used a piece of Home Depot sprinkler connector hose for the sleeve where the cable turns and routes past the power steering gear towards the starter. It is cheap, looks like the perfect original part, and is readily available. For lss than $2 on a whim, it was probably the cheapest part of the whole project.
Last but not least, I have to admit that the new cable did absolutely nothing to help the voltage drop problem I was chasing. It looks real pretty, kept me busy for an afternoon, chewed a corner off my 928 project credit card, but no other benefits were apparent. It was the battery ground strap replacement that actually improved my charging and voltage drop symptoms. Original still looked "OK" but no better. 2ga tinned-strands replacement strap went in after some shrink tubing was applied, then the wiring to a rear battery maintainer plug was bundled inside a second layer of shrink tubing with the ground strap. That way it's all very well protected where it passes out of the battery well and past the spare wheel on the way to the rear apron.
I'll be back in there in the next few days. The battery has a couple weak cells (specific gravity test) discovered as part of the annual electrical maintenance protocol. I decided to try the "recondition" function on my fancy CTEK battery maintainer, and need to go back in to retest the specific gravity of the fluid in the cells again to see it it actually helps. Else, it's times for a new battery. Related: The battery in the car is over five and probably pushing six years old. This is about the longest that any Porsche-fitted battery has lasted in all the years and all the cars. It's a WalMart MAXX, and has done a pretty stellar job all its life with me. The local store doesn't keep the Group 48/ H6 size in stock, so I'll end up with an Interstate from the local Costco at a little under $100.
Last but not least, I have to admit that the new cable did absolutely nothing to help the voltage drop problem I was chasing.
I just "discovered" this thread and was so excited about replacing my cable, and then you posted this! lol I guess you just saved me some money and time. thanks....I guess.....
Thank you Dr. Bob, you always have so much useful and actionable information. Thanks for the details on the battery connections, both of them, which I will replicate (I actually just received the new factory ground strap but the braid is slightly exposed so I'll shrink wrap it. Oh, and I'll also route the battery vent as you explained earlier).
I like your comment about chewing off a corner of the credit card, I feel like mine has been consumed entirely once or twice over lol!!!!
I'm not chasing any gremlins, merely doing this for peace of mind and, well, because... it's kind of fun. Twisted, I know.
looking forward to hearing about your results. perhaps you could take some before and after volt and resistance measurements?
I was chasing some lingering charging symptoms when I did the replacement, and had gone so far as to string some test leads to the ends of each section of cable to try and find where I was losing. Each section tested fine, the car cranked well until it didn't thanks to the battery not getting fully charged. I looked hard at that main battery cable before leaping into the project, since it looked and tested fine. The R&R took a little longer than I had originally estimated. Not too hard, just a little time consuming as the cable gets carefully fitted. Eventually, I followed the group recommendation for a new battery ground strap even though mine looked great (on the outside...) and tested fine in service. Charging issues instantly solved, for a less than $20 all-in upgrade investment.
I'm not advising that folks don't replace their cable based solely on my experience. Other people with other cars may easily have other symptoms and other results. Just sharing that for my situation with my car, my alternator and my battery, the pretty new cable I assembled and installed didn't solve my problem.
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A reminder: I was chasing some of the same symptoms that drive others to look at upgraded alternators. Living above Los Angeles (literally...) meant that daytime driving was often slow and go in traffic, warm days in a black car with AC and fans running. With the battery not accepting a full charge from the alternator, the dash voltage reading would dip down to 12 while sitting and soaking. This problem had crept up gradually, and was not at all apparent when the car was almost-new in my early stewardship years. I even stooped to replacing the original alternator, thinking that might be a normal wear/deterioration item even though the test instrumentation showed it to be fine. One more cleaned and refurb'd spare part into the 928 parts bin... Adding a higher-voltage alternator masks a lot of the symptoms I was chasing. But to take advantage of that extra low-RPM charging capability, you'll want to upgrade the original wiring with new higher-current capable conductors anyway, and that was the thought process I was following. Anyway, replacing the primary cable was part of an iterative effort that I generally avoid when possible.
After posting the last couple to this thread, I decided to go back and re-read all the posts starting at the beginning. The evolution of the project from the beginning is pretty well documented, but more important there are a lot of posts that share information or stimulate more discussion. It's a very worthwhile read for all that's included.
01-23-2017, 01:51 AM
