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Exhaust Noise
Jeano - 29/7/15 at 11:40 AM

I have a ZX12 and it pritty loud, im concerned with trackdays tbh.

My end of my exhaust is bolted on so i can fit a wadding to reduce noise. Is the below the best kind of product to use?

Also are they reusable if i remove and then want to refit.

http://furoreproducts.co.uk/exhaust-parts/151-accoustafil-type-exhaust-packing-sheet-500mm-x-400mm.html

adithorp - 29/7/15 at 12:53 PM

That or acoustafil. It's sewn compressed with a low melting point thread, that once you run the car, melts and allows the mat to expand to fill the silencer. You would struggle to get it out undamaged and reuse it after. You need to do a search on how much to use as the amount recommended for accoustafil has been found to be too much by many.

[Edited on 29/7/15 by adithorp]

Davey D - 29/7/15 at 01:43 PM

How big is the exhaust youve got fitted? if you have a small silencer then it will be harder to drop the noise right down

Jeano - 30/7/15 at 08:54 AM



Haven't measured the diameter yet

AdamR20 - 30/7/15 at 09:14 AM

Hmm, yes, that is a tiny can.

Have used Acoustafil myself before and it does what it says on the tin (providing you use it sparingly, as has been said), but not sure how effective it'd be in your case. Worth a try for the money!?

adithorp - 30/7/15 at 09:34 AM

That looks like a comined cat'/silencer so the heat effected bit is where the cat' is and the back bit is the silencer. It would appear to be a 5" dia' with a fairly large bore; maybe 2.5"?
For good silencing you want as long as possible and as large a cross section of silencer (between the perferated tube and outer cat dia'. Overall yours probably isn't ideal for either

You might as well try the re-pack (it might have nothing in there) but I suspect you might have to eventually fit a bigger box.

Slimy38 - 30/7/15 at 11:02 AM

Can you do something with baffles rather than packing? I appreciate that it might kill a few horses at the wheels.

Jeano - 25/2/16 at 11:34 AM

I measured my exhaust outlet today at 2.5mm.

Im yet to remove the tip to see whether i have wadding inside to repair but am thinking of ordering the below in addition to the wadding in order to keep it down.

3" Universal Exhaust Silencer Db Killer Fits Jap Box Baffle Bung

Jeano - 1/3/16 at 12:34 PM

Tested at 117dB within 0.5m of exhaust at 45 degree etc at 7500rpm

only 99dB from 2m on the other side of the car thou

concerned if i will get it bought down but i have ordered wadding and a bung

Oddified - 1/3/16 at 02:40 PM

quote:
Originally posted by Jeano
Tested at 117dB within 0.5m of exhaust at 45 degree etc at 7500rpm


That's loud, you'll be very lucky to be able to play on any track with it that loud. I'm surprised that pc plod hasn't shown an interest too!.

As mentioned above, you'll probably have to change the silencer to a larger outer diameter (longer and/or greater diameter = quieter). Try the wadding/bung but there probably just isn't enough depth of wadding around the perferated tube and outside case to absorb the noise/pulses enough.

Ian

Jeano - 3/3/16 at 08:21 AM

Ordered some wadding, plan at weekend is to remove the removable baffle and check there is wadding and then repack it or put some in!

Then install the bung i have purchased and review it once more. Ill put new batteries in dB meter to check its accurate.

Phil_1471 - 3/3/16 at 02:40 PM

Where did you get your db meter from? Worried about mine massively now, seems like quiet a few are having issues with noise on track days... Sigh!

The Black Flash - 4/3/16 at 01:06 PM

quote:
Originally posted by Phil_1471
Where did you get your db meter from? Worried about mine massively now, seems like quiet a few are having issues with noise on track days... Sigh!


The 10 quid jobs from ebay are pretty good IME.

Jeano - 4/3/16 at 02:14 PM

Agreed, got mine from Amazon

http://www.amazon.co.uk/Digital-30-130-Monitor-Decibel-Pressure/dp/B00ERQC7Y0/ref=sr_1_1?ie=UTF8&qid=1457100866&sr=8-1&keywords=dB+meter

Phil_1471 - 4/3/16 at 03:14 PM

All these £10ers are adding up lol, how accurate is the iPhone app compared to your meter?

Jeano - 4/3/16 at 05:56 PM

Everyone says acustafil needs less than recommended. How much less? 1/2? 3/4?

The Black Flash - 4/3/16 at 09:00 PM

quote:
Originally posted by Phil_1471
All these £10ers are adding up lol, how accurate is the iPhone app compared to your meter?


I don't know for sure, but as I understand it, the microphones in phones do not respond well at the ~100db level - i.e., not very well I don't think.
But I've not tested.

907 - 5/3/16 at 12:12 AM

I have two iPhone apps, and a £50 db meter.


All three are within 1 db of each other in the 80 to 120 range.

Phil_1471 - 5/3/16 at 07:13 AM

Nice to know, will use my iPhone app to get a rough idea :-) save some cash

The Black Flash - 6/3/16 at 04:55 PM

quote:
Originally posted by 907
I have two iPhone apps, and a £50 db meter.


All three are within 1 db of each other in the 80 to 120 range.


Good to know. I stand corrected

Jeano - 6/3/16 at 06:08 PM

so dismantled my exhaust at the weekend, just to find that there was bairly an filling material to the baffles, just one thin piece around the outside that kind of floated around the baffles,

i took the entire exhaust off so i can get the hole drilled in for my new bung so will repack the exhaust and see what she measures.



barely any fluff


Davey D - 6/3/16 at 08:47 PM

That exhaust wadding looks quite dense and compacted? If it is then that won't be helping with the noise

Jeano - 7/3/16 at 06:52 PM

Very Dense, very compacted and one thin layer around the entire exhaust around 2mm.

Acoustafil, what does everyone recommend in rtio to there recommendation 80% or shall i just go with it to maximise reduction

Phil_1471 - 8/3/16 at 08:26 AM

Just had my acustafil delivered, be interesting to see how you worked out how much and what the sound is like etc, let us know?!
At idle, my car is 68db's not looking good for a track for me unless I put on an exhaust the size of a cannon.

Davey D - 8/3/16 at 10:06 AM

With my RaceCo exhaust it is filled with chopped strand loose fibreglass. They are filled to the correct amount by weighing the exhaust with the wadding inside.