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Discussion Starter #1 (Edited)
I have a stage 4.25 car with full AC speedtech system with catless downpipes. I love my exhaust and the noise it makes. It is however quite noisy and I want to be able to do longer journeys and to have my kids in the back.

After a lot of driving, I have a feeling my ears ring afterwards and this is only going to be worse in the back of the car where my bambinos go. Now whilst I am learning to drive around the drone / max noise, there are a lot of times this is unavoidable.

Before trying to silence the exhaust, I am thinking I will install sound deadening material under the rear seats, firewall, side panels, boot floor and boot lid.

If I can do this ok, I will go onto do the same with the driver doors, probably as part of audio upgrades.

Having researched a fair bit, I see Andy's advert abour reducing drone, but from most of the threads where people are installing this, the benefits seem to be improved audio, reduction in road noise and reduction of gearbox noises. I need reduction of exhaust decibels.

Anyone any experience of this? Should I expect noticeably reduced exhaust noise within the cabin if I fit sound deadening material?
 

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Simple answer; no.

I've got a 4.25 and have deadened the rear seats, sides and boot. Hasn't made a noticeable difference to exhaust drone, just reduces the mechanical noise a bit. If I wanted to reduce the exhaust noise, I'd change exhaust.
 

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I would suggest that a full back end sound deadening job would 'take the edge off' an exhaust drone but there is nothing like going from non-res to res for example.

The skinz I supply is 50% thicker than most on the market and nearly double dynamat extreme but still it's not a fix! just an improvement :thumbsup:
 

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Discussion Starter #4
I did a bit of reading on GTR Life and there was someone that used a mix of the skinz / dynamat type deadener, which is targeted at reducing the vibration and mechanical type noises but also used a Second Skin Audio product called Luxury Liner Pro. This luxury liner pro is intended to shield against air borne noise signals, eg, exhaust noise and reported a great improvement.

Is it possible that using a specific airborne targeted shield (in addition to the usual sound deadener) I would see better results for reducing exhaust noise?

In terms of what I want to achieve, I don't want a quiet exhaust. I love the way my GT-R roars and I don't think it is overly offensive - I just don't want to damage my kids hearing in the process or have an unusable car for the family. Taking the edge off might be enough (or they can wear ear defenders...)
 

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If you're in to doing stuff to the car yourself then I really recommend using some lining product in your car. It's an easy, Sunday afternoon job and makes the car feel much more refined. I found I could have proper conversations at motorway speeds much easier too.
 

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I've tried some of this sound proofing sheet on my last GTR, similar to the Luxury Liner Pro. Basically its a closed cell foam and I bought it from a UK company specialising in sound proofing. After adding it over the whole back area and boot area, it once again, took another edge off the noise. Probably similar to the sound deadening but was quicker to install with bigger sheets and easier to cut. I kind of regretted it slightly then and found myself opening the window more to hear the awesomeness of downpipes and full exhaust.

It wasn't cheap either to do the whole lot in liner. I was however only using 2mm silent coat and not Skinz 3mm sheets for the sound deadening.


I did a bit of reading on GTR Life and there was someone that used a mix of the skinz / dynamat type deadener, which is targeted at reducing the vibration and mechanical type noises but also used a Second Skin Audio product called Luxury Liner Pro. This luxury liner pro is intended to shield against air borne noise signals, eg, exhaust noise and reported a great improvement.

Is it possible that using a specific airborne targeted shield (in addition to the usual sound deadener) I would see better results for reducing exhaust noise?

In terms of what I want to achieve, I don't want a quiet exhaust. I love the way my GT-R roars and I don't think it is overly offensive - I just don't want to damage my kids hearing in the process or have an unusable car for the family. Taking the edge off might be enough (or they can wear ear defenders...)
 

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Discussion Starter #7
That's interesting Andy and thanks for your PM - will think on it. I have found a UK company that supply sound proofing material for your house and they offer a 15mm sheet that is intended to reduce noise, which I would assume exhaust is classed as.

I was considering getting regular proofing (eg the skinz you provide) and doing the boot, bulk head and rear cabin and then fitting a big piece of this 15mm closed cell noise diffuser in the boot, ontop of the skinz but under the carpet. This stuff suggested a reduction in noise of 50db. I dont need that (and wouldnt get it in a car, particularly with limited coverage) but it should be good for reducing a handful of DB's that come from the exhaust. Assuming this doesnt need to be stuck down, I can remove it if I am going for a hoon and make sure atleast one sheet of it is in for family days out.

Does that sound logical?
 

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Dynamat Xtreme for reduce vibration, so decrease sound resonance. This is relatively ineffective to deal with drone due to large amount of panels could be involved in the vibration and natural frequency could vary at different spot of the car. The dynamat xtreme is more a damping membrane (reduce the sound amplitude) rather than altering the car panel's natural frequency. However, the additional mass of the material does affect the panel's natural frequency. Dynapad is for noise absorption is more effective as it creates a barrier stopping the sound waves entering the car (by sound damping, reflection and dispersion), but it is heavy and not practicable for overhead, sloping and vertical surfaces.
 

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I would buy a couple of 100 cel race cats from AC and get them to weld them into the pipe, no loss in performance and take the edge off the drone and less fuel smell, I bought the Fat Matt from R35 for under the seats and its a noticeable improvement in road noise and tyre noise (rear seats)
 

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