Does anyone know the meaning behind letter designations in the Porsche parts catalog? I see it most frequently with washers. For example, look at items 6 and 10 below. Both are 8mm spring washers but with different letter designations and part numbers. Anyone know what the difference is?

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About $3.00 per washer vs. non-Porsche hardware.




I've often wondered the same. I'm looking forward to the right answer too!

You got that right! Okay Mr. Engineer, riddle me this one. In my example above, there are two attachments from the oil cooler bracket to the fan housing only about 3" apart. Both are attache with M8 x 20 bolts, both get a spring washer but different P/Ns for some mysterious reason, but only the upper gets a flat washer. Why? I have a guess but wondering if there is some secret engineering genius behind it I can't possibly understand.

Oh boy . . . this is going to set a bunch of folks on fire.



Here are my short answer guesses:

1) Different engineers releasing fasteners potentially at different points in time before they were collected up into a Bill of Material and the Service Illustrations & Parts Lists. Remember all this documentation was done in a pre-computer era. All hand work & lots of paper shuffling.

2) May be related to assembly line preferences of how easy it was to place a particular washer.

3) Different p/n could have been different plating finishes (black oxide vs. zinc), different tolerances (OD and/or ID hole size), or maybe different part suppliers.

My strongest bet is #3

Now here's the fun part to the pot.

Split ring lock washers ARE useless with respect to any ability to "lock" a fastener and prevent it from loosening. This is not some personal opinion said to be provocative. There has been an enormous amount of time and engineering spent since the birth of these cars to make fastener joints more robust.

Removal of lock washers from joints is a big part of increasing their robustness. You won't find split ring lock washers used on any modern automobile.

So my advice is don't sweat what type of lockwasher it is. Heck don't even use one. It won't amount to a hill of beans.

If you don't believe me that's fine, but, please first go read the NASA report. All the major automotive OEM's have done the studies and engineering as well. Fastener joints are more robust without a split ring lock washer in there.

https://ntrs.nasa.gov/archive/nasa/casi.ntr...19900009424.pdf

Pages 9 and 10 are relevant to this thread.

Here is the NASA except on split ring lock washers:

Lock washers
The typical helical spring washer shown in figure 14 is made
of slightly trapezoidal wire formed into a helix of one coil so
that the free height is approximately twice the thickness of the
washer cross section. They are usually made of hardened
carbon steel, but they are also available in aluminum, silicon,
brome, phosphor-bronze, stainless steel, and K-Monel.
The lockwasher serves as a spring while the bolt is being
tightened. However, the washer is normally flat by the time
the bolt is fully torqued. At this time it is equivalent to a solid
flat washer, and its locking ability is nonexistent. In summary,
a lockwasher of this type is useless for locking

Thanks for the short answer, can you expand on this a bit?



#3 is also my bet for why two different spring washers are speced. I did a little googling and it does look like one is bright zinc and the other yellow chromate. I'm not sure what difference it makes.

My question was unclear but actually more about why a flat washer on the top bracket and not the bottom. My guess is it is because of #2. The top bracket piece has a larger hole to allow some alignment flexibility both vertically and horizontally. The bottom bracket is ovaled to allow wider horizontal tolerance but not vertically. My guess is they though a flat washer was warranted on the larger hole to make sure the clamping force was transferred evenly.



This is interesting and something I've wondered about, but maybe not relevant here. One thing I've been able to decipher from the PET is that when they say "spring washer" they are referencing a wavy washer. A toothed washer is referenced as something like "shake-proof washer," and I believe the worthless old split lock washer is described as "lock ring" in the PET. At least that has held consistently true whenever I've compared the descriptions with known OEM parts. There are actually relatively few split ring lock washers specified in the PET, at least on smaller fasteners. As far as leaving split lock washers off... I'm the guy who replaced the "K" stamps on the trailing arms. Do you really think I'm going to do that? It would upset the whole aesthetic sensibility of these fine machines.

I knew that . . . . I just wanted to give you an out so you didn't have to fabricate your own from scratch

I've seen some nuts & mating surfaces with large gouges left from the split ring biting into the metal. IIRC, it's always been on larger diameter threads. Maybe it's best used on the larger threads e.g. 7/8" and larger. I've never liked using split rings on electrical. They're a bit too aggressive for brass and SS. PS, I like your build.

If you choose to go without lock washers substitute a flat washer or wave washer.
You won't have the locking feature but you will have spread the clamping force
over a larger surface and avoided surface gouging.

Check out the legend at the end of the PET for what those abbreviations mean

The V-Pages? That was the first place I looked but am not finding abbreviations for that column. I may be blind though.

I guess I'm curious if we are all referencing the same letter.

For example, on both #6 and #10 I see "N" at the start of the part number which would assume to be new addition per the legend.

However under the description, there is also an "A" or "B" followed by a number

per legend, would the "A" would be use until gone? However, I don't see a legend description for "B".

Item 9 for example lists "A 8,4" what is that referring to?

That's as far as I got too. Higher up on that key, they say they refer to "IN COLUMN -S- STATUS" There is no column S or status labeled but it appears to be the first column of the part number. I think I also saw a reference to an abridged version of the katalog somewhere which makes me wonder if some of the legend info was ommitted in this one

I did manage to figure out part of the A 8,4 by measuring several washers. 8,4 is 8.4mm. I forget now if that is ID or OD but they usually line up with standard (or at least available) washer sizes listed by Belmetric.

That's funny. I completely forgot about the Europeans using comma's instead of decimal.

At least that makes sense now!

'N' is a common prefix for non-specific parts like hardware. If you see a part number that starts with 'N' it's more than likely just a regular, everyday nut/bolt/washer.

As you discovered, the numbers reference critical dimensions. In the case of #9 above, the ID is 8.4mm.

I've never seen an official explaination for the A, B, AM, etc designations.

Usually the letters after the end of the part number are revision indicators. E.g., part "914.612.116 A" would be a later version of part "914.612.116", and so forth. I don't think they were always consistent with this nomenclature, though.

--DD