I started a thread about this topic but am also posting in my Journal too in order to keep it complete. The thread can be found here: https://www.6speedonline.com/forums/...ues-991-a.html

I do not mean to light a fire for nothing, but I got increasingly concerned by what seems to be a lingering issue with change over valves in the 991.

Here's a picture of the part in question (the part number is 7PP906283B, now replaced by 7PP906283C):



Based on a quick research on the internet, it looks like Porsche was aware of the issue for early 2012 builds and that launched a recall campaign (WC-43) intended at replacing 8 of these valves.

In my case, my sport exhaust stopped functioning and 3 out of the 4 change over valves I have checked were bad (I did not check the others).

There are also various threads about 991's built at different times that have had heating/cooling system issued. Again, the same part was the culprit.

I find it intriguing that it has been going on for so long and that Porsche has apparently not resolved the issue.
The first concern I have is that you may not always detect that something is wrong: it is only when my sport exhaust stopped working properly that I discovered it, but the valves controlling the symposer and the intake flap were already bad. The second concern is that I read that this part would be used in more critical components (PDK).

Change over valves (simple solenoids in fact) are a very common part and Pierburg, the manufacturer, supplies it to a lot of car makers, including for the previous 911 models. This part number is specific to the 991 and seems to be the one having an issue. They may not be sealing properly allowing moisture in, causing the valves to malfunction over time.

I am not posting this to alarm you but to keep this in mind and report if you had other issues resulting from the failure of that same part.
Having already had 3 bad solenoids, I intend to drop the car at the dealership to get it checked.

 

Hey All,

I made a post in our thread about it, but since there is so much good info about the AWE Tuning SwitchPath Exhaust in here, I though it appropriate to bring the news to this thread as well.

The AWE Tuning Porsche 991 SwitchPath Exhaust is now available with some new additions, namely a new Diamond Black tip option, and a special hardware bundle specifically for Non-PSE cars.

The new Diamond Black tip option

Perfect for those looking to add subtle aggression to the rear of their 991, while maintaining a stealth appearance. The 90mm Slash Cut Diamond Black Tip option features the AWE Tuning logo, and double walling to ensure a mirror finish even under hard usage. The AWE Tuning Diamond Black Tip option is the perfect finishing touch for the perfect 991 exhaust.

In summary, the AWE Tuning Porsche 991 SwitchPath Exhaust is available with the following tip options:

• Chrome Silver 90mm Slash-Cut Tips
• Diamond Black 90mm Slash-Cut Tips
• No tips, for those looking to reuse their standard Porsche Tips

And now something for the Non-PSE crowd.

The AWE Tuning Porsche 991 SwitchPath™ Exhaust has officially been confirmed to work on cars without the Porsche Sport Exhaust option. The AWE Tuning SwitchPath Exhaust for non-PSE cars includes hardware specific required for installation on cars without PSE. PSE or not, we’re here for you.

Learn more, here, and please feel free to reach out directly with any questions that you have!

 

No worries, but PICS or it does not exist

 

Haha! I've got a set on my desk and will take pictures shortly.

 

Change Over Valves failure - part 2 I found the following schematic about the vacuum system in the 991 Service Information book (you can buy it from Suncoast BTW): It confirms my fear that more critical items can go wrong due to failed solenoids: I.e. shut off valves for engine coolant or ATF (= automatic transmission fluid for PDK). The Porsche document nevertheless mentions that "electric solenoid valves in the vacuum system are fully diagnosable (short circuit/open circuit); electrical faults result in an entry in the DME control unit and the PDK unit". I nevertheless did not get any alert for my failed solenoids and will definitely get the other ones checked ASAP.

 

WOW, that is scary. Very interesting that they use a mechanical vacuum pump, apparently the vacuum source from the intake isn't consistent enough. Seems like a lot that can go wrong since all of those things could be taken out by a single hose dying. I wonder what the airbox flap does. (the tuning flap is likely the intake manifold, and the others are self explanatory)

 

The airbox flap is no big deal in fact. There is a silencer (resonator) located in the air cleaner housing that is activated by a flap (controlled by one of our infamous solenoids). The resonator is closed for the most part and is open between 4,500 and 6,000 rpm.

The valve for the tuning flap (on the 991S only) is more interesting. The tuning flap is closed between 3,000 and 5,000 rpm and increases torque.
Everything is explained in detail in the attached schematic:



Despite the failure of the solenoids, the attention to details and technological refinement of OEM parts make me seriously question the relevance of some aftermarket mods, Take the plenum for instance, the Porsche part may be made of plastic, but is is equipped with a pressure sensor and tuning flap. Stuttgart engineers have spent hours making this optimum and I often struggle understand why a basic mechanic would be so much smarter by fitting something different.

The same applies to the airbox on the 991 IMHO:



if you look at how it is designed, it gets air where it is the coldest (outside of the car), the section is large and the filters are big, it is made of plastic which insulates better, has a low thermal mass and has a smooth finish and is shaped to minimize drag. Except for maybe installing high flow oiled filters (I did), I do not see how to perfect it.
But then, you have geniuses in a garage who put together 6 plates of metal, a big conical filter and a few bits of silicon hoses, name it a high performance cold air intake box and call it a day:



You can of course count on them to come up with dyno curves showing how much better they are that the complex Porsche design that was probably aimed at limiting the power of the car

I am not picking on aftermarket mods here. I like them a lot (and have done of lot of them too), but we should not underestimate the quality of the OEM design. There is a reason why P-cars are expensive and it is not only because of deviated stitching. Let's just exercise good judgement, keep a critical eye on things and discuss with vendors/tuners the true merit of their products first.

 

To be fair, most people do not like the goose caught in a trash compactor dying honk noise that an uncorked intake makes. There are certainly compromises made to make it quieter in some cars... But you're right, most modern cars are pretty well thought out in that area.

I also find it funny that the IPD plenums are so popular too... I mean, really you think Porsche would leave much on the table? (the X51 kit uses a different plenum but it's a similar design)

 

Ha ha, I'm one of those people and Serge has a point. To be honest I like the PSE, and I love the new GT3's sound too. I think the 991 is a more complete car. Yes, there are some mods that are good but I would sometimes leave the engineering to the engineers. For example, on 997's people were putting 20's and 21" wheels on the car but it was designed for 19". Which alters the ride and messes with suspension geometry. Duh, put 19's on the cars like the guys in the overalls told you owners! So like the OP says think before you mod.

 

Just got my 2014 Carrera and love to do the same for my rear reflectors. ANy tips on how to remove the rear reflectors? I'd hate to break something. Lol.

Thanks,
Joseph

 

I just installed IPD for 991, IPD do have the same flap as OEM. You simply need to remove both actuator and pressure sensor from the plastic OEM plenum and re-install into IPD plenum. It is pretty straight forward job, so IPD is design to work with the latest gadgets from Porsche.

One good thing about 991 is the infamous solenoid which controls the tuning flap is not located at the back of the plenum as it was in 997 so it is much easier to replace it on 991.

My Arkapovic exhaust did die on me due to the bad solenoid (change over valve) but this is an easy fix, I just need to replace it with the new one (revision C). However, I suspect that I might have a few bad one in my car so I did ask my mechanic to replace all solenoids since my car is 2012.

PS. PIWIS did not detect any bad solenoid on my Sport Exhaust.

Thank you for your great info!

 

Thanks for the info about the new IPD plenum. Pics on their website indeed show that the OEM gizmo's can indeed be simple transferred!.
There may be a thread about it already, but what are your impressions about the new plenum when you are behind the wheel?



No worries about the solenoids, they are very easy to replace and I wish Porsche was more proactive in fixing the issue...

Thanks!

 

Got the car checked by the dealership last week and all the other control valves were OK. I asked if they could be proactive and replace them preventively as 3 out of 8 had already failed, but as per PNA policy, they can only replace them if they have failed. Shortsighted approach IMHO.

I saw in a post on RL that Porsche has issued a TSB on this a few days ago. I'll try to get more info.

 

Back to the track!

I took the 991 back to the track for the first time since last September's accident.
I would lie if I'd say I wasn't a little apprehensive, but it was all forgotten after a couple of laps.

I am not sure it is a good or a bad thing, but my 3 year old is already turning into a petrolhead and felt like he had to prep his own car for the track too..



To make things worse, I went for Lightning McQueen-ish numbers on the car this time. Huge success with Petrolhead jr !



The track event was organized by Chin Motorsports at Road Atlanta. I may have said it before, but it is by far the best group I have seen so far (lots of seat time, fast and safe at the same time, extremely well coordinated).

There were also a number of interesting cars that were much bigger attention wh0res than a red 991:







...and a few novel concepts like this gas tanker truck:



I do not have pics of the track event yet, but I have ordered the usual photo set, so you will have to suffer it once again in a couple of weeks.

Meanwhile, here's a short video clip of the 991 following an Ariel Atom. The Atom should be faster than the 991, but I assume that the driver was a bit conservative that day. I'll be honest and say that I am not sure I'd be as confident in an Atom as I am in the Porsche, thinking about the consequences of an accident at high speed.


I also took the opportunity to record a longer sound/video clip of the AWE switch path exhaust. It sounded great and got me a lot of compliments from other drivers

Here's the GoPro ready to shoot:


and the video clip:

 

Awesome, Serge ! Thanks for sharing. Love the photos.

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