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Thread: Reducing noise inside my Mk4

  
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    Reducing noise inside my Mk4

    I own a Y2000 2.0 DTi for some months now and have done some mods myself like heated front seats, installing foglights etc.
    I've also spend some quality time to have the audio as good as it is now (Becker 7944, Rockford Fostgate amp etc).
    So all in all I am pretty happy with the car.

    But now I am wondering what can be done to reduce some (or most) of the noise coming from the diesel engine (or engine bay) and, when possible, what can be done to reduce the noise coming from the tires etc.

    As said, I have the 2.0 DTi (DTH) motor and as far as I can see there is hardly any sounddeadning of isolation stuff behind the firewall (not in the enginebay and not under the dash).

    The same goes for the noise coming from the wheels, tires, street (whatever )

    Some info about the car whih might help...
    It's running on 205/50/16 Conti SportContact tires
    All 4 doors are damped with mats and are as dead as hell

    I couldn't find a topic about this subject but I do hope that one of you guys or girls have some experience with this.

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    On a standard (petrol) Astra G all noise is well suppressed EXCEPT for tyre noise. Wide, low profile, tyres make it even worse.

    Check around the tyre sites on the web, like MyTyres, and research the noise levels for different brands of tyre. Conti/Continental are one of the quieter brands, though!

    I've never used it but some ICE can be specified with noise-cancelling - sophisticated electronics which detect the frequency, phase and volume of external noise and add a cancelling phase to sound being output from the ICE.
    Maintains:- Vectra Design 1.9CDTi
    Drives :- Hyundai Santa Fe


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    In the UK items like Dynamat and Brown Bread are used to suppress the noise. This is most certainly a mod that I will be doing to my car. It can be obtained by any good ICE stockist easily. But can be very expensive if your going to mat the car like I intend to.
    Its a jam thing

    Haec credam a deo pio, a deo justo, a deo scito?



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    Certainly look at sound deadening the cabin.

    Basil has done his VXR (roof included)

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    Quote Originally Posted by Ruperts Trooper
    On a standard (petrol) Astra G all noise is well suppressed EXCEPT for tyre noise. Wide, low profile, tyres make it even worse.

    Check around the tyre sites on the web, like MyTyres, and research the noise levels for different brands of tyre. Conti/Continental are one of the quieter brands, though!

    I've never used it but some ICE can be specified with noise-cancelling - sophisticated electronics which detect the frequency, phase and volume of external noise and add a cancelling phase to sound being output from the ICE.
    Well supressed, not a chance! Vauxhalls uses minimal amounts of soundeading and noise absorbtion in the Astra G and the Astra H. While in keeping with other cars in there segment if you have a look at the likes of the luxary cars and you get the idea of just how much more sound absortion and deading is used. Cars like the RR and Maybach soundeaden the cabins in there entirety and for good reason.

    Noise cancelling electronics are not widely used in an In car environment and for good reason to achieve any form of noise supression in a car you would need to spend thousands to get some decent electronics to deal with all the different frequecies.

    In motor vehicals you have various forms of noise. Panel vibration is probably the biggest, follwed by Road noise and engine noise and lastly ambient noise i.e. Wind noise etc.

    The best and probably the only way to reduce panel vibration is firstly soundeaden the panels using the likes of Dynamat Extreme, Diamplfier pro, Brown Bread etc. (Flashing tape is designed for house roofs so leave it there please. Yes it is better than nothing but still that is not saying much). Particular attention is needed on the Firewall (interior) and the wheel arch area. But the doors and the floor are massively important in this regard. The bonus of this method is that it reduced road noise and ambient noise to a certain extent anfd it keeps the car interior cooler.

    Next up time to tackle ambient noise and road noise (the sound deading above helps reduce this noise by up to 12Ddb in some applications I have seen but using soundmatting or acoustical sludge has a massive effect as well). This can easily reduce ambient noise/road noise by up to a further 4-5db. For top makes look at the likes of Overkill/Overkill Pro, dynaliner Spectrum sludge by second skin. BTW the roof area is mostly the source of wind noise but panel vibration due to a good aftermarket system means that sound deading will also help.

    Lastly the major inlets for engine noise are the firewall and the bonnet area. In this regard Motormat, Dynaliner and hooliner are top makes and one or the other will all help.

    Different road tyres do have an effect on road noise but few manufacturers quote actual figures on this and a tyre on one car can react total differently on another car/make. So it is pretty much a difficult task to gauge which tyre is best. Bridgestones seem to be excellent at low noise but some tyres are marketed as low noise models.

    And one final way to takle road noise not mentioned above can be achieved by removing the wheel arch liner and installing a specifically designed matting on top of the arch liner. The make of the stuff eludes me at this point but there is stuff desgined for the G and boy does it work in a huge way. For example look at various top end cars a la Lexus, Mercedes and BMW that have material arch liners for this very purpose.

    So then how much does it cost. Well to do a G properly you would need about 3 to 4 bulk packs of dynamat and possibly 3 sheets of overkill. Gains in my old car (Astra G) using just the Dynamat was 12.18db. In the VXR using dynamat Extreme (3 bulk packs) and 4 sheets of Overkill and 2 sheets of overkill Pro gains have been massive 19db reduction. I will be doing the bonnet at a future date once BBG get my dynaliner in stock.

    Total cost to me on the G was less than £150 (I got most of it free,) on the VXR I got the stuff cheap yet again. What I thought I paid was way off the mark in fact it was two and a half times less than I thought. I will not mention the price as they were a special discount to me. Paying retail prices you could be looking at up to £500 to do a complete job. Remember you do not have to do everything to achieve gains, but decision is yours how much you use as well as the make you use.


    So botom line is the above might not sound like much but, trust me little noises in the cabin like loose change suddenly takes on new meaning. Do it once and you will be doing it in all future cars. Shame you where not at the Christmas do as I would have demonstrated it to you. Jimmy C, MatG and M40C00 all got a little demo of just how well it works and what can be achieved.

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    Quote Originally Posted by BasilD
    Astra G and the Astra H.........RR and Maybach
    You're right, but that's not a realistic comparison!!!

    On my Astra G (CDX) tyre noise is the main sound source, by a very long way, on both OE Michelin XH1 and replacement Goodyear NCT5.

    Astra G engine/transmission noise is well below Focus / Golf levels, or was 7 years ago when I evaluated them.
    Maintains:- Vectra Design 1.9CDTi
    Drives :- Hyundai Santa Fe


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    Thanks guys for all the interesting comments on this subject.
    Esspecially the contribution of BasilD is very interesting.

    One thing was not taken in consideration and that is the fact that I am driving a diesel
    I know from my own experience what a HUGE difference it is to have a G with a petrol or a diesel engine.

    Now forgive me this question but, as a start, what is the first thing to do. Which mod will give the most improvement in terms of reducing engine noise coming from the engine bay ?

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    i dnt know if this is exactly true, but i put a bonnet insulater in my car and it seems to have killed a little bit of noise
    The car in front is my astra!!!!!!!!!!!!!!!!

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    Quote Originally Posted by Ruperts Trooper
    You're right, but that's not a realistic comparison!!!

    On my Astra G (CDX) tyre noise is the main sound source, by a very long way, on both OE Michelin XH1 and replacement Goodyear NCT5.

    Astra G engine/transmission noise is well below Focus / Golf levels, or was 7 years ago when I evaluated them.
    True, hence me saying in there segment. But the point I was making was that they are not well soundeadend not by any strech of the imagination. Oh and as for the Maybach just shy of two months back I sat and watched as a certain tuner took the car apart and added extra soundeading to the car. 5 bulk packs later, even more sound mats and wat was a quite car became something in which you would probably hear a pin drop while the car was doing 120,

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