zekgb

I have a bulk roll of B-Quiet Ultimate on its way and plan on doing the inner and outer skins of the doors along with the floor pans and hatch - wondering whether those of you who have done the outer door skins have removed the original asphalt deadener first as it seems to be on there pretty good and getting it out looks like a big job. Any harm in just laying the B-Quiet on over the existing stuff?

Alan

I think the original will be rock hard and brittle by now, some may break off easily if its loose - but so easy to damage the panel - I'd just leave most of it on.

Alan

martinss

There should be no problem adding on top of the existing material - I did.

There are different kinds of sound reducing products. Some, dampers, just add local mass to panels such as the door skin that change the resonant frequency of the panel so that it is does not vibrate in sympathy with external and internal noises. Dynamat and B-Quiet Ultimate are examples that also have some sound barrier capabilities.

In contrast, absorbers, which are typically single or composite foams or felts (in the past) absorb transmitted and reflected sound.

Composites combine dampers and absorbers.

If you consider the original materials in the 928, there are 'asphalt' pads on the door skins and sprayed materials on the floor pan to dampen vibrations, and there is decoupling foam with a hard 'plastic covering' to absorb transmitted sounds on the floor and transmission tunnel. This is old technology of course, and there are several areas where external sound transmission remains bad - the B-pillar and rear fender wells and even the floor being ones that Porsche obviously tackled somewhat over the years.

So in the case of the door, there is already a damper on the door skin. It is not necessary to cover the whole panel to achieve a dampening effect, which is why there is only a pad on part of the skin. Adding B-Quiet on top will add some barrier properties and others have reported benefits. An absorber would greatly reduce sound transmission but hurt the door speaker capabilities.

However, I don't think that the doors are the major sources of noises transmitted into the cabin of a 928 as others have reported. Doubling up on the doors, should be fine per your original question, but I think you will get a greater benefit addressing other areas.

The Forgotten On

Personally I left the factory deadener untouched as it would be a pain to remove and would damage some panels as mentioned above.

If you seal up the doors well with a vapor barrier and use the B quiet on top of the door to seal it even more, it will get rid of a lot of road noise that can occur from unsealed doors.

Covering the rear fenders with it also helps to reduce tire noise tremendously, it is also a good time to put some B Quiet inside of the B pillars behind the speakers.

For future reference only use butyl base sound deadeners as they don't stink like asphalt based ones do. They don't even have a scent when they inevitably get hot from sitting out in the sun.

Another place to add deadener to is the roof. There is already some insulation in there but it is old and should be replaced long with a layer of fresh deadener to help reduce road noise.

This is also a great time to replace all of the insulation with something newer that doesn't stink like the factory stuff can.

I used 3M Thinsulate in my 81 when I had the interior removed to redo the AC system. If it is good enough for Rolls Royce, it should be good enough for us

Petza914

Also, be careful on your choice of material being used on vertical surfaces, like the inside of the door. Some of these materials run when they get hot and could make a big tarry mess inside your door. I just did my Spyder while I have the complete interior removed for electric and leather upgrades. I used Eastwood's Thermocoustic product in the trunk, floors, fenders, etc but left the doors alone. It's both a heat barrier and sound deadened. I use Tyvek homewrap as my door panel moisture barrier. It's much tougher than plastic sheeting and works great.

Speedtoys

You can remove old deadener with dry ice.

On a vertical surface, put crushed dry ice on a towel folded over a few times to insulate it well, then tape it over what you wanna remove like a band aid.

Wait 5min, use a soft hammer to bump it off.

its even more dramatic on a large flat surface..pour it on, cover it, wait...wham..and it all flies off.

zekgb

I decided to leave the asphalt in the doors alone based on its condition and the difficulty of getting at it safely. Tonight I prepped the hatch and drivers side floor pans and there it was literally peeling up in multiple places so I spent a couple of hours with a plastic scraper prying the asphalt up, maybe 10 pounds of the stuff in total. Tomorrow I'll do the passenger side and everything will be ready for the B-Quiet which is due to arrive on Thursday.

martinss

you mention the front floor pans, but I also found adding B-Quiet to the rear floor pans, and then a layer of closed cell foam, made a surprisingly large improvement in reducing road noise.

zekgb

Do you mean behind the drivers's seat and in front of the rear seat? I do plan on doing those as well - the floors and rear hatch area will be done with a layer of B-Quiet topped with a layer of 1/4" CCF glued to 1/8" Mass Loaded Vinyl. Not sure if that same setup will fit in the doors, but may end up with just the MLV in the doors as a replacement for the moisture barrier.