Cobra resonated exhaust drone problem

[D350z]

I have a 2007 Azure roadster at 34k miles and have just had to have a new exhaust back box (split and difficult to weld apparently). Anyway I decided after reading reviews here and watching countless youtube vids that I would get a 3" stainless resonated Cobra system including the Y piece. I had it fitted okay and it sounds great, much louder than stock, when giving it some throttle but it has a deep annoying drone between 2000 and 3000 revs under slight load. Motorway driving has become tiresome. Is there anything I can do to solve the issue? All things considered. Soundproofing, changing an exhaust component, selling the car etc. 

[reeceybeaney]

I always thought my resonated cobra was perfect for daily driving, whilst still producing a gorgeous note.

Maybe in the roadsters you can hear the exhaust more predominantly but there's not really a lot else you can do other than reverting back to a standard oem exhaust?

A Milltek system is one of the quietest just in case thats a possibility?

[D350z]

Thanks Reecybeaney. Mine sounds like a big hollow box with a deep drone. Yes the top notes and raspiness are good but when the throttle opens up just a bit the drone switches on.

[Mark350Z]

I have the same resonated cobra setup, albeit with a JapSpeed Y-Pipe but get the same drone as you mentioned between 2-2.5k rpm. I found it droned with the standard Y-Pipe on as well. Not sure there’s an awful lot that can be done to cure it. I tend to stick it in 5th if I’m doing around 60mph which is just above the drone area or if I’m on the motorway I tend to be going quick enough to be able to put it in 6th and not notice it. 

[davey_83]

It'll get quieter once the internals are all coked up nicely.

[reeceybeaney]

6 minutes ago, davey_83 said:

It'll get quieter once the internals are all coked up nicely.

True that, then you'll go buy some Art Pipes 

[Randy_Baton]

I've got the same issue, I quietened mine down a bit with dynamat all over the rear end and then put some carpet underlay under the boot mat. I've got 1 layer of basic foam carpet underlay that i brought for a few quid from a carpet shop and then my friend had some of the proper rubberised sound proofing stuff left over from his house so I chucked that in as well. The 2 layer of underlay mean my tonneau cover is well wedged in now 

[D350z]

Thank you Randy. Soundproofing is my next step. It seems a shame that resonance can’t be dealt with in exhaust design. The lovely top notes are fine it’s just the boom that’s the issue.

[Stevie-Boy]

I haven't noticed that with mine, same car and same exhaust system. I've always thought the sound was very well behaved but what might sound reasonable to me, could be excessive to you.

[HiddenWomble]

I have the invidia gemini which sounds better than stock when you stamp on the noise peddle but is also nice and calm when cruising round town or on the motorway, so i vote you change exhaust before you sell the zed!

[D350z]

On 18/07/2018 at 17:55, Stevie-Boy said:

I haven't noticed that with mine, same car and same exhaust system. I've always thought the sound was very well behaved but what might sound reasonable to me, could be excessive to you.

Thanks, overall I'm happy with the sound quality and the volume at all revs except between 2000 - 2600 rpm. Thats when it booooms. I might just need to change one box rather than the whole system. I've done 1k miles now and it is damping down a bit now that it's coking up  for your reply

Edited July 20, 2018 by D350z

[D350z]

On 18/07/2018 at 20:12, HiddenWomble said:

I have the invidia gemini which sounds better than stock when you stamp on the noise peddle but is also nice and calm when cruising round town or on the motorway, so i vote you change exhaust before you sell the zed!

Thanks for this. I might just change the back box for the Militek or Invidia and leave the Y pipe, front silencer etc in place. I'll check out my options. 

[davey_83]

The systems are not interchangeable sadly fella.

[D12TEE]

tbh, i get the problem just from some cobra decats, but i think its just one of those things you have to expect, top end noise is lovely, but its the 2-3k that isnt perfect.

[Dave6188]

I had the exact same issue with the resonated Cobra in my coupe, the drone was horrendous and echoed/boomed around the cabin, got even worse when climbing hills etc. My end solution was going back to stock because I hated it that much !

 

I ended up opening my stock backbox up and removed the sound deadening then welded it back up, it sounds just right to me now, bit more V6 rumble and no drone so I'm happy. 

Edited July 23, 2018 by Dave6188

[D350z]

23 hours ago, Dave6188 said:

I had the exact same issue with the resonated Cobra in my coupe, the drone was horrendous and echoed/boomed around the cabin, got even worse when climbing hills etc. My end solution was going back to stock because I hated it that much

Yep. It's driving me mad too. £650 wasted  I'll either go back to stock or have the inline silencer section (resonated) changed for something more substantial. The drone is shocking and I suppose if the Cobra system sound was good they could charge more for it. 

[nissanman312]

10 minutes ago, D350z said:

Yep. It's driving me mad too. £650 wasted  I'll either go back to stock or have the inline silencer section (resonated) changed for something more substantial. The drone is shocking and I suppose if the Cobra system sound was good they could charge more for it. 

Maybe get some extra silencers welded in 

[hawker1986]

We had a Cobra on our Zed for about 4 weeks, drone at cruising speed was terrible, changed it out for a Miltek. Not sure how people live with them.

[D350z]

27 minutes ago, hawker1986 said:

We had a Cobra on our Zed for about 4 weeks, drone at cruising speed was terrible, changed it out for a Miltek. Not sure how people live with them.

I certainly can't live with the Cobra. What sounds better, Militek or stock?

[D350z]

On 20/07/2018 at 21:23, davey_83 said:

The systems are not interchangeable sadly fella.

Thanks. Am I right in thinking I can keep the Cobra Y piece and then just swap out the back two pieces for a decent exhaust?

[davey_83]

Yes fella, y - pipe dimensions are all the same. You'll have no problem selling in the Cobra system via the forum matey. I'd suggest the miltek center and rear silencer system as it's a tad louder than stock from what I gather.

 

Nice big rear silencer and looks like this.....

https://www.ebay.co.uk/itm/miltek-exhaust-Nissan-350z-/132704195820 

Edited July 25, 2018 by davey_83

[SHEZZA]

This is the reason I went for the invidia Gemini as no drone with it. But as davey says as you’ve got the y pipe your next best bet I believe would be the miltek as you can buy that from the y pipe back. Then sell the cobra on the forum. 

 

https://www.tarmacsportz.co.uk/milltek-sport-nissan-350z-3-5-v6-03-10-y-pipe-back-exhaust.html

[colesl4w]

On the flip side I had the milltek and found it to be genuinely silent. It took away the fun of the car for me. Sold it to a guy who paired it with decats or HFCs and it sounds fantastic with them though. I now have the ark grip - absolutely  love it but it may be a tad too loud for your ttaste. If I were you I would sell the whole thing and go with the inviida gemini - you're 100% guaranteed to be very happy. 

[D350z]

39 minutes ago, colesl4w said:

On the flip side I had the milltek and found it to be genuinely silent. It took away the fun of the car for me. Sold it to a guy who paired it with decats or HFCs and it sounds fantastic with them though. I now have the ark grip - absolutely  love it but it may be a tad too loud for your ttaste. If I were you I would sell the whole thing and go with the inviida gemini - you're 100% guaranteed to be very happy. 

Fabulous advice- Thank you

[colesl4w]

8 hours ago, D350z said:

Fabulous advice- Thank you

No worries! I know how frustrating it can be to find the right sound for the car - it can make or break your love for the car entirely! You'll sell your cobra no problem and only lose a little bit of money on it. Make sure to post in here with an update once you've got everything sorted!