Repacked my can with acustafil two years ago, it definatly sounded quieter and I didn't have too many noise problems though towards the end of last year noise raised its head at Oulton park, managed to get through test but don't really want these problems to continue.

Fast forward to today, whipped the can off pulled it apart expecting to find the acustafil to have degenerated, to my horror it looks aside from been black pretty much as it did when I put it in.

It does seam a little dense around the baffle tube some places a little hard and brittle, but it also looks like I may have over packed it, (to the eye at least) I did use their online calculator and put in the recommended amount there calculator gave which pretty much filled the can prior to first start when the bands melt and it expands, it hasn't really expanded to be honest.

What's anyone's thoughts/opinions guess you can over pack ?

The working length of the can is 22", 6" diameter with a 2" perforated pipe through the middle, shouldn't be having noise problems ?

What are you guys using and what levels are you been tested at ?

Hayabusa engine.

with a can pretty much the same size as yours on my R1 motor and acoustafil i never have any issues as long as i do 105db days, which i'm guessing your oulton day was.

didn't use anything like the recommended amount by there calculator. cant remember how much i used but i don't think it was much more than 2/3rds full when i packed it.

The calculator is utter rubbish. I bought the amount it said, and it as more than twice the amount I ended up using!

So do we think I over packed it making it a solid tube ?

Just to add confusion, a resonance chamber ?

I'll try in words, it as been suggested as the can is long enough to take it I make a small chamber at the front with no packing at all, to do this I weld a disc onto the inner baffle tube so it sits say 4" from the front of the silencer when it pushed in, pack the rest as normal, this hollow chamber in theory will act as a resonance chamber and further disturb/quieten sound waves.

Make any sense, thoughts ?

I don't know about having the chamber empty, but I have read that a baffle 1/3rd the way along reduces the noise. What I read said put wadding both sides.

I've also heard several times that the quantity calculator results in over packing.

It sounded very "tinny" at Oulton and I expected you to find an empty box.

I think your al right, I over packed and was running pretty much just a unsilenced straight through pipe.

The standard R1 can features a full diameter empty chamber as its first element.

there was a formula on here a long time ago for the resonance chamber. if i recall correctly ideally it needs to have the perforated bit removed as well. you need something like the uncompressed volume of one cylinder timesed by the resonate frequency by the pipe diameter. I'm sure it ends up being quite large.

OK, I've ordered 1mtr 500 wide, calculator says 1.89 mts, I'm going to put that in which will leave about 70mm totaly empty, make a big polo blanking plate tack it to inner perforated tube 500 along and see what happens, pheasable? Should I cut the last 70mm of perforated tube off or leave it, maybe make holes bigger?

The chamber in the R1 can is empty. No perf tube through the centre.

Just put 1 meter in can, does it look like enough, will it expand to fill the can ?

Back in the day Jon, I think I overfilled mine too - made sod all difference

quote:

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Originally posted by yellowcab
being honest I wasn't sure how much to put in, but I did the calculator thing on their website, so I just put in the amount they stated...

here are some pics of the process for those that can tell me I've done it wrong lol


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so what do people think, doesn't look enough to me though google finds comments where people have 1/2 filled the void and got results ?

i cant remember that well but i think that is something similar to how mine was.

The 'chambers' used on some silencer designs are actually Helmholtz resonators. They only attenuate a narrow band of frequencies unlike the more broadband attenuation of an absorption silencer and several of them are normally used together to attenuate a wider range of frequencies.

The resonant frequency of the chamber is determined by it's dimensions, so just adding a random sized chamber is unlikely to do anything useful. I would just fill it with wadding.

Hmm, so looks like it's a "cunning ploy" for them to sell more and make more profit - pretty shabby really!

Jon, when you used a metre in your can (which sounds nominally the same size as mine) did it expand sufficiently?

Cheers,


Simon

Hi,

yes it did, think it measured something like 101, 102 static once settled, it just looks wrong when you put it in.