Hi all, I managed to get a good result in tackling the excessive road noise on my 997.1, but had a few learning points to pass on if someone should google Porsche 997 sound proofing. You could make a difference to a 997 just by doing under the driver and passenger footwell and the outer rear arches through the speaker openings, which wouldn't take too long, but I went full monty and did as much as I could, adding about 5kg of soundproofing dynamat extreme. There wasn't much reduction in engine noise, if you have a sports exhaust you'll still hear it just fine.
Ultimately, I managed to get my cabin interior noise on the motorway down from approx 91db to about 87 using the decibel X app on my phone, which doesn't sound like a lot, but due to the exponential of how Db is measured, I've cut my interior cabin noise by half (noise doubles every 3 db) I still have new tyres to put on which will ultimately help a lot too. Ultimately, auwful sections of poor road will still transmit a lot of noise through any soundproofing, but I'm now much happier as it's now easier to hear the nicer aspects of the ehaust as it isn't all drowned out by tyre roar.
I ordered this pack of dynamat which was more than enough. If you want even better results than me, also consider some Dynaliner too. https://www.amazon.co.uk/Dynamat-10455-Xtreme-Bulk-Pack/dp/B00020CB2S
You will also benefit from a interior trim removal tool and a narrow rubber roller to press the film down.
This book is also very useful. 101 Projects for Your Porsche 911 996 and 997 1998-2008 (Motorbooks Workshop) https://www.amazon.co.uk/dp/0760344035/ref=cm_sw_r_cp_tai_PtXEAbG4HKKZT
I did the doors and driver passenger footwell first, followed by the rear arches. I decided that the doors were an important step as I measured the db in different locations within the car and it was also fairly high near the large speakers within the doorcards.
Doors-
Some of the clips in the door cards are very difficult and will almost certainly break off. It would be useful ordering five clips in advance. My end result was similar to what was achieved in this link, but Also made sure I left the side impact airbag eruption point in the door card clear of dynamat. http://www.audiofile-incar.co.uk/audio-upgrades/porsche-997
It is also important to remove the large speaker to give you access to the metallic skin of the door on the naked inside 'wet side' of the door, and you can apply a generous amount of dynamat where it will be most effective.
After the doors it is the drivers and passenger footwell, dynamating whatever I could underneath the carpet. The metal of the floor was very tinny here and my highest decibel measurement on the motorway was from the footwell and near the rear speakers on the rear arches. The footwells were relatively straight forward to do and didn't really need the front seats removing, I just peeled back the carpet and applied what I could. The only difficulty was unplugging the accelerator pedal which took about ten minutes of perseverance to press the pale coloured clip into the connector enough to release the plug. Once you've pressed the clip enough, it clicks and stays pressed into the connector. Some of the carpet is retained via contact adhesive so having some to hand for putting the carpet back is a good idea. Also be careful not to block your water drainage holes with dynamat.
Next came the removal of the rear trim and carpet. I left the drivers and passenger seat in to do this but it made the job very aukward. I would advise taking them out. Once the rear seats were removed and the trim was all peeled back I dynamatted whatever I could get to, paying particular attention to the rear arches. Contact adhesive again here was useful. Of note is that there is a significant amount of naked metal wheel arch just the other side of the rear speakers - if you move a bit of trim out the way you can dynamat a substantial amount of extra wheel arch through the rear speaker access hole. This is an important area which a lot of people will miss. I then used dynamat to cover over the hole in the chassis behind the speaker to seal it all off.
I eventually got all the trim back, the total job for the whole car took about 15 hours. After reconnecting the battery, both my windows wouldn't work, and failed slightly retracted, this was due to not quite connecting one of the purple electrical connnections in the drivers door. You also get a PSM failure caption illuminate on the dashboard after reconnecting the battery, which will clear fairly shortly after you start driving down the road.
If you are tight on time and don't have many tools / competence then you can definitely apply dynamat under the footwell carpet, and also onto a significant amount of the rear arches merely by removing the rear speakers.
Sorry for the massive amount of info but I hope it helps someone else if they are considering doing the job properly. I can still hear my exhaust just fine but now have a lot less road noise from the tyres.
Ultimately, I managed to get my cabin interior noise on the motorway down from approx 91db to about 87 using the decibel X app on my phone, which doesn't sound like a lot, but due to the exponential of how Db is measured, I've cut my interior cabin noise by half (noise doubles every 3 db) I still have new tyres to put on which will ultimately help a lot too. Ultimately, auwful sections of poor road will still transmit a lot of noise through any soundproofing, but I'm now much happier as it's now easier to hear the nicer aspects of the ehaust as it isn't all drowned out by tyre roar.
I ordered this pack of dynamat which was more than enough. If you want even better results than me, also consider some Dynaliner too. https://www.amazon.co.uk/Dynamat-10455-Xtreme-Bulk-Pack/dp/B00020CB2S
You will also benefit from a interior trim removal tool and a narrow rubber roller to press the film down.
This book is also very useful. 101 Projects for Your Porsche 911 996 and 997 1998-2008 (Motorbooks Workshop) https://www.amazon.co.uk/dp/0760344035/ref=cm_sw_r_cp_tai_PtXEAbG4HKKZT
I did the doors and driver passenger footwell first, followed by the rear arches. I decided that the doors were an important step as I measured the db in different locations within the car and it was also fairly high near the large speakers within the doorcards.
Doors-
Some of the clips in the door cards are very difficult and will almost certainly break off. It would be useful ordering five clips in advance. My end result was similar to what was achieved in this link, but Also made sure I left the side impact airbag eruption point in the door card clear of dynamat. http://www.audiofile-incar.co.uk/audio-upgrades/porsche-997
It is also important to remove the large speaker to give you access to the metallic skin of the door on the naked inside 'wet side' of the door, and you can apply a generous amount of dynamat where it will be most effective.
After the doors it is the drivers and passenger footwell, dynamating whatever I could underneath the carpet. The metal of the floor was very tinny here and my highest decibel measurement on the motorway was from the footwell and near the rear speakers on the rear arches. The footwells were relatively straight forward to do and didn't really need the front seats removing, I just peeled back the carpet and applied what I could. The only difficulty was unplugging the accelerator pedal which took about ten minutes of perseverance to press the pale coloured clip into the connector enough to release the plug. Once you've pressed the clip enough, it clicks and stays pressed into the connector. Some of the carpet is retained via contact adhesive so having some to hand for putting the carpet back is a good idea. Also be careful not to block your water drainage holes with dynamat.
Next came the removal of the rear trim and carpet. I left the drivers and passenger seat in to do this but it made the job very aukward. I would advise taking them out. Once the rear seats were removed and the trim was all peeled back I dynamatted whatever I could get to, paying particular attention to the rear arches. Contact adhesive again here was useful. Of note is that there is a significant amount of naked metal wheel arch just the other side of the rear speakers - if you move a bit of trim out the way you can dynamat a substantial amount of extra wheel arch through the rear speaker access hole. This is an important area which a lot of people will miss. I then used dynamat to cover over the hole in the chassis behind the speaker to seal it all off.
I eventually got all the trim back, the total job for the whole car took about 15 hours. After reconnecting the battery, both my windows wouldn't work, and failed slightly retracted, this was due to not quite connecting one of the purple electrical connnections in the drivers door. You also get a PSM failure caption illuminate on the dashboard after reconnecting the battery, which will clear fairly shortly after you start driving down the road.
If you are tight on time and don't have many tools / competence then you can definitely apply dynamat under the footwell carpet, and also onto a significant amount of the rear arches merely by removing the rear speakers.
Sorry for the massive amount of info but I hope it helps someone else if they are considering doing the job properly. I can still hear my exhaust just fine but now have a lot less road noise from the tyres.