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C6 sound insulation

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Radox   
Mon May 25 2020, 04:50pm
Joined: Aug 27 2019
Member No: #4044
Location: Bad Bergzabern
Hello, I tried posting this thread a few minutes ago, but It didn't show up, so I guess I will have to type everything again...

My C6 is a little bit too loud for my linking (both at high and at low speeds). However, from what I've heard from other C6 owners, their cars are pretty silent and comfy, so can the problem be in my car?

I downloaded a sound measuring app and at 100 kmh, with aircon and music turned off, it shows 78 dB. I think this is a little bit too much. However, I haven't driven other C6s, so I can't compare it.

So, I have the following questions:

1. Can part of the problem be in the two big insulation panels (behind the engine and above it, on the underside of the bonnet). After all, mine are almost 14 years old and could have deteriorated. Can these be changed and do you think it will improve anything?

2. At speeds above 100 kmh, I hear a pretty loud windy noise from the driver's door. Is this normal, or the door must be readjusted, so it fits better? I have also noticed a small hole in the rubber band that runs along the door, where the glass rests upon closing it. Is this a factory hole, or is my seal damaged?

3. Have you noticed slight vibrations in both pedals when the engine is on? Can these be eliminated or it is normal?

4. Can the car be additionally insulated by adding new layers of sound absorbing mats in the doors, under the floor carpeting etc.?


I'd be very appreciative of any feedback and help, because I travel a lot in my C6 and want more silence.
C6Dave   
Mon May 25 2020, 05:22pm

Joined: Oct 01 2009
Member No: #1
Location: Northumberland
1. Possibly

2. Take a look at: - Click Here -

3. Not noticed personally but the engine mounts have a 'damper' in them so maybe need replacing?

4. Additional sound mats will always help (I put a lot in the Traction Avant but more would still be beneficial!)
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3 User said Thank You to C6Dave for this Post :
 Radox (25 May 2020) , cruiserphil (26 May 2020) , gkirkov (31 May 2020)
Radox   
Mon May 25 2020, 08:22pm
Joined: Aug 27 2019
Member No: #4044
Location: Bad Bergzabern
C6Dave wrote ...

1. Possibly

2. Take a look at: - Click Here -

3. Not noticed personally but the engine mounts have a 'damper' in them so maybe need replacing?

4. Additional sound mats will always help (I put a lot in the Traction Avant but more would still be beneficial!)


For point 2 - I think the sound is coming exactly from the area that you are saying! Will see if I can seal it over the weekend.

As I see you are pretty proficient with C6s, I have another question for you if it's not a problem. Is the following behavior of my suspension normal. I have found a topic about this from 6-7 years ago, but it doesn't contain a conclusive answer:

1. After driving, when I turn the ignition off, the car sinks immediately by 1-2 inches (I think this is normal)

2. Then, the suspension slowly rises about 1-2 inches over a few hours

3. When I UNLOCK the car in, say, 6-7 hours, the suspension sinks immediately, only to slowly rise to its normal heigh when I turn the ignition on a few moments later.

4. However, if the car stays locked for more than about 12 hours, then the suspension is again sunk and upon UNLOCKING, the pump turns on and rises the car back again.

5. The suspension LDS pump always makes a pretty audible whirring noise when working. I think this is also normal?

Thanks in advance.
Tjensen   
Mon May 25 2020, 08:28pm
Joined: Jul 17 2012
Member No: #954
Location: Bergen
Everything is normal and programmed this way. It will sink to make it easy to come out/in. Otherwise, it will go to "normal". But it might have been sinking when parked for a long time, so then the normal down will be up. And more complicated fun when driving.
C6Dave   
Tue May 26 2020, 07:47am

Joined: Oct 01 2009
Member No: #1
Location: Northumberland
Radox wrote ...


For point 2 - I think the sound is coming exactly from the area that you are saying! Will see if I can seal it over the weekend.


If that doesn't work then you may need to 'adjust' the glass fitment.

There is a Technical Document on the front door glass fit and adjustment - Click Here - though hopefully you don't need to do that.
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1 User said Thank You to C6Dave for this Post :
 gkirkov (31 May 2020)
Fraunie   
Tue May 26 2020, 09:53am
Joined: Dec 09 2018
Member No: #3763
Location: Stockdorf
I downloaded a sound measuring app and at 100 kmh, with aircon and music turned off, it shows 78 dB. I think this is a little bit too much. However, I haven't driven other C6s, so I can't compare it.


Where exactly have you positioned your phone? Where to is the micro pointing at?

I am happy to try it myself, we could compare the level then...
Radox   
Tue May 26 2020, 04:02pm
Joined: Aug 27 2019
Member No: #4044
Location: Bad Bergzabern
Fraunie wrote ...

I downloaded a sound measuring app and at 100 kmh, with aircon and music turned off, it shows 78 dB. I think this is a little bit too much. However, I haven't driven other C6s, so I can't compare it.


Where exactly have you positioned your phone? Where to is the micro pointing at?

I am happy to try it myself, we could compare the level then...


The app is called Sound Meter in Android store. I drive with 100 kmh and the phone is on the central armrest between the two front seats. Its mic is pointing towards the rear seats.
1 User said Thank You to Radox for this Post :
 gkirkov (31 May 2020)
Norman   
Tue May 26 2020, 10:23pm
Joined: Feb 06 2011
Member No: #364
Location: Huddersfield and Torremolinos Spain
For point 2 - I think the sound is coming exactly from the area that you are saying! Will see if I can seal it over the weekend.

As I see you are pretty proficient with C6s, I have another question for you if it's not a problem. Is the following behavior of my suspension normal. I have found a topic about this from 6-7 years ago, but it doesn't contain a conclusive answer:

1. After driving, when I turn the ignition off, the car sinks immediately by 1-2 inches (I think this is normal)

2. Then, the suspension slowly rises about 1-2 inches over a few hours

3. When I UNLOCK the car in, say, 6-7 hours, the suspension sinks immediately, only to slowly rise to its normal heigh when I turn the ignition on a few moments later.

4. However, if the car stays locked for more than about 12 hours, then the suspension is again sunk and upon UNLOCKING, the pump turns on and rises the car back again.

5. The suspension LDS pump always makes a pretty audible whirring noise when working. I think this is also normal?

Thanks in advance.




I Find none of that happens on my car when i get into the car and turn on the ignition the pump starts but the car is at normal ride height from the previous journey and when i stop at the end and turn the ignition off it stays at normal ride height i thought that this is what it was supposed to do!

Regards Norman
Jas16   
Fri May 29 2020, 01:56pm
Joined: Feb 07 2017
Member No: #2994
Location: West London
My car also sinks when ignition is turned off and rises when I unlock the car. Always assumed this was normal. Especially when we all sit in the car and add load.

I will be interested in the A pillar noise, if you do go ahead with this, I seems to hear more noise when it is particularly windy and almost like the window/door is open.

Edit: I had been quoted approx £800 for a days work to have the interior of the car inc door panels [i] modified with additional sound insulation. For me this was a bit much at this stage. I can forward details if you like.
1 User said Thank You to Jas16 for this Post :
 gkirkov (31 May 2020)
Fraunie   
Fri May 29 2020, 02:02pm
Joined: Dec 09 2018
Member No: #3763
Location: Stockdorf
I have measured the noise the way you did and the DB were around 75/76 at 100 km/h.

I had the impression that the loudest "source" were the tyres (Hankook actually), not the engine...
1 User said Thank You to Fraunie for this Post :
 gkirkov (31 May 2020)
mtee   
Fri May 29 2020, 09:35pm
Joined: Oct 29 2014
Member No: #1924
Location: Kuopio
My car had wind noise from front door window. The window rose just few mm higher than it should. I discovered this simply by opening and closing the window and stopping it with the button just before it reached its closed position. I marked the noise-free position on the glass and A-pillar and then had the window adjusted by a Citroën garage according to the factory instructions.

After the job they told that the correct position quite exactly coincided with my marking. No wind noise any more.
4 User said Thank You to mtee for this Post :
 C6Dave (30 May 2020) , Jas16 (31 May 2020) , Radox (31 May 2020) , gkirkov (31 May 2020)
ChrisW   
Sun May 31 2020, 11:36am
Joined: Jun 18 2013
Member No: #1335
Location: Surrey
I've researched interior car noise and it appears that, at cruising speeds, road noise is the biggest factor and much of this is transmitted directly through the metalwork. Adding sound insulation may help a bit but, as the C6 is already well-insulated, the effect may be small.

My solution was to buy 17" alloys (ebay £150, from one of the sportier Volvos), and fit 225/60R17 tyres. This gives an extra inch of rubber between the wheel rim and the road, about 20% more rubber. Plus 2cm narrower than the standard tyres, which also makes for a quieter and smoother ride. The effect was amazing. Rolls Royce comfort - both noise and ride quality. Handling was unaffected. The speedo reads spot-on rather than over-reading by a few MPH.

Fitting was easy but you need to do your research to make sure that the bolt spacing, centre-hole diameter and offset are correct. I needed to buy special spacers and longer bolts, again from ebay.

I chose Maxxis Premitra HP5 tyres because the sidewalls have only one ply, so are more flexible. I told my insurance company before making the change - no increase in premium. If anyone wants to buy a set of 4 original Atlantique wheels, please let me know!
2 User said Thank You to ChrisW for this Post :
 Radox (31 May 2020) , gkirkov (31 May 2020)
Radox   
Sun May 31 2020, 09:21pm
Joined: Aug 27 2019
Member No: #4044
Location: Bad Bergzabern
mtee wrote ...

My car had wind noise from front door window. The window rose just few mm higher than it should. I discovered this simply by opening and closing the window and stopping it with the button just before it reached its closed position. I marked the noise-free position on the glass and A-pillar and then had the window adjusted by a Citroën garage according to the factory instructions.

After the job they told that the correct position quite exactly coincided with my marking. No wind noise any more.


Thanks, will give it a try!
Radox   
Sun May 31 2020, 09:37pm
Joined: Aug 27 2019
Member No: #4044
Location: Bad Bergzabern
ChrisW wrote ...

My solution was to buy 17" alloys (ebay £150, from one of the sportier Volvos), and fit 225/60R17 tyres. This gives an extra inch of rubber between the wheel rim and the road, about 20% more rubber. Plus 2cm narrower than the standard tyres, which also makes for a quieter and smoother ride. The effect was amazing. Rolls Royce comfort - both noise and ride quality. Handling was unaffected. The speedo reads spot-on rather than over-reading by a few MPH.


Do you think it will also work with 225/60/R18 tyres? I don't want to change my Atlantique 18 wheels.
gkirkov   
Sun May 31 2020, 10:41pm
Joined: Jul 12 2019
Member No: #3981
Location: Bulgaria, Sofia
I think you'd do better with 225/55/R18 which gives you 14% increase in sidewall and +3.7% in circumference, compared to +23% sidewall and +3.4% circumference for 225/60/R17. For the purpose of comfort I'd personally go with 245/50/R18 to gain +11.6% sidewall and +3.4% circumference and basically keep the safety, but I'm worried how it will affect the million other things about this car's complicated suspension... So I actually went with stock size.
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