Just finished having my 87 S4's rear lined with dynomat/ballistic sound deadener. The guys at Go Audio here in Humble know the 928 and know just what is needed to limit the interior noise.
I can't believe much of a difference it make and how good the stock speakers sound with the right head unit. Can't wait to do the front half and wheel wells.

 

You will find the doors, B-pillars, front floor and footwells (mostly outside) make a big difference too...

Be warned if you do this that some sound deadening materials melt at high temp and leak out a nasty gooey residue (FatMat for one does this in very hot areas). This is most noticeable on vertical surfaces without very well sealed seams at the bottom cut edges. Sealing the seams with high quality foil duct sealing tape is probably a good idea. Hot areas include the tunnel area, tire well, outside door skins, roof etc...

Alan

 

I second Alan's advice. I had that happen on my 86.5 with Dynamat as well in Florida heat. The edges would leak very sticky butyl rubber and it would get on everything. Which is why on my GT project I am covering (secondary goal) the vibration dampers with a layer of Cascade Audio VB2.

Good luck with the sound insulation project. It is a big undertaking but I think you will be pleased with the result.

Cheers!
Carl

 

Thanks Alan and Carl, I will heed your advice. The cockpit road noise was a given in all the high performance sports cars and putting a damper on it just increases the already great driving experience we have being behind the wheel of our 928's. I am still amazed at the quality of the stock speakers, but then again, I am not an expert just love the combination, cruzin with good tunes.

Lon

 

Also forgot to mention that the pillars were done, just forgot to add the pic.

 

I have begun to do this project and have to undertake the rear wheel well trim pieces and pillars next. Doing the rear floor was a big change. I did leave my option code sticker uncovered as well as the access to the fuel tank.

 

Any before after db readings?

 

i used Fatmat.... ya, its gets goopy when on "hot" areas. being the car was in NM for a few years.... everything was a hot surface...... lol

 

Another factor is the road noise your current tires emit. Tire Rack is a good source for comparison ratings when it's time to replace. Also check out the last 3-4 pages of Carl's thread below, he is really doing a great job on his. T

https://rennlist.com/forums/928-foru...ed-car-13.html

 

Don't most owners go to lengths to try to reduce weight?

J/K...I would say though- given (my understanding of) how dynamat is supposed to function tucking it into the trim seems suspect to me.

 

It'll be fun replacing the fuel tank sending unit.

 

I was a bit surprised the fuel tank sender cover got done when I saw the pics - no way to drop the tank now.

 

I covered mine. It comes right off :-)

 

Porsche agreed on the need for noise reduction and greatly increased the foam padding under the carpet in 1990 then added inner rear wheel liners as well.

 

Now I know a new place to put sound deadener in my 81

Don't forget to put it under the foam that lies under the quarter panels, it helps with tire noise. Behind the speakers in the B-pillar is another good place, that area just amplifies tire noise.

Good luck on any future improvements