Car sound insulation help

I have few very long journeys to do this summer and as my car suffers from a lot of road noise I would like to add some sound insulation to my car before I go. I don't want bitumen based stuff like Brown Bread or flashing tape as I expect the car to be left for extended periods of time in very hot environments and would rather avoid any chance of asphalt smell or melted goo from sound insulation on the floor of my car.
I gave a lot of thought to Dynamat and other butyl based stuff but since I would need ef loads of it I simply can't justify the cost.

Which leaves me with two "ghetto sound proofing" possibilties:
- Dual layer of polymer-based, asphalt-free, high density synthetic membrane as used on floors ( such as http://www.customaudiodesigns.co.uk/soundproofing/t50.htm)
- Open cell acoustic foam, or as it's commonly known - a camping mat. With optional extra layer of alufoil faced laminate underlay

Does anyone have any experience with the above products or have any suggestions of how to cheaply but successfully sound proof my 'mera to Accura standards.

You can get that plastic foil-backed loft insulation from B&Q, it's much cheaper than the dedicated car stuff and looks like it's the same product.

Carpet underlay works well too, you just need to glue it on

just turn the stereo up...... have u had a look on ebay for bulk packs of dynamatt?
sorry I can't really helpist this other stuff your thinking about heavy? what are you doing floorpan and doors? is weight an issue?

k3v said:

is weight an issue?

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floorplan, boot, boot sidepanels and doors. Floor and boot is obviously most important. At the moment floor is resonant like a steel banjo. I think 5-10 square metres (30-60 square feet) ought to be enough, weight wise, at 5kg per square metre it would be between 25 and 50kg extra weight, which I think is survivable if it is to have proper sound proofing effect....

B&Q loft insualtion for sidepanels and doors sounds like a great idea, light, waterproof, relatively trouble free even if it becomes loose. Unless it's noisy on it's own - as in - swishy like a plastic bag or something..

Aquaseal or Marley sealing tape from B&Q/Homebase/Screwfix is practically the same as dynamat but a fraction of the cost. I did the floor of the MR2 with it and you definitely can't smell anything.