Hello, all.

I'm new to Rennlist as a registered member, however I've used the forum for learning purposes since February of this year.... that's when I bought my first Porsche. I'm a longtime Ferrari, Maserati, Aston and BMW (M) owner that finally decided to get a 911 within two weeks of learning that the '09s and up have no IMS.... a deterrent for me for some time (because of all the internet negativity and no real-world experiences)

Anyway, my 997.2 has the PDK, PSE and Sport Chrono Package (sport and sport plus). My issue is with the PSE. I understand how it works (the Ferraris also use Pierburg-type valved exhaust systems).... I understand that on this car the valves are normally open until vacuum is applied. The problem?? I can't hear a notable change in exhaust note whether the PSE electrical solenoid is connected or not. It seems to me that if I disconnect the solenoid valve electrical connector that the valves should lose vacuum and thus open..... even at idle, correct?

I have NOT tried getting a visual on the valves to see if their positions change during the connected vs disconnected state, but let's say the valves are open with the solenoid removed from the circuit..... if I still hear no change in sound, is it possible on these cars for BOTH side-mufflers to have failed?? Seems improbable.

Thanks in advance!

--nick

 

I have PSE on my car and only notice it at idle with the windows down, not from inside a closed cabin with quiet music playing. Where I notice a huge difference is above 3k rpms, it's much louder then.

Maybe take a video with your phone so you can hear the difference back to back? I bet you could even record the audio in such a way that you can listen to one side at a time. Just a guess, good luck!

 

You should certainly be able to tell some difference at idle (its pretty big if you have a center bypass, not sure if you don't), but especially so if you rev the engine.

Here are the possibilities as I see them (possibly in the order of testing?):

1. The signal to the switch isn't arriving. If you have a simple volt meter, you can unplug the connector on the switch at the top right side of the engine and with the test probes in each end of the connector see if it shows a roughly 12 volt reading that turns on and off with the in-cockpit switch.
2. If the current is switching, you don't know if the vacuum switch itself is working or if the switch is receiving vacuum. There is a T upstream of the switch that allows it and the resonator vacuum switch (at the right of the airbox) to share the same vacuum source. You could unplug the inlet at the switch to see if you get vacuum (you should be able to sense it with a wetted fingertip).
3. Next you could unplug the outlet from the switch to see if you have vacuum that turns on and off with the switch. If you passed the prior tests and fail this step, you know it is the vacuum switch. BTW, this is the same vacuum switch that you find to the right side of the airbox to control the resonator. You could try swapping switches if you wanted to just to verify operation. Just don't leave a vacuum line sit unplugged if you do a test swap since you don't want to suck anything into it.
4. You can do a similar vacuum test where the lines plug into the switch on the muffler but those can be hard to get to. There is also a very small clamp that keeps them secure on the switch that you'd need to loosen (although I think some cars use a spring clip but mine has a small philips screw head).

Since I ran my own vacuum lines when adding my PSE I know the routing of the lines and have a copy of the PDF at home showing their routing and connections. I can send it to you this evening if you think it would help. You could use it to help find and visually inspect all of the lines for disconnects or burn through... but again, they can be hard to see. You will certainly need to remove the airbox during this step.

 

I thank you both for your input. I'm an impatient man (when it comes to solving issues), so I immediately went home and performed a few of Storm's tests once posted. Here's what I learned.....

There's vacuum at the solenoid, yet at idle the valves are "already open". Here I am thinking my car should be louder when the PSE is activated, having had no baseline to compare to. Turns out it's always activated, which is disappointing considering how quiet it is.

During this troubleshooting I managed to find the valve actuator rods, so I pushed and released them while the car was running. This is how I learned they were already open. Now I know the simplest way would've been to see if there was exhaust flow at each of the outermost tail pipes When I push the actuator rods in, the exhaust flow from the outer tailpipe stops.

I could never get vacuum from the solenoid outlet with the PSE on or off, but I'm not sure if the DME keeps the solenoid from actuating when you're below a certain speed anyway. But, taking into consideration that I have full exhaust flow from all four pipes at idle, I'd say that either the solenoid has failed open, or somewhere between the solenoid and the valves there is a broken line.

I'll pull the airbox this weekend and trace vac lines. As for now, I'm OK with the valves being open at all times Just hope it's not a broken line.... meaning that small debris could be getting sucked into the solenoid and maybe into the intake?? I'd think a vac leak would cause a check engine.... no?

 

If the switch is never allowing vacuum through then the valves of the muffler will stay open/loud. The normal state of the valves on the muffler is open, the vacuum is used to close them.

If you are never getting vacuum from the solenoid in either state, then if I'm not mistaken your solenoid valve has failed and is stuck closed. Therefore the vacuum will never be able to make your exhaust silent. If you were getting no signal to the switch but the switch was good, the switch would stick in the open position. A lot of people simply unplug the switch to get the PSE to always stay on, so I think it is likely you are getting the signal just fine.

If it is the switch, that isn't hard to replace and retails for roughly $37 (although you can find it for less), assuming I got the part number right. The part number appears to be 99660512301 and an image search in Google appears to show the right thing. It also appears the part number is printed on the side of the switch, so you could take a look to make sure that is right.

You could possibly verify this is the correct solution by swapping with switch with the one next to your airbox, but that might be more trouble than its worth. Keep in mind that I could be wrong about this... I'm just calling out what I think it might be from a distant view.

 

You know.... rather than wait until the weekend to pull the airbox and trace the vac lines looking for breaks or burns, I could simply pull off the vac line at the solenoid outlet and connect my vac tester. Pumping it up should pull the valves closed. If it doesn't, I have a broken line.

Thanks for the help brainstorming! It helps to talk it out.

 

Sounds like a great plan. I didn't expect that you would have a vacuum tester!
Please let us know what you find out... and good luck!

 

Maybe the previous owner unplugged the PSE electrical connector in the engine compartment, which is a fairly common practice. That would keep PSE on at all times.

 

Dang! That's just so simple. It will be interesting to see if you are right... I'll give you good odds.

 

OK.... here's what I've learned using the vac test. Remember, this is my first Porsche, and I had no baseline "sound" for comparison. I just knew that at idle (and even when driving) I could tell no difference between PSE on and PSE off.

After disconnecting the solenoid outlet and connecting to my vac tester (no, the previous owner hadn't unplugged it. I had tried unplugging and plugging during troubleshooting, yet still thinking it wasn't working because there was no sound change), it turned out I had no leaks. The valves closed properly after pumping up the vacuum. They even held for a few minutes, so the valve diaphragms are good also.

So, after that, I tried Storm's suggestion again.... test to see if there is vacuum at the solenoid outlet. The first time I tried this, I had his advice backwards!!! I felt no vac at the solenoid outlet because I had the PSE "ON" (and I thought that was wrong). This time, I felt for vacuum with the PSE "OFF". Low and behold, vacuum was there. Turned the PSE on.... no vacuum from the outlet. At this point I'm thinking "ok, it's working now. So while I have vacuum at the solenoid outlet, let me reconnect the valve line to the outlet and the valves should close". The valves did NOT close, even though I knew there was vacuum at the solenoid outlet.

Conclusion......

My PSE system is working, but obviously the vacuum source is not strong enough to close the valves at idle. I bet that when I drive, the valves close with increased vacuum. My problem is that from inside the car I can't tell a bit of difference in sound with PSE on or off.... that's what started my whole suspicion!

I guess I'm making the mistake of comparing this valved exhaust note to the ones on my Ferraris. On these cars, the exhaust bypass valves even bypass the cats and exhaust directly into atmosphere.... no passing through any baffling when these bypasses actuate.

So.... everyone bear with me while I learn my "new to me" car

Now I have to learn how to drive it, as it has very, very strange handling/cornering characteristics from what i'm used to!!

 

Sorry that I wasn't able to help with any of the technical issues that you could be experiencing, but here is a video comparing PSE at idle from the cabin with the windows down.

Brake lights on = PSE off
Brake lights off = PSE on


Hope this helps!

 

Wow! This is NOT that obvious on my car at....all.......though now I know that the solenoid and valves are doing what they're supposed to do. Now you have me wondering why I don't have enough vacuum at idle to close the valves since obviously your car does

 

Mine is a 997, however, I'm backed up against a cement wall, so the sound reflection could have something to do with it.

 

Well, I know for a FACT that my valves are not closed at idle, yet the solenoid switch the flow of vacuum properly, the valves function well, and the lines from the valves to the solenoid have no breaks or leaks.

My car simply doesn't seem to produce enough vacuum at idle for the valves to close.

Perhaps now it's time for me to check the line that attaches to the solenoid inlet! Maybe I'm losing vacuum before the solenoid, which would actually be worse!

I'll test that tonight!

 

What were your vavuum readings?