I had to replace the drivers door limiter because it wouldn't hold the door open. To replace it I would have to take the door card apart, so why not add deadening material? And why stop at the doors, why not make the C6 even quieter?
The C6 is quite different from the 406, it's already deadened to some level so my first idea was to add only small pieces of Dynamat for a 30% coverage to save weight and fill the door card with foam to stop sound propagation. Sound Deadener Showdown says a 25% coverage with a CLD tile is enough and you should use MLV to block sound and that's correct. If you apply a small amount of Dynamat or a similar butyl based tile the panel will stop vibrating, car manufacturers do this to save weight.
But why settle for less? Sure, the difference in noise reduction might not be that big, but if I'm going to deaden the car why not aim for the best possible results? I'm not going after 100% coverage, but probably 80% or near that. Let's see if I can make the C6 whisper quiet like a Rolls-Royce and block heat to make the inside cooler in the summer.
When deadening a car the doors are the place were the biggest difference will be felt. They are right on the drivers side and allow noise to enter the cabin. Also the doors will feel solid when closing, like a luxury car. But on the C6 the doors are already deadened, so will I feel any difference?
I took the door card out and unlike the 406 there isn't much space to work around. As you can see the door sealing sheet has a white piece of fabric to decouple it from the door card.
After pulling the door sealing sheet out, carefully not to damage it, I saw that I had little access to the door, but it could be done with patience. There was already some tiles applied with a butyl base, but the back seems to be plastic, not aluminium. If it's aluminium it's very thin.
After cleaning the outer door skin I applied Dynamat Extreme. This is a new bulk pack, so it is now black instead of silver like before. It's more discreet, but In my mind I always associate the black colour with a hot car.
At the middle of the door there is some sort of fabric deadening that is quite cool to the touch. Since I want to keep the car cool I didn't apply anything on top. To avoid rattles in the future the window support mechanism received some bits of Dynamat just to add mass and stop vibrations. Since the door will stop vibrating, other parts might vibrate when listening to music, for example.
At the middle of the door there is an impact absorber with some kind of foam at the back, so it's decoupled from the outer door skin. Still I added a few bits of Dynamat to avoid vibrations.
With most of the outer door skin deadened I added some smaller pieces of Dynamat to the inner door skin. Unlike the 406, were I covered the entire outer door skin, on the C6 I would hit the metal to see if it vibrated. I would then apply Dynamat to add mass and stop the vibrations. When it sounded solid I wouldn't add any more Dynamat to save weight.
After this I applied Dynaliner 1/4" on the outer door skin to block heat and some extra noise, covering the Dynamat Extreme that was applied.
I didn't add Dynaliner to the impact absorber because then there would be no room for the window. I know it doesn't look that pretty, but I would waste a lot of material to make cuts that would precisely fit. With the door sealing sheet in place no Dynamat is visible.
After this I closed the doors to test if when listening to I Remember by Deadmau5 the door would still vibrate. I know, I should be hearing Enya or Cinematic Orchestra. I do, but I really like Deadmau5. Back on topic, the vibration was still there, it was the window lifter motoreducer. I tightened the bolts but was still a faint vibration. I was sure this would be inaudible with the door card on, but I added some Dynamat on top of it and the vibration was gone. Unfortunately I didn't take any pictures.
On the door cards I applied some Dynamat Extreme to add mass. This will avoid vibrations and rattles when listening to music. I didn't had any Dynaliner because the door card is already decoupled, even the clips that hold the door card have some sort of foam were they meet with the metal. Saves me some extra work.
I also added some foam around the tweeter that stays near the mirror. Since it's all plastic this will avoid rattles.
Final notes and results
It took me 1 day per door, about 1,5 sheets of Dynamat Extreme per door and almost half of a sheet of Dynaliner per door, totaling approximately 1.5kg per door. Since Dynaliner comes in a single sheet, one box was enough for two doors and there was still a bit left.
Here's a top tip if you have a C6 and want to deaden your car. When doing the passenger door I removed the window lifter motoreducer and that gave me some extra access. This way it wasn't necessary to remove the front speakers, which are riveted to the door.
The door feels more solid when closing and it's a nice feeling opening a heavy door. Now, like on the 406 I can't hear the cars passing by, only when they are behind and the noise enters thru the rear doors.
Regarding the noise measurements, at idle there was no difference at all. At speed I got 63dB at 120km/h, almost a 2 dB reduction.
The biggest difference was in the sound system, now I have more bass and there's less noise from the music outside the car.
Done in 03 of August, 2014