Diablo Dude

Still subject to speculation.
The aluminum casting process could have been contaminated.
Could have occurred during a specific time period, which could explain why some cars have suffered a failure, while others (that arent even tracked) have.

BillC3

Not really.

First, my comment was in response to Porsche's claim that the failures are not a manufacturing defect. If it's not a manufacturing defect, and it's not caused by abuse, then the remaining option is a design defect.

Second, all the failures -- on both sides -- happen around the top of the towers, just under the reinforcements cast into the underside of the top of the towers. The design of the strut towers and strut mounts make that area a real stress concentration, and Porsche apparently just didn't reinforce it enough to handle all of the loads.

Third, there are also recorded failures on GT3s and on 718s. If there was a batch of bad castings, the failures should have been constrained to a certain range of production dates, like the 3rd gear failures. However, there has been a fairly wide range of vehicles suffering the failures, so probably not a bad batch unless the batch is huge or there is a recurring production issue that should have been identified by now.

Fourth, the problem seems to be linked to lowered front suspensions and/or very large bumps. Porsche designed the front suspension without any rubber bump stops. So, when the front suspension is completely compressed, the spring rate effectively goes infinite and shock loads are delivered directly to the towers without any mitigation by rubber stops. Aluminum is notorious for failing under repetitive shock loads, even those that don't reach maximum allowable loads.

cmosman

GoKart, what is the part number of this plate you are showing above? There seems to have been a revision, as the earlier plates did not bolt to the windshield wiper assembly. That "ear" was cut off.

r
Earlier revision:

f50nut

Noticed this myself regarding the updated version on the driver side when I installed the plates from SP last weekend.

I’m no engineer but I can’t see how the wiper mounted section does anything on a street car given the hardware used to secure the wiper assembly. There’s a rubber bushed spacer in between the bolt and the wiper arm, so there’s no way to tighten that bolt enough to transfer load away from the tower IMO. Seems it would make more sense to run the earlier version sans wiper mount on a street car. The wiper assembly and anything it bolts to could be another series of parts that will break in the event of failure.

This is not the case on the passenger side, as the mounting point inside the cabin filter housing is metal to metal.

GoKart Mozart

I think it is the same p/n. They must have cut those ears off for some reason. Maybe because they were made for Motorstport, Porsche weren't worried about attaching it to the windshield wiper assembly on those cars, but figured (at first) that when mounting them to street cars they should not squeeze it under that assmebly? But clearly it fits.

My 02 cents on these plates. While it looks like they strengthen the shock towers, I think there is some room for improvement (which is where my idea comes in to play). Based on the pictures I've seen of several failed towers, it looks to me like the first place they let go is towards the front/center, and these plates mostly strengthen the rear area, because that is where they are bolted in to two additional places. While I'm sure it prevents some of that load and transfers some of the pressure, I would feel better if they were attached to another area in the front/center, which I believe is possible.

I haven't taken it apart myself, so I can't say for sure, but I highly doubt it's secured with a rubber spacer in between. It might just be a rubber ring around a steel spacers to help dampen vibration from the windshield wiper assembly. Keep in mind this is where the strut, that connects the shock tower and firewall, mounts to. I don't think they would have held that down with rubber spacer in between.

f50nut

I’d love to be wrong on this. While tightening that bolt you can watch the rubber compress and squeeze out from below the washer. I just set it to the same torque spec as the 3 strut tower nuts (24 ft/lbs).

GoKart Mozart

If that is the case then you are probably correct. Like I said, I never took it apart, so I was speculating.

cmosman

Well, for sure it's not the same p/n, because it's not the same part
Can anyone confirm the part number?

On the subject of strut-tower reinforcement using these plates - IMO they do nothing in terms of strengthening. What they do is (1) prevent the car falling to the ground in the event and (2) retain some level of controlability, even if the actual shock tower top is completely broken off. Without the plates, the hood will hold up the car, but there is very little control when the strut top is completely loose.
So - no need to force the plates down as hard as you can. They are just "emergency straps".

trkshoe

Why the heck dont we have bump stops... that would go a long way in mitigating the impact taken by the tower... this will be my next 'to do' on the car.

hellboy_mcqueen

I was thinking the same thing.
I am not an engineer but i really dont see how such a plate can help to strengthen the tower to the impact from below.
It must be just safety in case tower comes off.

cmosman

These plates are motorsport parts, i.e. they were conceived for race cars, which use carbon hoods, and the 718 CS the hemp weave/balsa wood compound. Neither are strong enough to hold up the car, will break, and leave the driver stranded. Whereas with the plates, they can get back to the pit at a reasonable pace. Needless to say, the race is over, regardless. So, think of it as a safety device in terms of car-controlability. Will be at an event by a team that runs a 718CS, maybe I can glean the p/n.

GoKart Mozart

I thought the same thing for the longest time, but the more I look at it, the more I actually do think they help. My theory is that the front/center of the strut towers still would want to crack and could, but these plates should transfer some of the load towards the back and that is a good thing. They kind of act like a hinged lid on a pot for lack of better terminology. So while it would be better if the "lid" was secured on the side it wants to lift up, it still should be better to have one on it, even if it is clamped in the back. Also, keep in mind these plates are stamped with bends in them, which makes them very strong. The key really is that they bold in to a couple of places outside of the top. If it was just the top 3 strut bolts, then I would agree 100% that they are useless.

All that being said, I would like to find a way to anchor them on the front side, and I have some ideas on how to do that.

domkrz

You’ve got my support. Now that Porsche has taken care of the transmission issues all we need to do is figure out the strut towers and we’ve got a pretty robust car on our hands.

GoKart Mozart

Thanks. The challenge is that I can't really do any testing like Porsche could. All I can do is make something that I think will help prevent the failure, and time will then tell. I am in contact with a Porsche aftermarket parts supplier. Actually I recently machined some parts for him. So the two of us will put our heads together next week to see if my idea could work. He should have the distribution network and "store front" so that would certainly help move things right along.

4carl

This is what i said about a year ago. Some one said that there was an internal bump stop? I have my doubts as Ive yet to see one. I think because of the lowered ride height they figured there wasn't enough stroke length to accommodate a stop? carl