kayjh

I was reading a C&D story yesterday on the 2017 911 base with manual. The car was equipped with PSE.

I'm confused with the operation of PSE. The article seems to say that even with PSE off, above 3,000 RPM the flaps open for a louder exhaust tone, but the test results show 83 db under full acceleration with PSE off and 88 with it on. Surely the full throttle test was above 3,000 RPM so with PSE off the flaps must be staying closed, even though the article says they open?

Can anyone with the option explain the operation? Can you force PSE to stay off with the button in the off position regardless of engine RPM or is C&D correct that regardless of the button position if you are above PSE you have a louder exhaust?

The article is here: http://www.caranddriver.com/reviews/...al-test-review

Dan Nagy

Yeah, I read that, too. That wasn't my understanding how it works, so hopefully somebody that has it will reply.

plenum

Don't have a .2, but assume PSE works under same method in .1 and .2 cars... The exhaust valves open either when engine hits a specific RPM or the driver hits the PSE button. Valves automatically close again when RPMs drop and PSE button is "off". The only thing the PSE button does is keep the valves open regardless of engine RPM, effectively giving the driver control. If you want valves open (either with or without PSE) all the time you have to stop the valves from working.

jimbo1111

I think your close ^ but I do recall a thread where Mr.Cable enlightened me a bit further as to how pse works in the .1. To my suprise he was 100% correct. That is, when PSE is engaged out of gear the PSE valves are fully open. The moment one accelerates in gear the valves close in order to help the engine build torque. Then reopen fully at about 3300 rpm to redline.
Now the .2 being FI I would thing has a different approach. Not sure how they function under load. I would imagine that the valves need to stay fully open to spool the turbos quicker. Might be best to cross post in the 991 big brother turbo forum for an answer.

kayjh

Thanks. If people aren't sure, I'll check with the dealer. Until I read the C&D article I thought the driver had total control over the PSE. I'm a bit sensitive to noise but everyone tells me I need the option for resale

RickIrons

There are basicly 3 levels, depending on the Sport settings:
1. PSE off: not really loud, quieter than PSE off on the .1 (to me)
2. PSE on, normal mode: louder and deeper sound, no "farting" when lifting foot from gas
3. PSE on, Sport or Sport+: Loud, screaming on high revs, farting when you lift off gas.
The exhaust sounds quiter to me when in the car than with the .1 model.

plenum

LOL I wouldn't put too much reliance upon your dealer, SA, or even the tech to get it right....

Best bet is to go through the official PAG technical papers on the feature, and even then I've seen people interpret what they read differently. For example, despite the various discussions on whether there is any performance gain, or torque loss, with PSE "on", the official PSE install WM states the following: "Engine power and exhaust behavior of the vehicle are not affected." There it is, right on page two of the "Installation and Modification Instructions" manual, document 27/12 ENU 2601 dated Oct 29, 2015. But, this doesn't address the deeper technical operations, and does not pertain to the .2 991's (yet).

I think I have more details documented somewhere... If I find it I'll post.

steve9

Is the standard exhaust on the .1 and .2 a valved system, even if not driver activated?

plenum

• Base .1 does not have valves unless you added the PSE;
• S .1 has valves with AND without PSE (difference is valve location, and center "x-pipe");
• .2 --- not sure....

You don't need the PSE option button to have a valved exhaust in other words....

Dirac

I can only speak to the 991.2 C4S without PSE. It IS a valved exhaust system. The valves open upon entering Sport or Sport+. There is a noticeable deepening of the exhaust note. I have no idea how this compares to the 991.2 C4S WITH PSE??

plenum

Consistent with the .1's all S cars have valved exhaust. Difference between that and PSE option was center muffler design and location of the valves. The center design of the PSE added a more aggressive tone. Base 3.4L cars without PSE were the only variant without valves. The .2 3.0L cars differ in turbo size between "base" and "S" versions but not sure if there is a diffference in exhaust shape. The Sport exhaust puts the tailpipes into the center....

Dirac

There must be differences. I ordered a FabSpeed x-pipe to replace my center muffler. It was meant to fit non-PSE exhausts. Wouldn't fit on the 4S. John @ FabSpeed was very gracious in helping me figure out the problem and (ultimately) returning it.

Jabs1542

Read the article carefully. I think what he is saying is that the Sound Symposer will not open the second port unless PSE is selected on, this is regardless of what the valves in the exhaust are doing.

PSE Off: exhaust valves closed until rpm exceeds 3K, and one Sound Symposer tube
PSE On: exhaust valves open, including above 3K, and two Sound Symposer tubes - thus the higher dB readings in the cabin

This was one of the differences between the 991.1 and the 991.2, the .2 has an additional Sound Symposer tube. Maybe that's what the .1 and .2 means, it indicates the number of Symposer tubes

BoldSharpe

Have you identified any other exhaust options for your 2017 4S? I also have a 2017 4S without PSE and want to give the car a more aggressive exhaust tone but think I can accomplish that with something a bit less expensive than retrofitting PSE.

Dirac

I'm hoping FabSpeed comes out with something, but I haven't talked to John about it. Maybe they just need a bit more interest....