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Not contradictory at all. The ultimate goal is to have the right sounds at the right places!
This sound pipe an example of when "over-engineering" for no good reason happens. Good thing there is a relatively simple solution for it.
Im going to go out on a limb here and assume Porsche knows exactly what they are doing with every bolt, gasket, **** and button in their cars. Therefore these 'weird' decisions are just that much more suspect related to their motivations in selling their cars. This being my first Pcar maybe Im just not 'indoctrinated' enough and these decisions stand out like sore thumbs. Maybe its just the Porsche way.... "Hey cayman buyers, we are going to make a super GT4 718 and just to make you think its superer we will pump in some sound because we have to kill the exhaust note because of the EU regs." and my favorite.... "Hey we can't let the 718 GT4 handle THAT much better than the 992 out of the box so we will put in a fixed rear toe link to limit the alignment and screw with the perfect chassis that way." Ugh... infuriating! But these 'annoyances' have their fixes thanks to the aftermarket and RL!
OMG. Well I can hardly believe it! This mod really works to cut down the resonance/boom/drone and overall interior negative sounds. I have the Cargraphic Valve Controller, Kline Inconel OAP and rear on my GT4 w/PDK. I did not think the car was much louder with the Kline vs the OEM exhaust, but the car is 'loud' inside no matter what - my issue with stock was the quality of the sound along the rev range and especially above 6,000 rpm. So much so that I would drive with the windows down to not have so much interior noise and, on occasion, I would take to putting in ear plugs! Now with the entire sound symposer pulled out and the fire wall hole plugged with 80 mm Dynamat the interior is much quieter over all. The drone ranges still exist but as others have said, the 'noise' is cut in half (about like having the ear plugs in!). I have to drive a bit more to see if at higher revs the car still satisfies. I think though overall its an improvement in livability, especially since wife's (and to a lesser extent mine) major complaint was the drone/loud interior. Ill update in a bit after a longer test run. I used a regular 1" drain plug and the methods of removal described above. Big thanks to John @Soul Performance and everyone else who commented on this mod - I think well worth it if your are sensitive to the interior sounds of this car.
PS. One other note... I did use some of the extra Dynamat to cover the both the engine cover and the firewall behind the seats since I was there anyway. I did this to maximize my returns on taking the car apart again (3rd time!). I dont know how much this helped with noise cancellation but probably some....
PSS. Yes I recognize the contradictions here perhaps to some extent of going to an after market exhaust and then quieting the interior... but its really about sound quality and when the sound is heard along the rev range. I think if John and his crew are exploring this with their mission being towards performance, then I think its safe to say we are in good company!
Not this time. If you scroll up in this thread, all the necessary pics, instructions and parts I used are described above. I just followed those before me. The only different thing is I used 6 - 16"x10" (approx) 80 MM thick dynamat sheets - three on TOP (metal side) of the engine cover and three behind the seats under the carpet/sound proof. Just peel off the sticker and slapped on, easy. Good Luck!
Not contradictory at all. The ultimate goal is to have the right sounds at the right places!
This sound pipe an example of when "over-engineering" for no good reason happens. Good thing there is a relatively simple solution for it.
The right sound at the right places is exactly why Porsche chose to have the exhaust valve close in that specific middle range. They knew the drone was annoying. I'm running stock exhaust with a valve controller, and when it's set to always open, the drone is quite annoying to me in that high 2k to 3k range.
Are there basic instructions for removing these lines? How long did it take?
Assuming you're in the engine bay already, unplugging the vacuum line takes 10 seconds or less. Just wiggle it off (don't use enough force to break anything)
Well, I am in there now and the hose that goes from the cabin firewall to the vacuum port has a 1" internal diameter but the ends that go to the vacuum valve and the connector attached to the firewall are larger... I measure the openings at 31mm or 1-1/4"
If you remove the tube at the vacuum valve you could use a 25.4mm (1") plug there and in the tube end but this means you have to leave the tube in place and connected to the firewall fitting.
I was hoping to plug those openings and remove the symposer entirely... Hmmmm
Well, I am in there now and the hose that goes from the cabin firewall to the vacuum port has a 1" internal diameter but the ends that go to the vacuum valve and the connector attached to the firewall are larger... I measure the openings at 31mm or 1-1/4"
If you remove the tube at the vacuum valve you could use a 25.4mm (1") plug there and in the tube end but this means you have to leave the tube in place and connected to the firewall fitting.
I was hoping to plug those openings and remove the symposer entirely... Hmmmm
Just rip it out of the firewall side. Then I used 80mm Dynamat. 2 pieces on the inside and 2 pieces in the cabin side. Worked great. Use the 1" float screw plug thingy to screw into the tube just before the vaccum valve which I removed. Remove the entire symposer and the bracket and 'bobs your uncle'!
Just rip it out of the firewall side. Then I used 80mm Dynamat. 2 pieces on the inside and 2 pieces in the cabin side. Worked great. Use the 1" float screw plug thingy to screw into the tube just before the vaccum valve which I removed. Remove the entire symposer and the bracket and 'bobs your uncle'!
Yep a little zig then a zag and I should have it... no Dynamat on hand so... I am thinking to remove the vacuum valve assembly, plug the vacuum line and use a 1" plug there, remove the symposer tube entirely and plug the opening to the firewall with a 1-1/4" plug..
Yep a little zig then a zag and I should have it... no Dynamat on hand so... I am thinking to remove the vacuum valve assembly, plug the vacuum line and use a 1" plug there, remove the symposer tube entirely and plug the opening to the firewall with a 1-1/4" plug..
Cool, that should work. Let us know what you think when all back together! My wife doesnt complain as much about the noise level in the cabin... so thats something. Im even now thinking the Kline 200 cell Inconel headers wont be too loud inside....!!!
Cool, that should work. Let us know what you think when all back together! My wife doesnt complain as much about the noise level in the cabin... so thats something. Im even now thinking the Kline 200 cell Inconel headers wont be too loud inside....!!!
Hey did you know there are some other 200cell Street Headers from yours truly that you could consider as well?!
Cool, that should work. Let us know what you think when all back together! My wife doesnt complain as much about the noise level in the cabin... so thats something. Im even now thinking the Kline 200 cell Inconel headers wont be too loud inside....!!!
Well, although not what I would call dramatic the reduction in drone is noticeable... I removed the entire symposer tube and vacuum valve assemblies, plugging both the firewall opening and the chamber at the intake with 1" expansion plugs, my config is with Akra OAP's and JCR silenced Rear sections.
What I note is that any sound that was coming from the symposer is of course now gone, but sound coming into the cabin through chassis resonance remains. I feel that the effort and cost make it a worthwhile exercise but don't expect it to eliminate drone, at least in my opinion if your exhaust configuration drones then it will continue to do so but the symposer will not amplify its effect in the cabin. During top-up drives the cabin drone was better and you could easily tell it was reduced, but lug the engine in a high gear between 2000-2600 RPM and it will drone. What was easier to determine was the frequency change between valves open (higher) and valves closed (lower), but I would say the volume was similar in either setting.
Comparatively a buddy with a GT4 and completely OEM exhaust system felt it was a game changer, what was before tiring and unbearable while cruising was nearly cured by this mod, he said he could have a normal conversation in the car where as before it was not possible.
So at this point your results may vary depending on GT4 versus Spyder (top up/down) and if you exhaust is stock or modified.
Well, although not what I would call dramatic the reduction in drone is noticeable... I removed the entire symposer tube and vacuum valve assemblies, plugging both the firewall opening and the chamber at the intake with 1" expansion plugs, my config is with Akra OAP's and JCR silenced Rear sections.
What I note is that any sound that was coming from the symposer is of course now gone, but sound coming into the cabin through chassis resonance remains. I feel that the effort and cost make it a worthwhile exercise but don't expect it to eliminate drone, at least in my opinion if your exhaust configuration drones then it will continue to do so but the symposer will not amplify its effect in the cabin. During top-up drives the cabin drone was better and you could easily tell it was reduced, but lug the engine in a high gear between 2000-2600 RPM and it will drone. What was easier to determine was the frequency change between valves open (higher) and valves closed (lower), but I would say the volume was similar in either setting.
Comparatively a buddy with a GT4 and completely OEM exhaust system felt it was a game changer, what was before tiring and unbearable while cruising was nearly cured by this mod, he said he could have a normal conversation in the car where as before it was not possible.
So at this point your results may vary depending on GT4 versus Spyder (top up/down) and if you exhaust is stock or modified.
Good summary thank you, and having an OEM example along with the modified example makes for a useful bit of data.
That's what I wanted to hear. I have a stock system and have assembled the necessary parts, plug, dynamat and caps for the vacuum hose, just need to jump on it now. Thanks for all the work on this mod. I just wonder why Porsche did this in the first place, adding unneeded sound in an already noisy cabin.
Last edited by Bill Mitchell; 07-20-2021 at 07:28 AM.
That's what I wanted to hear. I have a stock system and have assembled the necessary parts, plug, dynamat and caps for the vacuum hose, just need to jump on it now. Thanks for all the work on this mod. I just wonder why Porsche did this in the first place, adding unneeded sound in an already noisy cabin.
Bill, FWIW, I gave the tube into cabin through the firewall a twist and pull but didn't see an obvious way to release it and since everything I do on my cars needs to 100% reversible I didn't try to hard for fear of breaking it, so... Although Dynamat will certainly cover the opening once the fitting was removed, the 1" expansion plug can be installed in less than a minute and provides a firm seal and is completely reversible in about the same amount of time.
07-11-2021, 12:17 AM
