Just thought I'd give an update as I haven't for a while. I did ad-hoc sound deadening bits at my own pace.
I did the final rear wheel well some weeks ago, so thats all 4 done.
I also did half of the boot at the rear with 2 layers of dodomat, it's quite thin stuff so the big insert still fits back in the same place and is hardly raised. I didn't want to cover the battery.
Regarding the bonnet, my previous DS9 had the same size engine, albeit 225hp rather than 180hp and when I fitted one of these to it
https://www.dodomat.com/products/dodo-bonnet-liner the engine was almost inaudible after that minute or 2 when the higher revs subside. You really had to listen for the engine at tickover. The mat covered it all and is 10mm thick.
With the less comprehensive alternative in the C5X, pics above a few posts ago, I think it had some effect, but perhaps not as much as I'd like. I think I'm inclined to put another layer on first rather than go for the thicker mat. I'll think about it. It could be the bulkhead isn't as soundproofed as the last car? Obviously the difference I'm after isnt a comparison at tickover but say at motorway speed when the difference will be more stark.
In my opinion there are 2 more things left remaining, and these perhaps despite the improvements I have done thus far could make the most difference at the end of the day. Im still thinking noise from the road is higher than it should be and far more so than the DS9.
1) In the DS9 it had a plastic undertray like all cars have, mainly to protect the undercarriage and to aid aerodynamics. But this came in kinda 2 halves on top of each other, both trays with lips with the edges end to end, so the bottom tray face up and the other face down on top. This created a little gap inbetween of about 2-3cm. In the DS9 i did put a fair bit of sound deadening in here, hardly complete but enough to make a difference and stop it being just one big resonating drum.
In the C5X it's just 2 single plastic undertrays per side, a long one from the front wheels to about 2/3's of the way to the rear wheels and then another for the remining 1/3rd. Unlike the DS9 it isnt double skinned. I think if i dropped this down and just put a single thin layer of dodomat on top it'd make a lot of difference but its awkward to get to so I've paused on it. With a lift like in garages it'd be a lot easier.
2) The doors are like big drums to the tap test and I've looked a bit and decided I don't want to be invasive and try and take the door cards off. At the bottom of the doors are the plastic surrounds and they go down and under the car....and rattle a bit. I've found on the front doors behind the circular 4cm plasters (took em off with tweezers) are 2 nuts, I think if i take then off the plastic will come away (going to try this tomorrow). There is definitely a circa 6-8mm gap between the plastic and the metal and I want to fill that. I think what happens is the noise enters through the plastic and then travels up the door. If I can reduce this at source then it should improve things.
After reading all this back I do think perhaps the undertrays are going to be the big win. They must cover about 3sqm of the undercarriage in total and any slight improvement to something of this size should make a marked difference.
