FLT6SPD

With the unfortunate failure in @Elliotw44 Wanted to get these pics out there so we can get a consensus of the different versions. @powdrhound

This was the latest revision when purchased and was told the hand etched number was the number of the modified version.
997-110-116-91 (1134)
Date code 06/02/2013
Purchased 2019ish from Fletcher Jones Porsche

This is still in the bubble wrap and has packing tape with a defunct company name of MWK Renningen Apparently this was the original OEM and QC obviously lacking.

Side to side play of the flaps are .032

Here are the pics:

FLT6SPD

More pics












The rest of the 4.0 lungs

powdrhound

Based on the above pics, it appears that the crux of the problem is the small Torx screws that secure the flapper to the rod are backing out and getting swallowed by the engine resulting in obvious engine damage. I am assuming these screws are simply secured via locktite in place? It seems a fix as simple as a small tack weld to the back of the crews would prevent this from happening.

I will take a look at the 3.6 (.90) manifold I have in my parts bin when I get back in town on Friday. My 2016 991Cup motor also has the .90 manifold instead of the .91. I find it interesting that Porsche chose to use the .90 version on the last version of the Mezger 3.8 991Cup motor instead of the .91 version.

Wonderdan

Ughh… I think I will bow out and install the Dundon plenum.

i see there is no way to easy way to scope, so we should prob add this to the cam bolt inspection when the engine is out?

Elliotw44

I learned my failed flap is the larger one.
'

Note that the latest part number is 997.110.116.95, which I ordered. Once I get that part, I will see if it has the updated part number or just the scratches and a P/N ending in 91. I am still waiting for an update from my shop on the current P/N on my failed Center Plenum.

Also, a picture of the cylinder inside with the failed piece. It doesn't look like a Torx screw.

FLT6SPD

@Elliotw44 It looks like the end of the shaft sheared off? The actuator side of the flap is still attached or is the whole thing dislodged?

How many miles, would like to correlate fatigue vs miles if any.

powdrhound

Wow. Looks like the end of the pivot shaft broke off which allowed it to dislodge. I did not expect that. That's bizarre as there should be very little force on the shaft itself, just the load of air flowing past it and pushing against it when the flapper is closed. I'm assuming some type of metal fatigue of the shaft from the vibration but sure points to a material defect of the shaft itself.

Elliotw44

The car had 40k miles on it when the failure occurred. This part was installed on 08/13, but I'm not sure of the mileage during install. When I purchased the car, it had 16k miles, so I'd wager this was about ~8-12k miles when installed.
Yes, it is interesting. Not what I expected.

CTS

The head studs are not stock. I don't know if this is relevant but it does complicate the diagnosis. Presumably the engine has other modifications too.

Chris

00 Scrub

Elliot, I'm sorry to hear about this failure. Would you be able to get pictures or microscope shots of the broken end of the TB shaft? It would be interesting to see if this was a fatigue failure over a long time or a sudden event and if this damage occurred in the closed or opened position.

Elliotw44

I am planning on doing a full teardown of the broken part. But that is going to be a while.

The 997.110.116.95 part arrived, and its part number on the casting actually ends in 91 with the written number 2603. The manufacturer is still MWK. Photos:




I noticed the shaft sits in what looks like a brass piece.

My failed part number is also ending in 91 but with the written number 1509
Looking at the failed piece in my engine, it appears that brass pieces were previously made of a different metal. That is a theory, but it is unconfirmed.

powdrhound

I was at the shop and spoke with Chris Cervelli about this issue as we will likely want to come up with a solution for my upcoming engine build later this year. The bronze bushings are a soft metal (compared to the rod) and act as a bearing for the rod. The whole idea of the resonance intake is the take advantage of the back and forth pulses created by the valves opening and closing and harnessing the energy to create a scavenging/supercharging effect on the intake air entering the runners. As a result, there is likely a lot of air "vibration" present in the intake manifold. This vibration is continually being transferred to the valves and in turn to the rod that secures the valves in the bronze bushings. There is a small amount of play in rod/bushing interface which may get worse as the bushing material wears over time. The continual vibration of the flap/rod assembly will eventually weaken the rod material and a fracture happens right at the rod / bushing juncture. All it takes is a tiny material defect in the rod or something as small as a ding or a scratch to act as a stress riser and that can accelerate the weakening of the rod material and lead to an eventual failure of the rod as seen in this instance. That is the theory anyway as I understand it and it makes sense to me. It would certainly help to examine under a microscope the broken rod that is attached to the valve dislodged in the intake manifold to make a more definitive conclusion.

RAudi Driver

So the dundon has none of these flaps? I don't see how this would make the car a better experience as I would want a car that feels lively at all RPM's not just the top end. Now I want to see what the inside of the 3.6 looks like.

ilko

Here are some pictures from my engine, taken a couple of years ago. The motor had 35K miles at the time of the failure...






Here is a photo of the part number of the manifold that failed, it was installed during the recall in 2013. Part number 997 110 116 91, dated 2013. The newest/current version of this center manifold is 997 110 116 95.


I posted my solution in the other thread, we installed screens on each end of that chamber, to catch any shrapnel, if the arm ever brakes again. Here it is one more time:


Finally... Andreas Preuninger and his team are well aware of this problem. He admits it in an interview with 000 from a few years ago:

bonehead

@Elliotw44 aw man. Just catching up with all this. Really sorry to see this.

All this time, the talk has been about failed screws getting sucked into the intake when it's actually been the shaft itself that's the weak point. Not that it makes a difference as far as someone blowing up their motor, but the solution unfortunately isn't as simple as tack welding as @powdrhound suggested.

So is it my understanding that those that have had these failures already had the updated part number installed?