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I removed the symposer line between the vacuum activated valve and the plastic piece that transmits sound through the firewall.
I installed 1" drain plugs purchased on Amazon, https://www.amazon.com/dp/B0019LYCEE...ils&th=1&psc=1. I used zip ties to secure the plugs to the lines into which they are inserted so they wouldn't end up rattling around the engine bay if they were to come loose.
I also disconnected the vacuum line for the valve actuator, capping the metal line with a rubber cap purchased at a local auto parts store. The lines were secured using zip ties
Parts I used: 2 x 1" drain plugs (Amazon), rubber cap (purchased in a package of various sizes) and zip ties.
I tried rubber caps, but was not able to stretch them over the open tubes.
Once you have access to the engine, the job is simple. But it is challenging to work in such a small area that is not particularly easy to reach.
So I spent all afternoon figuring out mostly how the sound symposer works… this may be controversial, but I’m going to just report it like it is.
FYI, I have boxster gts with oem exhaust with a Soul VC installed as open/OEM mode. I’m leaning toward buying a Soul valved rear (only).
Anyway, I started by removing the rear carpeting. Then I got a partner and we drove around for a long time running a series of experiments in various modes.
1.) I used a spectrum analyzer on the phone to see if any of the settings made a measurable difference at idle. It’s pretty easy to stick the mic in the hole. Outcome: symposer does nothing at idle. You can sorta hear the valve activate (maybe) when you hit the sport exhaust button, but nothing at idle appears to alter the sound coming through that pipe in any way.
2.) The symposer has absolutely zero function when the sport exhaust is turned off. Zero. Tried everything. Symposer is silent. Sorry if anyone disagrees, but stick your ear up to it at any speed, any mode, any throttle position, any rpm. Nothing. I’m pretty sure the valve is just closed when sport exhaust is off.
3.) The symposer does function when sport exhaust is on. However, its output appears to be directly proportional to throttle input, at least after a certain point. It’s relatively silent at low throttle input, but if you floor it then the output appears to be generally proportional to the rpms. It is loudest above 5k or so under hard throttle. You can get it to be active in the 2k-3k “drone range” under full throttle, but its definitely not loud at all — and is most certainly unlikely to be causing any drone, unless you count drone as occurring above 5k.
4.) This may be a surprise to some, but it sounds good! Basically, it sounds like real induction noise (because it kinda is?). It’s easy to make it silent with your hand, so you can just simply sit there and control/modulate it with your hand. It’s amusing to control it with your hand actually.
5.) Sorry guys, but there is no reason to go to such great lengths to completely disconnect it. A plug of foam works as well as your hand, which just simply completely silences it. It’s not more complicated than that… I know someone used a tuning fork/audiology analogy early on, but that does not hold here; this is a flexible, low mass, little plastic pipe hooked to relatively well damped steel (there’s a raised ridge in the metal where the symposer comes in that will stiffen and kill most resonance in this area, and certainly any from a connected plastic flexible pipe).
Bottom line: it sounds good, and if you don’t like it, just push the sport exhaust button to completely disable it. No reason to pull the car apart. Lastly, and most controversially, this is definitely not the source of the high levels of resonance being reported (I can hear it too with valves forced open). For those who are hearing a difference after disconnecting, well, I think it’s not from this. But if you want to confirm, again, just use the sport exhaust button.
Also of interest, the rear carpet makes a huge difference in interior sound level. This car sounds like the engine is inside the cabin without that carpet and foam padding. You can hear the belts spinning and just more engine noise in general when it’s removed. The engine panel itself is not particularly well damped, so I added some CLD (dynamat) to the cover and to some of the other area that was not well damped before I reinstalled the carpet. The oem carpet has a plug of foam missing right where the symposer exits so that you can hear it better.
My conclusion is that the Porsche engineers knew what they were doing and did not introduce drone via their symposer. They delivered a good solution to a problem and added in some real induction noise under high loads at high rpms (and they probably enjoy reading these threads).
So it seems that my low-tech solution of plugging the hole behind the carpet with foam is actually the easiest way, after all, to accomplish the same as removing it all....imagine that.
So it seems that my low-tech solution of plugging the hole behind the carpet with foam is actually the easiest way, after all, to accomplish the same as removing it all....imagine that.
Yes, but the easier solution is to push the exhaust button. Pushing the button has the added advantage of being easily reversible.
My stance now is that unless a person feels very strongly about decoupling a very minor behavior difference in the exhaust valves from this intake valve behavior (recall the button actually affects both systems), then the best solution is to leave the symposer alone. You paid for that sound; Porsche built it; it sounds good; let it be! Who’s looking to remove legit intake noise at high/full throttle and high rpm?
Yes, but the easier solution is to push the exhaust button. Pushing the button has the added advantage of being easily reversible.
My stance now is that unless a person feels very strongly about decoupling a very minor behavior difference in the exhaust valves from this intake valve behavior (recall the button actually affects both systems), then the best solution is to leave the symposer alone. You paid for that sound; Porsche built it; it sounds good; let it be! Who’s looking to remove legit intake noise at high/full throttle and high rpm?
Sound is subjective so we all do what we like the best, and I like it plugged.
Excuse my ignorance here, but if the sound is piped into the cockpit via a hole in the firewall, couldn't you just plug that hole without have to go through all the machinations of accessing the engine and capping various tubes and intake ports?
Excuse my ignorance here, but if the sound is piped into the cockpit via a hole in the firewall, couldn't you just plug that hole without have to go through all the machinations of accessing the engine and capping various tubes and intake ports?
Excuse my ignorance here, but if the sound is piped into the cockpit via a hole in the firewall, couldn't you just plug that hole without have to go through all the machinations of accessing the engine and capping various tubes and intake ports?
Many of us did this while were in the engine compartment doing a Valve Controller install... Plus if done from the inside you still need to remove trim and pull back carpet.
So I spent all afternoon figuring out mostly how the sound symposer works… this may be controversial, but I’m going to just report it like it is.
FYI, I have boxster gts with oem exhaust with a Soul VC installed as open/OEM mode. I’m leaning toward buying a Soul valved rear (only).
Anyway, I started by removing the rear carpeting. Then I got a partner and we drove around for a long time running a series of experiments in various modes.
1.) I used a spectrum analyzer on the phone to see if any of the settings made a measurable difference at idle. It’s pretty easy to stick the mic in the hole. Outcome: symposer does nothing at idle. You can sorta hear the valve activate (maybe) when you hit the sport exhaust button, but nothing at idle appears to alter the sound coming through that pipe in any way.
2.) The symposer has absolutely zero function when the sport exhaust is turned off. Zero. Tried everything. Symposer is silent. Sorry if anyone disagrees, but stick your ear up to it at any speed, any mode, any throttle position, any rpm. Nothing. I’m pretty sure the valve is just closed when sport exhaust is off.
3.) The symposer does function when sport exhaust is on. However, its output appears to be directly proportional to throttle input, at least after a certain point. It’s relatively silent at low throttle input, but if you floor it then the output appears to be generally proportional to the rpms. It is loudest above 5k or so under hard throttle. You can get it to be active in the 2k-3k “drone range” under full throttle, but its definitely not loud at all — and is most certainly unlikely to be causing any drone, unless you count drone as occurring above 5k.
4.) This may be a surprise to some, but it sounds good! Basically, it sounds like real induction noise (because it kinda is?). It’s easy to make it silent with your hand, so you can just simply sit there and control/modulate it with your hand. It’s amusing to control it with your hand actually.
5.) Sorry guys, but there is no reason to go to such great lengths to completely disconnect it. A plug of foam works as well as your hand, which just simply completely silences it. It’s not more complicated than that… I know someone used a tuning fork/audiology analogy early on, but that does not hold here; this is a flexible, low mass, little plastic pipe hooked to relatively well damped steel (there’s a raised ridge in the metal where the symposer comes in that will stiffen and kill most resonance in this area, and certainly any from a connected plastic flexible pipe).
Bottom line: it sounds good, and if you don’t like it, just push the sport exhaust button to completely disable it. No reason to pull the car apart. Lastly, and most controversially, this is definitely not the source of the high levels of resonance being reported (I can hear it too with valves forced open). For those who are hearing a difference after disconnecting, well, I think it’s not from this. But if you want to confirm, again, just use the sport exhaust button.
Also of interest, the rear carpet makes a huge difference in interior sound level. This car sounds like the engine is inside the cabin without that carpet and foam padding. You can hear the belts spinning and just more engine noise in general when it’s removed. The engine panel itself is not particularly well damped, so I added some CLD (dynamat) to the cover and to some of the other area that was not well damped before I reinstalled the carpet. The oem carpet has a plug of foam missing right where the symposer exits so that you can hear it better.
My conclusion is that the Porsche engineers knew what they were doing and did not introduce drone via their symposer. They delivered a good solution to a problem and added in some real induction noise under high loads at high rpms (and they probably enjoy reading these threads).
Originally Posted by snrubel
Yes, but the easier solution is to push the exhaust button.
Pushing the button has the added advantage of being easily reversible.
My stance now is that unless a person feels very strongly about decoupling a very minor behavior difference in the exhaust valves from this intake valve behavior (recall the button actually affects both systems), then the best solution is to leave the symposer alone. You paid for that sound; Porsche built it; it sounds good; let it be! Who’s looking to remove legit intake noise at high/full throttle and high rpm?
snrubel;
I'm glad I found this Thread and most of all I'm glad I kept on reading to where I just saw and read both your Posts.
Sir you win as I will simply use the (Exhaust-Btn) and leave what Porsche built alone.
Ok. So I am one of those that was bothered by the drone between 2-3K rpms so I ordered the parts and just put them in. I will be honest I am not able to hear any difference. FWIW I have a FabSpeed valvetronic exhaust with their over axle pipes. I did notice they came out with a similar kit. I will continue to just keep my rpms over 3K lol.
@houstonbuckeye did you notice a difference in sound? (which car do you have again?)
I have a Spyder with straight OAP's and I really didn't notice any difference. I would have been surprised if I noticed a difference as the Spyder is quite loud with the uninsulated soft top, the particulate filters deleted and the valves open all the time.
Ok. So I am one of those that was bothered by the drone between 2-3K rpms so I ordered the parts and just put them in. I will be honest I am not able to hear any difference. FWIW I have a FabSpeed valvetronic exhaust with their over axle pipes. I did notice they came out with a similar kit. I will continue to just keep my rpms over 3K lol.
Oh well. I just wear earplugs on long distance driving.
This is why I opted to plug the hole coming into the cockpit...much easier with the same results, which are negligible.
When I was in the engine bay doing the exhaust valve install, I noticed that the symposer dead-ends into a wall of thick padding and carpet, which is behind seats. I wonder how much this thing can even do. Perhaps it's more about equalizing/adjusting pressure than actual sound. Isn't that what drone is caused by anyway, pressure? With modifications to exhaust, who knows what's best.
All I knew was that with 66 miles on my new car, I was in no position to make mod when so many others saw little improvements. In the next 60 miles I did noticed that the car is loud and maybe has drone, but I need more seat time before I can really weigh in on that. And with this weather lately, it's not looking like I'm going to get that any time soon, sadly.
But keep the feedback coming folks. Information is never bad.
11-01-2021, 12:30 AM
