Is there any way to bypass the factory trigger points for opening up the exhaust valves? I have PSE, and have replaced the center muffler with a Cargraphic X. I'm wondering if there's a way to force the valves to remain closed when the flaps are in the closed position (they open with moderate throttle input above 3300rpm).

Thanks!

 

Forgive me if I misunderstand your question.... But I think the short answer is no. Regardless of PSE or non-PSE configuration the valves are opened either at specific RPM or by the operator pushing the PSE console switch. There is not a switch to close the valves when opened. And "shutting off PSE" while you are driving doesn't automatically shut the valves either until you're RPM fall to the trigger point. The only options for shutting the valves permanently would be to either delete the valves altogether with the non-S base 3.4 exhaust (as I don't believe the valves are there at all on the 3.4) or an aftermarket exhaust.

Can I ask why you would want to do this? I don't think the valves remaining open above 4k RPM is just for sound -- maybe keeping them shut might cause performance issues at wider throttle speeds???

I'm no expert tho! So maybe I can learn something here.....

 

Oops! I think I recall seeing somewhere that Cargraphics offers a separate valve on-off switch. Maybe that is what you want?

 

Hey jawells,

Thanks for the info. I understand the way PSE valves work, and how shutting off PSE won't automatically silence the car unless you're simultaneously reducing throttle input.

I guess my point is to reach exactly that point, though: to be able to force the valves to stay closed in any circumstance, throttle position, RPM, etc. I'd just like to keep the car quiet during morning commutes and casual driving, even if I go over 3,300rpm in a single gear.

I do remember Cargraphic and other exhaust manufacturers offering their own controllers. But, would these be standalone devices that basically override PSE's controls? Or would I, or a shop, be able to somehow incorporate that controller into Porsche's own system so that the PSE button can be used to perform the same function?

 

The 2014 Cayenne GTS has an override switch so that when you put it into Sport mode (which also automatically turns on PSE) you can still hit the switch to kill the PSE sound (but still have Sport for throttle response, gearing and suspension setup). So maybe a hack is possible for the 991S.

 

The valves are open/closed by engine vacuum pressure which is actually controlled by the car's DME unit (computer), which is turn does it based on RPM. It's all an electronic activation. Here's what it looks like:



So, a constant vacuum source will either keep them CLOSED or OPEN all the time, and I'm not sure on the 991 as I haven't investigated it. Easy way to tell is crawl under the car and pull off the vacuum lines on the valves, then go for a ride. They will either be all the way open or all the way closed. If closed, then cap off the lines, put a cap over the valve input and you're in business. If they stay OPEN, then that's not helping you but perhaps you can put a call into the dealer to see if they can override the function on their master Porsche settings computer and leave them closed all the time. I would think they should have that capability, its just a software fix.

 

Thanks, TT. We also have an override button (the actual PSE button, if that's what you're talking about). When Sport Mode is activated and the exhaust valves are opened, you can click the PSE button and manually close the valves.

The problem, though, is that the valves automatically re-open about 3,300rpm with moderate throttle input.

Awesome. Thanks for the info. I'll give this a shot over the weekend.

 

Im pretty sure it takes vacuum to close the valves. Keeping them under vacuum could be a matter of manipulatimg the signal, that the ecu sends to the Change Over Valve, with an additional switch.

CO valve has just 2 wires, so it is basically a relay.
An auxilary SPDT switch can hold it closed or open.
Basically selecting ECU Control or Overide Mode.
You could do it with a detachable harness so no wires would need to be cut.