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View Full Version : exhaust noise reverberation dampening



Davezj
15-02-2012, 02:32 PM
If your wrapped you whole exhaust in exhaust wrap tape would it make the noise that gets back into the cabin less, would it reduce the reverberation.

what do you think?

i am not thinking of performance gains just a bit of noise reduction.
especially at the 2500-3000 range when mine seems to boom, probably resenent frequencies and all that.

alan
15-02-2012, 06:53 PM
should quiet things down,it is insulation after all,but by how much is anyones guess. it will keep the heat in there too i would have thought

alan
15-02-2012, 07:00 PM
just a thought but the sympathetic frequencys that trigger the reverb,may be altered/reduced/dampened, i think it would be a suck it and see situation. you can get cheap tape/wrap at most bearing factors,its nomally for wrapping industrial equipment but i bet its the same as the stuff that an auto suppler would use and charge you double for

Davezj
15-02-2012, 08:29 PM
Yes I would assume the resonant frequencies would change once I wrap the exhaust, and that would also depend on how tightly I wrap it as well.

VR457
16-02-2012, 02:01 AM
Silent Coat in the boot (caraudiodirect / ebay) with a good damping mat on the top. The exhaust resonates the metal and your car is then an amplifying chamber for your ears....

That's what i'm going to do myself you see so no harm in suggesting to you too. Aim for £40 and what's left you can line the floorpan with. I have a post here on sound deadening that might come in handy.

VR457
16-02-2012, 07:28 AM
Or this?

http://www.ebay.co.uk/itm/Silencer-Db-Killer-Exhaust-Baffle-Bung-3-3-5-4-4-5-5-Fits-Jap-Tip-backbox-/220904019331?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item336ee7d583

wintertidenz
16-02-2012, 08:36 AM
There's always a louder exhaust noise at 2500-2800 anyway, I think that modified downpipes could get rid of that - however someone that has downpipes that aren't standard can confirm that.

Davezj
16-02-2012, 09:29 PM
I have a power flow one piece exhaust, 2.5" all the way through very small sports cat and 2 very small silencer and a small back box.
That is why it is so loud and reverberating. I would not have minded if it was rally loud on full WOT, but that is expected, it is annoying because it is reverberating at 40mph in 4th gear and 65-70 in 5th gear.

I don't want to replace it as it is a full stainless system. And quite expensive.

So changing the point at which the reverberation occurs would be a start.
I am considering getting one of the power sapping exhaust bungs.

VR457
16-02-2012, 10:31 PM
Say if you had a small reducer pipe at the exit, from 2.5 to 2 inch, about 8 inches long and drilled some holes in it, would it impede airflow too much? Im assuming that the holes will create alternate airflow paths thereby creating noise cancellation at some frequencies.

funkstardelux
16-02-2012, 10:35 PM
exhaust wrap on pipes can keep in wetness and damp..not problem on Stainless exhausts but mild steel is bad i've heard on skyline forums

Davezj
16-02-2012, 11:50 PM
This was something I had thought of with the rusting issue, turbo elbow and exhaust housing are steel and as such will rust, in my case but as that area get so hot in normal operation it will not be a problem.

Even if I had a full mild steel exhaust and wrapped the full length of it, would the hot of the exhaust gases heat the tape up enough to dry it out. You might have to leave the engine running for a couple of minutes after you reach you destination, to ensure the tape is dry before the engine stops.

It might be a bit tricky to wrap the turbo housing and elbow with out taking them off. All the exhaust shield will have to come off anyway. The front manifold and turbo housing should be relatively ok to do bu the rear will an arse to do.

But I will never know until I try it.

SGHOM
17-02-2012, 12:08 AM
Err??

If you want a quiet car.... why buy a loud one, make it louder, then try & quieten it ??

makes no sense to me :(

SEAN-NZ
17-02-2012, 08:37 AM
could you get some kind of paint that will take the heat? just to seal between the exhaust and exhaust wrap? then you only have to worry about rotting

wintertidenz
17-02-2012, 08:57 AM
Even with the standard exhaust you still get a louder noise at 2500-2800 RPM.

There's no way around it - it's part of the engine characteristics. Best thing to do is to replace where the cat is with another muffler.

Davezj
17-02-2012, 10:17 AM
Err??

If you want a quiet car.... why buy a loud one, make it louder, then try & quieten it ??

makes no sense to me :(

Car was like this when I bought it, it was the only thing that put me off it. I don't want to get rid of it, as it was very expensive when it was put on the car. I would have buy a complete new exhaust system to replace it, and I don't have that sort of money kicking about as loos change at the moment.

Davezj
17-02-2012, 10:19 AM
Even with the standard exhaust you still get a louder noise at 2500-2800 RPM.

There's no way around it - it's part of the engine characteristics. Best thing to do is to replace where the cat is with another muffler.

I would have put an extra silencer in the system if he cat was removable.
But it is a one piece bespoke exhaust which includes down pipes to back box. It was built one this car for this car.

VR457
17-02-2012, 06:24 PM
Can you put an inline resonator?

Davezj
17-02-2012, 06:42 PM
Err??

If you want a quiet car.... why buy a loud one, make it louder, then try & quieten it ??

makes no sense to me :(

Now when I read this again I have to agree.

When you say it like that, you are perfectly right.
It is like complaining I don't get very good mpg "Get a polo blue motion"

wintertidenz
17-02-2012, 11:03 PM
Dave - I have the same problem, my RPS system was built up with no cat in mind so it's all one piece from downpipes back.
I'm going to have to cut in to install a muffler - but the cat location is unfortunately the best for it, as it accommodates a larger muffler than elsewhere.

One of these basically http://www.trademe.co.nz/motors/car-parts-accessories/performance/exhaust/auction-448366083.htm

Nick Mann
18-02-2012, 01:18 PM
The bung in the tail pipe makes a big difference to power, but a massive difference to noise. I guess it depends if you want to have to remove it to open the car up? They are eay to remove, often just one screw, but still too much to do whilst sat at the traffic lights. I have no idea on the wrap.

wintertidenz
18-02-2012, 01:24 PM
One of these would also do it.

http://www.redlineperformance.co.nz/?action=products&part=26348

Nick Mann
18-02-2012, 03:25 PM
Yep, that'd work.

I also remember Turbo Steve talking about a similar thing that was set up to the boost pipework and set to work in a similar way to the wastegate - when the pipework sees pressure the actuator opens a flap in the muffler. I think he was talking about making one rather than buying one though....

wintertidenz
18-02-2012, 11:41 PM
What about a twin loop muffler? You normally see them on Hondas, but they should work just as well on our cars.

EdmundVR4
23-02-2012, 12:48 AM
This works on my 115mm muffler tip.
http://apexi-usa.com/shop/index.php/silencer-for-gt-spec-and-n1-turbo-active-tail-silencer.html

Wodjno
23-02-2012, 12:51 AM
What about a twin loop muffler? You normally see them on Hondas, but they should work just as well on our cars.

Sure they would be 2 restrictive for a Turbo application ?

wintertidenz
23-02-2012, 10:33 AM
They do make 2.5 and 3" applications... the main theory is that when you put your foot down, all gases go out the muffler instead of partly passing through the loop... so full throttle shouldn't hurt performance much.

Davezj
23-02-2012, 09:37 PM
i see what mean and if you look closely you can see the spring in the restictor section that i presume opens up the rest of the tail pipe when the exhaust pressure increases to the required level to over come the spring rate of the spring.