Repackable silencers - is there a permanent filling?

[Rusti Evo]

Not only is it a bore repacking the silencers after every outing, but there is always a risk of breaching the drive-by meters as the packing blows out through the event.

I was assuming the bigger teams have put some effort into finding a stuffing material that stays put. My experiments with a variety of materials have all been dissapointing.

Anybody come across a permanent fix?

Car is a mid engined V8.

[Shelsleyf2]

Hi, First are you doing it correctly?. You should start by winding stainless steel wool around the perferated tube and then filling the rest with the sound absorber. You have a choice of material for the absorber, Rock wool, Basalt fibres and I believe now you can buy continous fibre. The continous fibre is as the name suggests very long strands, the long strand stuff is supposed to be the best and last longest, it has to be wound round the perferated tube carefully so as to not break. By the way too much packing makes the exhaust louder since the sound waves are bounced straight back into the pipe. Some blow out is almost inevitable...All this was told to me by a well known exhaust manufacturer.

Hope it helps Jimmy

[Scuffers]

Acousta-fil is really good stuff, although it's not cheap.

[Mazda Baiter]

As Shelsleyf2 said, alot of the performance is down to the technique used to pack it. We used to pack silencers for corporate car doing 4 hrs running a dy 6 days a week 10 months of the year. Due to the way we packed the silencers they didn't "blow out" or start to fail. they lasted the full 10 months.

We used to use wire wool, held on with lockwire to stop it shifting. Then a loose fibre material, ie, not a woven fibre. Then last of all a woven blanket type of matting. There should be enough of the second layer to make the third layer fit tightly in the silencer. It should be packed tightly enough not to rattle when you shake it after re-assembling but not too tight so that it will just bounce the sound back into the exhaust. Common sense should see you alright with judging this.

[cmsapms]

What thickness of wire wool should be used - ie how deep a layer?
What grade of wire wool do you recommend?
Where's the best place to get the ingredients?

Thanks chaps

[Mazda Baiter]

cmsapms said:

What thickness of wire wool should be used - ie how deep a layer?
What grade of wire wool do you recommend?
Where's the best place to get the ingredients?

Thanks chaps

Not sure. I just used to go to stores and get the stuff from them. Sorry I can't be more help.

[F355GTS]

You need to use long strand e-glass, I do around 20 to 25 trackdays a Year and in 3 Years haven't needed to top it up

[anonymous-user]

You are going to ideally want to use inconel wool on that car, being a mid engined V8 there isnt much loss in temperature before the silencer, which will melt the packing and kill stainless steel wool.

Speak to Leon at Alunox in Wrexham, he can sort you out with a set of silencers custom made for the job that will work and last.

[456lbft]

Shameless plug time. We stock the stainless wire wool that is specifically designed for silencers, and continuous fibre e-glass or s-glass (much more expensive but essential for turbo or rotary engines) Most of what has been advised in this thread is valid. We have worked out that an optimum density for the packing should be 150grams per litre of silencer volume. There are of course lots of variations possible depending on the exact application. See my profile for our website details.

[Rusti Evo]

Thanks for the thoughts guys. The problem with my car is the same as the Stealth and Mosler - the silencer is right on the end of the merge collector and consequently trashes convensional packings double quick. Inconel wool - now thats a good idea!

[anonymous-user]

It's actually a bit more complicated than just the inconel wool, you start the packing by using a woven sock of inconel that goes around the perf tube, then wrap that over in the wool, then pack over that with the high grade packing material. I've tried the stuff mentioned above for rotaries, it doesnt work in this application, the heat source is too near the material even for that stuff.

I've just been running a McLaren 550BHP mid engined CanAm car with the inconel setup for 7 races down in NZ, it worked without any issues. Leon is very good and does a lovely job, so give him a call, tell him i sent you.

[Scuffers]

Rusti Evo said:

Thanks for the thoughts guys. The problem with my car is the same as the Stealth and Mosler - the silencer is right on the end of the merge collector and consequently trashes convensional packings double quick. Inconel wool - now thats a good idea!

I run a ProSport, same setup, I use Acousta-fil , never had to change it since (including the Britcar 24H weekend).

I did try the wire-wool lining with E-glass but that lasted ~2 hours tops, the Acousta-fil seems to be fit and forget.

Use it on my Honda cars to, and even with EGT's over 900C it's doing OK.