mgerber

I finally had a chance to see and hear a couple of GT4s today at the Exotics At Redmond Town Center gathering. In addition to being impressed with how the cars looked I was stunned at how good they sounded on startup and when accelerating. From outside the car the exhaust certainly sounds loud enough, and IMO is one of the best sounding factory exhausts (as others have indicated). Both owners were thrilled with their cars and were happy to answer my litany of questions. One line of questioning I had was around the louder exhaust setting and whether or not it had the usual cutoff around 30mph for drive by noise regulations. Unsurprisingly both owners indicated that the exhaust seemed to quiet down in that speed range. My question for you guys that already have your cars:

1. Is the shutdown of the louder exhaust note in the 30mph range very pronounced? For the PSE systems I had in my 997s the shutdown was very noticeable – I needed it to go away and did the bypass mods.

2. Have you done or are you planning to do a bypass mod (to leave the valves open)? I did this a couple of different ways on the 997s (aka cutting and blocking the vacuum hoses to the exhaust control valves) until I realized the easiest way to get it done was to unplug the electrical connector in the engine compartment that controls the vacuum to the valves. My guess is that the connector for this is still on the manifold which is buried in the GT4’s engine bay. I know this makes the console button useless, the system is on the loud setting continuously, there is risk that some track noise regs will require the quiet setting and there is risk in the valves becoming inoperable if they are not used for a long period of time. All the more reason for looking for the easy and reversible way to do it with the electrical connector.

Although my neighbors don’t, I like a louder exhaust (and have a Fabspeed Supercup on the 993). It’s one of those inner child impulses I just have not been able to suppress after all of these years

BTW - the GT4 will not be my DD so the extra noise will not be an issue.

jphughan

Is it that important to have a loud exhaust below 30 mph, or is it just a jarring transition that's irritating?

RussellNYC

I don't notice any quieting down at 30mph. This sucker seems as loud at 15 mph as it is at 30 mph. Tons of crackling overrun at parking lot speeds.

Tass

I didn't notice it to be any quieter below 30mph, it did get much louder now that I have over 4000km's on the car though :-)

mgerber

IIRC (and it has been a while) the DME shuts the valves at approximately 30mph and then opens them again at approximately 40mph. This was done to pass some of the drive by noise regs in Europe which I believe have changed. The transition in the 997 was very pronounced and for me it was irritating. So for me the issue is not having a loud exhaust below 30mph, but having the exhaust both quiet down abruptly and in the middle of rolling on the throttle in that speed range. I was hoping this is not the case with the GT4, but without the car...

mm1

Can't say I notice it quieter with PSE on. When it's on, you'll know it. Off and it's pretty mild and just as quiet as my S4 coming into the neighborhood at low revs BUT at higher revs it's still pretty loud even with PSE off, louder than my last 997 C2S with Fabspeed crosspipe for sure.

user1029

Of course it is important to have a loud exhaust 100% of the time. You have to show those Prius's who is boss when they are deep staging you at the stoplight

KingSize.Hamster

I've asked this question in another forum before. It appears that some owners don't find that there is a need to bypass the speed/rev sensor. Personally I found the 987/997 generation PSE and even the 991 GT3 rather whimppy at lower speeds. But then some would argue it's loud enough, while others would argue that a noticeable loss in lower end power would come into play. Others then argue whoever does this mod is silly as Porsche engineers have spent a lot of effort and testing on to this system.

Anyway, personally I did the bypass mod on my old 987.1 CSS' PSE and loved it. It's hard to explain what you are trying to do for those who have never tried doing this on another PSE previously actually.

mgerber

Agreed that it is hard to explain if you have never done the mod or experienced the earlier generation PSE cutting out at those speeds. It was hugely annoying to roll on the throttle in that speed range and have the engine sound contradict what you felt. IIRC the "pull the brown plug" mod became really popular in either 2008 or 2009 after an interview with Andreas Preuninger when he indicated that the need to quiet the exhaust in that speed range was due to drive by noise regs which require dB measurements within that speed range, and discreetly suggested to find the brown connector and simply unplug it. That interview quieted down all the hoopla about power loss, warranty concerns, etc. - even our dealership techs were doing the mod when customers asked. Without my car to play with I figured I would ask folks that have theirs to see if the latest gen PSE has that "feature". I suspect from the comments so far (or lack thereof) that maybe the need to quiet the exhaust in the 30-40mph range is no longer a requirement (?).

Ochocoronas

IMO once PSE is on its fully on the whole time. We need someone to mount a Go Pro under the car and see if the vales move when PSE is on. I did find this out by real time testing. I was in 2nd gear at 45 MPH pushed in the clutch and gave some throttle blips with sports and PSE on it is much quitter than PSE only.

KingSize.Hamster

The best way to do is just to pull the vacuums line out.

I too felt that there was no concept of "active" exhaust system before, but once I did the hack on my old car? You can never un-hear it. I'll do that in a few months if no one else tries it before then.

Basically, that's the order of loudness at lower speeds / revs on my old car (and supposedly the 991 GT3s as well):


PSE @ Quiet is level 1 loudness
PSE @ Loud without hack is level 3 loudness
PSE @ Loud with hack is level 5-6 loudness

Whatever the 1 to 6 scale means. It's just a relative thing. Anyway, there is just one way to find out the results ...