A mate has just purchased a Z32 TT Auto and is being driven mad by the droning / drumming in the cabin from the exhaust, so far he's changed the rear mufflers and removed and fitted a new front muffler behind the cats, nothing has made any difference, anyone got any experience in this area and can maybe offer some advise, Not sure if the auto may have something to do with it but it's usually at 2000 revs regardless of what gear it's in, Could the rear hatch be allowing noise in, would Dynamat help. Any ideas welcome.
I have the same problem and from reading other threads it is entirely the exhaust systems fault. A 2.5 inch system is supposed the be a lot better than a 3 inch system. Make sure he has a H pipe (or X pipe) or one of those pipes that joins the two sides. There are members running big sports systems that don't have this problem so it is possible. Apparently using the right mufflers is important. Since I'm not ready to change my system yet I'm going to go down to Clark Rubber and buy some sound deadening foam and fit it to the boot. This should make big difference. I had to transport a foam mattress the other day and couldn't believe how much quieter it was in the cabin!!!.
Hi had the same problem at about 90 to 100 kph when I changed the two stock rear mufflers to sports units so then changed the forward resonator for one double the length and also it was fiberglass packed. Difference on my n a is huge
I have 2 1/2" from the dumps through to just before the cat where it merges into a 4" od after the cat it has a short resonator then 4" ID to a muffler. I think its not too loud, am yet to find out what the boys in blue think - 4000 kms and no issues so far (touch wood) - I have been into the local exhaust shop and they wont tell met its legally quiet enough but will say they have mad plenty of systems louder that have no issues (yep covering their arses but I cant blame them). No real drone I have driven to perth in it twice now (420 kms each way) and the $80 stereo had no issues overpowering the exhaust. IMO the quality of the mounting has as much to do as the construction. also the actual location of the tip can have a huge effect, my old bluebird had quite a long tip that lost a lot of its in cabin drone once we removed 1 1/5 inches from it.
Have a look at the UAS centre X pipe muffler: http://www.nismo.com.au/ Look under 300ZX exhaust systems to find it! A lot of people swear by them for reducing drone! You can also get a cheaper Magnaflow version of the same sort of thing. Something like this: http://www.magnaflow.com/02product/shopexd.asp?zone=main&id=9095 You just need to get the one that is the closest dimensions to the UAS version to be sure it will fit under the Z ok!............& the right pipe diam (remember US measure to inside of pipe not outside as we do here in Aus! eg Aus 2.5" = US 2.25".......If I recall correctly??)
A good fix for this issue is to keep a couple of pigeons in the cabin whilst driving. All the flapping of wings ensures your mind is not focused on the droning noise.
Same issue I have the same problem with mine - I have 2.5" from the stock dumps, thru 2 high flow cats, into a UAS centre muffler - then up to 3" to Cannons on the back. Still drones like anything, I need to get sorted and get some proper mufflers for the back... The other thing I had suggested, is where the pipe steps up from 2.5" to 3" could be the issue - as it quitens down at around 3000rpm - the extra flow could be stopping the sound echoing in the 3" pipe....not sure how accurate that idea is though! To fix the 90-110kph drone I fitted a NA rear end Worked perfectly on the motorway!
if thats true, why is it? the engine is pumping the same amount of air at any given revs, so the exhaust should be the same volume at any given revs?
No its just not that simple. Its an accoustics thing altho the gasflow influences things. To do with accoustic resonant frequencies. Its a black art. Valancing (x-over or "H"-pipe) the system is crucial along with where its valanced to piss drone off. I have an NA. 3" dumps from tubular extractors, thru a pair of cats and then 2 x 3" larg(ish) diameter resonators about 300mm long Then onto 2 x 3" Lukey sports mufflers (side in/ center out) at the back. There is a 2.5" valance pipe just behind the diff. The system is remarkably quiet and dignified at any sensible throttle opening below about 3500 to 4000 when it gracefully and progressively breaks into a glorious V6 growl which just gets growlier as the revs/power rises! NO drumming or droning in the cab at any revs tho!!! Amazing really for a twin 3" system on an N/A. Even the zorst shop guys who did some repairs commented on the particularly cool sound of it. Its prolly more luck than good management that its so quiet at everyday driving around levels! Id guess it was a twin system off a TT. I reckon it would sound sweet as on a TT. L8r E
