Waffles Posted December 17, 2017 Share Posted December 17, 2017 It's been a couple of months since I took the plunge and upgraded my '08 350z to Berks HFC and Cobra exhaust + Y-Pipe. With it all added and the engine re-tuned it's a joy to drive. But that drone.... I do a lot of motorway driving, and 2000-2500 revs there is some serious cabin noise. Trawling through the forums lots of people say that the drone fades as the carbon builds up, but no such luck (at least so far). I know exhaust notes and noise is a very subjective thing, so I've tried to get some sort of measurement. Here's Android's guess at the noise levels in 6th doing 60mph: dB readout Not the most accurate measuring device in the world, but hopefully gives you a better idea. As for the frequency, it's the 125Hz range that's the culprit: Frequency readout So a question to all the exhaust gurus out there: What are my options? From what I've read so far: 1. Swap back to the stock cats 2. Swap out the Cobra to another exhaust 3. Sound proof the **** out of the boot 4. Ignore it and eventually it will get quieter/I will lose enough hearing to ignore it :-) Hard to answer without being subjective I know, but what would people recommend? Or if someone is in Hampshire/Berkshire area and fancies a winter meet-up? Quote Link to comment Share on other sites More sharing options...
Irn Bru Posted December 17, 2017 Share Posted December 17, 2017 Are exhaust bungs an option for your system ? Quote Link to comment Share on other sites More sharing options...
davey_83 Posted December 17, 2017 Share Posted December 17, 2017 Resonated or non resonated system? Quote Link to comment Share on other sites More sharing options...
Waffles Posted December 19, 2017 Author Share Posted December 19, 2017 On 17/12/2017 at 19:46, Irn Bru said: Are exhaust bungs an option for your system ? None that I've seen. I had a chat with the nice folks at Cobra but they didn't suggest anything like this, so I'm guessing it's not an option On 17/12/2017 at 20:33, davey_83 said: Resonated or non resonated system? It's the resonated version. Quote Link to comment Share on other sites More sharing options...
Bigjimg Posted December 19, 2017 Share Posted December 19, 2017 Have a watch here, my car at 70mph mostly with Cobra system including high flow Cobra cats. No real drone at all mainly road noise. https://www.youtube.com/watch?time_continue=185&v=3TTS9B-eG9M Quote Link to comment Share on other sites More sharing options...
Erni902 Posted December 19, 2017 Share Posted December 19, 2017 Just my 2 pennies worth. I have a decatted Nismo system so not quite the same as your setup. The drone for me is not too bad I don't really tend to notice it. The issue I have is that when I have my daughter in the car she talks quite softly and I end up getting out the other end having agreed to cinema trips and toys and days out etc. and its costing me a fortune. To that end I've been looking at soundproofing and what I am planning is to use something like dynamat across the entire boot floor and the transmission tunnel (although I will probably end up doing the entire floorplan whilst the carpet is out). This will stop the vibrations/rattles etc being transmitted around the shell. The next step is to add a layer of foam to absorb soundwaves. Then on top of this I am looking at some sort or rubber type sound blocker. Not entirely sure if this will cut out the specific frequencies I'm after but hopefully should make a difference. I have experienced this in another car and did the above 3 phase sound deadening and it did make such a difference so Im hoping I will notice the difference in the Zed aswell. Hope this helps mate. Quote Link to comment Share on other sites More sharing options...
slipstream Posted December 19, 2017 Share Posted December 19, 2017 If I was you waffles i would go for option 1 and then sell me your berks Quote Link to comment Share on other sites More sharing options...
Waffles Posted January 3, 2018 Author Share Posted January 3, 2018 On 19/12/2017 at 14:11, Bigjimg said: Have a watch here, my car at 70mph mostly with Cobra system including high flow Cobra cats. No real drone at all mainly road noise. https://www.youtube.com/watch?time_continue=185&v=3TTS9B-eG9M That sounds really nice. I tried to take a similar video of mine for contrast, but it really didn't pick up the low noise at all. Hopefully there will be a meetup at some point that I can get to; guess there's no substitute for hearing it in person :-) Quote Link to comment Share on other sites More sharing options...
Waffles Posted January 3, 2018 Author Share Posted January 3, 2018 On 19/12/2017 at 18:24, Erni902 said: Just my 2 pennies worth. I have a decatted Nismo system so not quite the same as your setup. The drone for me is not too bad I don't really tend to notice it. The issue I have is that when I have my daughter in the car she talks quite softly and I end up getting out the other end having agreed to cinema trips and toys and days out etc. and its costing me a fortune. To that end I've been looking at soundproofing and what I am planning is to use something like dynamat across the entire boot floor and the transmission tunnel (although I will probably end up doing the entire floorplan whilst the carpet is out). This will stop the vibrations/rattles etc being transmitted around the shell. The next step is to add a layer of foam to absorb soundwaves. Then on top of this I am looking at some sort or rubber type sound blocker. Not entirely sure if this will cut out the specific frequencies I'm after but hopefully should make a difference. I have experienced this in another car and did the above 3 phase sound deadening and it did make such a difference so Im hoping I will notice the difference in the Zed aswell. Hope this helps mate. Interesting to hear you've had some success in sound deadening. From what I've read elsewhere, deadening works to stop rattles but isn't so effective on lower dB noises like exhausts. I've already coated my boot in Dynamat and a little of the Dodo MLV with very little benefit. I'm guessing it will need to have the whole floor and boot with the thicker deadening stuff to really have an impact Quote Link to comment Share on other sites More sharing options...
Waffles Posted January 3, 2018 Author Share Posted January 3, 2018 On 19/12/2017 at 18:49, slipstream said: If I was you waffles i would go for option 1 and then sell me your berks It may well come to that. Well you can have first dibs ;-) 1 Quote Link to comment Share on other sites More sharing options...
Erni902 Posted January 3, 2018 Share Posted January 3, 2018 2 hours ago, Waffles said: Interesting to hear you've had some success in sound deadening. From what I've read elsewhere, deadening works to stop rattles but isn't so effective on lower dB noises like exhausts. I've already coated my boot in Dynamat and a little of the Dodo MLV with very little benefit. I'm guessing it will need to have the whole floor and boot with the thicker deadening stuff to really have an impact Yeah Im going to go the whole hog and make it nice and thick. Reason being Im going to embark on a project making the load space/boot bigger and will therefore get a complete custom carpet made up afterwards. As Im adding far more boot space this allows me to go slightly thicker with the sound deadening etc. Plus Im not that bothered by the weight of it as I will be removing a bit of weight anyway so shouldnt actually end up being much heavier. The way Nissan have put these cars together is ridiculous and massive overkill. Even the door to the 'glove box' is heavy as hell for what it is. Will be a slow project as not a priority but will update once completed. Quote Link to comment Share on other sites More sharing options...
GrahameJ Posted January 4, 2018 Share Posted January 4, 2018 (edited) I quietened mine down using Duralay 3mm laminate flooring underlay from B&Q. It's claimed to reduce sound transmission by 22db. In my JDM I took out all the boot plastics, and covered everything from the seats backwards, including the inner wings. I then used the original boot carpet as a template and glued two layers of the Duralay to that too, and still have some left. http://www.diy.com/departments/duralay-3mm-laminate-flooring-glueless-wood-flooring-underlay-7-5-m/551316_BQ.prd The roll covers 7.5 m², so will easily cover your boot and transmission tunnel. Cut to shape with some heavy duty scissors and glue it down with spray on carpet adhesive. Note - JDM models come with minimal sound deadening, and if you lift the carpet up it is painted metal underneath, so my efforts were mainly to overcome road noise from the rear tyres. The original JDM exhaust is quiet, and one reason I later bought the India Gemini dual exhaust system so I could hear it! Edited January 4, 2018 by GrahameJ Clarification Quote Link to comment Share on other sites More sharing options...
KyleR Posted January 4, 2018 Share Posted January 4, 2018 On 19/12/2017 at 18:24, Erni902 said: Just my 2 pennies worth. I have a decatted Nismo system so not quite the same as your setup. The drone for me is not too bad I don't really tend to notice it. The issue I have is that when I have my daughter in the car she talks quite softly and I end up getting out the other end having agreed to cinema trips and toys and days out etc. and its costing me a fortune. To that end I've been looking at soundproofing and what I am planning is to use something like dynamat across the entire boot floor and the transmission tunnel (although I will probably end up doing the entire floorplan whilst the carpet is out). This will stop the vibrations/rattles etc being transmitted around the shell. The next step is to add a layer of foam to absorb soundwaves. Then on top of this I am looking at some sort or rubber type sound blocker. Not entirely sure if this will cut out the specific frequencies I'm after but hopefully should make a difference. I have experienced this in another car and did the above 3 phase sound deadening and it did make such a difference so Im hoping I will notice the difference in the Zed aswell. Hope this helps mate. To be honest, mate, if you're gonna go that far with sound deadening, you'd be safer just swapping out the exhaust. Sell the Nismo and buy a brand new Milltek with the money. That way it'll be much much quieter and you won't have to rip the car apart. Quote Link to comment Share on other sites More sharing options...
Bullet Posted January 4, 2018 Share Posted January 4, 2018 From my experience most of the drones doesn't come through boot, Its the false floor behind the rear compartments. Quote Link to comment Share on other sites More sharing options...
Erni902 Posted January 4, 2018 Share Posted January 4, 2018 4 hours ago, KyleR said: To be honest, mate, if you're gonna go that far with sound deadening, you'd be safer just swapping out the exhaust. Sell the Nismo and buy a brand new Milltek with the money. That way it'll be much much quieter and you won't have to rip the car apart. For me this isn't even remotely an option. Personally I think the Nismo is the best sounding exhaust on a Zed. Not being biased because I have one, I thought this before I even had a Zed. The sound from the outside and with the windows down is just what I want. Stripping the interior won't be an issue for me as I enjoy doing it and Ive got to strip it anyway to make the modifications to the boot. 3 hours ago, Bullet said: From my experience most of the drones doesn't come through boot, Its the false floor behind the rear compartments. I agree, the boot is not the main location for the drone etc. which is why the whole car is being done. I'm going to strip the whole lot down to have custom carpet made up and modify the boot by removing the top half above the compartments. The inside of the compartments will also get the treatment to stop the sound resonating. Pretty much everything that is metal will be done on mine by the time I'm finished with it. Quote Link to comment Share on other sites More sharing options...
KyleR Posted January 5, 2018 Share Posted January 5, 2018 18 hours ago, Erni902 said: For me this isn't even remotely an option. Personally I think the Nismo is the best sounding exhaust on a Zed. Not being biased because I have one, I thought this before I even had a Zed. The sound from the outside and with the windows down is just what I want. Stripping the interior won't be an issue for me as I enjoy doing it and Ive got to strip it anyway to make the modifications to the boot. I don't disagree, I have a Nismo with decats too, plus parts of the interior stripped out to fit the roll cage, but I would never dream of trying to hide that noise. How about drive in 5th instead of 6th when it starts to drone, that way it's a nicer note Quote Link to comment Share on other sites More sharing options...
Erni902 Posted January 5, 2018 Share Posted January 5, 2018 6 hours ago, KyleR said: I don't disagree, I have a Nismo with decats too, plus parts of the interior stripped out to fit the roll cage, but I would never dream of trying to hide that noise. How about drive in 5th instead of 6th when it starts to drone, that way it's a nicer note Its only when the daughter is in the car, the rest of the time I have the windows down anyway. I do like your solution though Quote Link to comment Share on other sites More sharing options...
Paul667 Posted January 7, 2018 Share Posted January 7, 2018 I have Cobra HFC's and the full Cobra resonated system and my noise meter, when located near the cubby, shows up to 95 dB's at times!! I will try to get a video. When i Stand about a meter behind the car I get around 106dB @ 45000rpm....... however driving in traffic with light throtttle, the ICE and conversation are no different to most cars. but as we all know the ZED comes alive over 4.5K ......... conversation stops.......... and the ICE redundant:) Quote Link to comment Share on other sites More sharing options...
Cimanu Posted January 10, 2018 Share Posted January 10, 2018 Mine is a cobra non-res with motordyne ART pipes, no drone whatsoever unless up a hill at about 60. Usual speeds above 70 it's silent, just the road noise. Static test trackside it did 104.8db ART pipes really are worth the money! Quote Link to comment Share on other sites More sharing options...
EzeePzee Posted January 11, 2018 Share Posted January 11, 2018 On 10/01/2018 at 12:40, Cimanu said: Mine is a cobra non-res with motordyne ART pipes, no drone whatsoever unless up a hill at about 60. Usual speeds above 70 it's silent, just the road noise. Static test trackside it did 104.8db ART pipes really are worth the money! But then you have hassle with MOTs....? Quote Link to comment Share on other sites More sharing options...
Cimanu Posted January 12, 2018 Share Posted January 12, 2018 19 hours ago, EzeePzee said: But then you have hassle with MOTs....? Once a year to swap them over isn't so bad.. It's worth it to me. That's one of the pros for HFC though for sure, fit and forget! Quote Link to comment Share on other sites More sharing options...
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