Expanding ball micrometer. I also have a set of valve guide pilot tools, which I use to judge "overall" size/wear. I use them much like a "go/no go" gauge.

 

Yes, The big end on both the R1 and R2 rods are virtually identical. The R2 rod has changes where the beam meets the big end.

Tuomo mentioned something about the bolts coming loose on the R1 rods, which is why they got superceeded. I've never heard that. I though the problem was cracking where the beam meets the big end.

The Carrillos are much smoother.

I'm not sure how much effect that has on the oil. It sure would be fun to be able to see inside an engine and do measurements, while it was running.

 

The reluctance of the pins coming out is from the wrist pins battering on the circlips, which raises the aluminum on the outside of the circlip.

The GTS wrist pins and circlips do this much more than the other 928 engines. I always assumed that this was from detonation....however it could be from a lack of lubrication.

I was talking about this the other day, and someone said that they had never seen that happen. Here it is!

 

I am having chest pain just following this thread,,,,(and I am the erdoc on duty tonight, hahahaha)

 

The added material is in what I consider the big end and right next to the rod bolt saddle. Porsche calls it the "connecting rod bolt surface," but I think saddle is catchier. See below:



It would make sense that a failing rod might start pulling up, rotating, and binding the bolt in R1 rods. Specifically, the edge of the narrow saddle might bite into the bolt allow this failure mode.

Now that I am back from PR, I can see Rob's failed R1 rod bolts in fact sticking out a bit on the top in the debris (which proves nothing.) Here's a photo from an earlier thread:



I recall reading from some document that the problem was nuts backing up. I may have confused this with the criterion for rod replacement, which is a possibility. Human memory is a living thing.

I am also seeing Rob's piston pin photos for the first time with any clarity on my computer. I don't think one can draw any conclusions from those since they came from a failed engine. If you have metal in the oil, anything can wear/fail in many/any way, including the piston wrist pins. It would be more informative to see GTS piston pins which come from an engine that didn't fail catastrophically.

 

I pulled out a set of pistons I bought from Ali, '88 S4 with 94,000 miles. Randomly picked 4, and measured them vs. the 4 GTS wrist pins.

So overall, it looks like there's no measurable average difference between S4 and GTS pin diameters. But some of the GTS pins look like they've worn .0001 in the middle. The S4 pins don't vary across their length.



Also, here's the GTS pins on the left vs. the S4 pins on the right.

 

Greg mentioned he's got a box of GTS pistons at the shop, I'll grab them next time I'm up there and measure them to see whether there's any difference on pins from an engine that didn't go kablooie.

 

Interesting the GTs gudgeon pins are more 'stained' on their ends than the s4 pins. Is this indicative of anything, such as more oil down the Gts bores getting captured in the end of of gudgeon bore in the piston, or the gudgeon running hotter on the Gts and burning any oil residue, or both, or simply nothing?

 

I have seen this bulletin many years go- now that I have a GTS with a blown motor do you think I can write to Porsche and ask them for a new set of R2 rods? One could argue that the original motor from my GTS was stripped for maintenance [when it TBF'd].

I have a mind to pull a gudgeon pin from one of my pistons just to see if there are any signs of wear on the pin if anyone is interested.

By the way has anyone actually seen a R1 rod fail becuase of the perceived weakness Porsche chose to strengthen. that they did so just after the GTS was released suggggests to me they should have issued a general recall of all GTS motors but then of course they were all but bust at the time.

 

now were getting into the real technical part of the discussion and away from the banter:

"engine that went kablooie"........blowed up real good

"the gudgeon pin"........( Brit ) US and Canadian name: wrist pin the pin through the skirt of a piston in an internal-combustion engine, to which the little end of the connecting rod is attached

fantastic data and pics Rob....cheers

 

Yes, Porsche has a history of issues like this:

The new version:

http://www.autoweek.com/article/2014...NEWS/140319811

 

Which points back to Rennlist, 991 GT3 forum, and the Truly Epic "Stop Sale?" thread-- nearly 3000 posts long.

Wow! And we thought we had troubles...

 

Rob,

Is it possible your rod failed because of the inherent weakness in the R1 rod design? If so can you claim a new motor from Porsche or compensation because they failed to inform the PO/change out the rods? Given your system of litigation could that be leveraged if it could be proved that Porsche sold a "ticking time bomb"?

Looking at that rod photo of the residual mess it is not inconceivable that the rod let go at the shoulder that was reinforced. I have no explanation as to why the nuts ended up in the sump like that unless the force was so violent that they literally just "slipped off the bolts" during extreme shock but that would not seem to fit wilth a shoulder failure.

Regards

Fred

 

My #1 goal in life is to stay as far away from litigation as possible, so I won't be suing anyone, for anything, any time soon.

 

So the pins have a minute amount of wear. I'm very keen to see the wear to the small end bushing.