Simon
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| posted on 5/1/04 at 10:18 AM |
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Exhaust Wadding
Peeps,
Bought some exhaust wadding from DT, which comes on a roll.
Is the idea that I break this up and put into can, or roll it around the perforated tube.
Any suggestions appreciated.
ATB
Simon
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VinceGledhill
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| posted on 5/1/04 at 03:10 PM |
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As far as I know you put the inner perforated tube inside your outer tube then pack it in all round until you can pack it in no more.
That's how friends of mine have done it. PS where did you buy it from. That's my next job.
Regards
Vince Gledhill
Time Served Auto Electrician
Lucas Leeds 1979-1983
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Simon
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| posted on 8/1/04 at 10:45 PM |
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Vince,
I got the packing/perforated tube from Demon Tweets - IIRC £11.62 + vat/del (for packing)/£14.19 + vat/del per metre Each pack of wadding alledgedly
enough for a 2 litre can - hence the reason I asked whether it should be broken up. My can's each amount to about 1.2l volume and there
doesn't appear to be anywhere enough
A point of interest re cans - I tried ordering a metre of 5" diameter tube from DT - for £34.76 + deivery and VAT. They didn't have any,
so ordered same from Custom Chrome. £30.00 delivered - so quite chuffed.
ATB
Simon
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craig1410
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| posted on 7/3/04 at 01:54 PM |
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Simon,
I've been doing some calculations on how much wadding I'd need for my silencers which I'm planning to make soon and it comes to 8.5
litres in total (5" casing with 2" perf tube and 800mm long each side). This would require almost £100 quids worth of wadding which seems
totally insane!! What exactly is this wadding? Is it just long strand fibreglass matting and if so, can't it be bought much more cheaply from
the likes of a marine chandlers?
I worked out the costs of making a pair of silencers and it came out at about £150 for the parts alone. At that price I'm better off buying a
pair!
Have I missed something?
Cheers,
Craig.
ps. Have you got a new email address yet?
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Peteff
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| posted on 7/3/04 at 03:03 PM |
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Have a look on here.
http://www.milnerconv.co.uk/Pipe.htm
They aren't far from me and have some useful looking stuff. You can use rockwool for stuffing silencers along with stainless wire wool round the
perforated tube.
yours, Pete.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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craig1410
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| posted on 7/3/04 at 04:59 PM |
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Thanks Peteff,
They look like quite a useful source of bits for exhaust bulding. It was mild steel that I was plannign on using to be honest but I might be tempted
to use stainless and just tack weld everything in place with my Mig and get it done fully by someone with a Tig.
Cheers,
Craig.
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stephen_gusterson
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| posted on 7/3/04 at 10:42 PM |
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if you are using mild steel, why not just buy summat ready made from a road car?
I used the rear box from the 85-89 approx 2.4/2.9 ford granada.
its a strait thro glass pack, and I have one on each side of my v6. really quiet - even in the garage
38 quid plus vat
atb
steve
 
Rescued attachment exhaust.jpg
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flak monkey
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| posted on 7/3/04 at 10:54 PM |
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CBS do ready rolled wadding, and loose pack stuff. And its cheeper than Demon Tw*ts. Its about halfway down this page if anyone is interested;
http://www.nfauto.co.uk/cbs_products_new.htm
http://www.nfauto.co.uk/silencer_wadding.htm
Good if you have custom silencers.
Hope that helps a bit
David 
[Edited on 7/3/04 by flak monkey]
Sera
http://www.motosera.com
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craig1410
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| posted on 8/3/04 at 01:00 PM |
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Steve,
I had thought of that but was worried about not getting it quiet enough with what appears to be a fairly short silencer. Luego use a silencer of
5" diameter and about 32" length on their V8. From your photo it appears that your silencer is either very fat or quite short. Can you
confirm the dims please?
Cheers,
Craig.
ps. David, thanks for the links to nfauto's
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stephen_gusterson
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| posted on 8/3/04 at 02:09 PM |
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will try and do that for you when Im home later
but to scale the piccy, its got 50mm in and out, so that may help.
Its not particularly short or fat.
I dont know completly about exhaust dynamics, and wether speed of exhaust flow vs length is important in noise suppression, but I have 1200cc of
engine on each of em and its realy very quiet - even in a garage - sounds quite deep and no louder than a normal road car.
wether this stays true for a 2 litre or wahtever, i donno. But then, dont people use exhaust cans from 1100cc bikes on pintos?
atb
steve
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Dave Ashurst
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| posted on 8/3/04 at 08:29 PM |
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Guys
For what it's worth I get my silencer wadding locally (to me) from Tech-Craft in Warwick. No idea how it compares....
A sackful of basalt wool over the counter there is about £20 to £25 and in my case does at least two complete refills. I've got a lolocost
silencer but sorry I don't know the volume.
Basalt wool is the right stuff. It's quite heavy and gives good acoustic damping. Same as any wadding you need to pack it well and leave no
voids or it will break up too quick.
Rockwool was simply a waste of time in my experience, and won't take the heat. Peteff, clearly I should have tried your s/s wool idea.
They do some other stuffing not sure what it's called, it's white (basalt is dark brown). They say it's more lightweight and longer
lasting than basalt but louder i.e. it will tolerate more thermal abuse or running out of tune; lean, rich, advanced or retarded or whatever, but
you'll need a bigger can to get the same silencing effect.
I can't remember the phone no offhand (i.e. without getting off my backside) but they can be found in www.yell.co.uk.
Check out their range of silencers if you call in! 
The owner helps run the Prescott hill climb school, and might try to persuade you to join up and have a go, esp. if you turn up in your locost!
http://www.prescott-hillclimb-school.co.uk/
If you're coming to Warwick and fancy a pint or a cup of tea drop me a line.
regards
Dave
[Edited on 8/3/04 by Dave Ashurst]
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craig1410
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| posted on 8/3/04 at 08:38 PM |
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Steve,
Yes, I'm also at a loss to find any science to apply to this which is why I'm probably tending to overdo it rather than underdo it with
the silencer dims. My engine is a Rover V8 3.5 litre so it will be about 1750cc each side and about 100BHP each side (slightly less to start with).
I am assuming that (roughly speaking) a straight through exhaust of 2" bore each side will not present too much of a restriction to a 200BHP
motor and so my main issues are to ensure that it passes noise tests. Ideally if I could find someone who has made their own silencers and got through
SVA with them on a V8 then I'd be happy but otherwise I guess some guesstimation is required.
Does anyone know anything about the acoustic principles involved in silencer design and is there any reason why Steve's V6 would require
radically different silencers to my V8? They aren't far away in terms of power output and they are both "V" engines after all. I
suspect it's not that simple though...
Cheers,
Craig.
ps. Thanks to you too Dave on the wadding material stuff. Quite informative.
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stephen_gusterson
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| posted on 8/3/04 at 10:35 PM |
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approx 6 ins dia by 13.5 ins long
32 ins seems wildly excessive!
Most locost piccys seem to show fairly shortish boxes.....
Just to complicate things - the 2.9 granny uses just ONE of these boxes at the tail pipe. However, there are two flat expansion boxes up front, before
the exhaust merges to this one glass pack.
atb
steve
quote:
Originally posted by craig1410
Steve,
I had thought of that but was worried about not getting it quiet enough with what appears to be a fairly short silencer. Luego use a silencer of
5" diameter and about 32" length on their V8. From your photo it appears that your silencer is either very fat or quite short. Can you
confirm the dims please?
Cheers,
Craig.
ps. David, thanks for the links to nfauto's
[Edited on 8/3/04 by stephen_gusterson]
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stephen_gusterson
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| posted on 8/3/04 at 10:41 PM |
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this is a good basic primer
http://auto.howstuffworks.com/muffler.htm
used it when I was trying to figure out what to do. Somehow I guessed speed of flow vs length had summat to do with it, and thought 2.9 litres of flow
thro original exhaust had to be ok with only 1.2 litres a side, even without expansion boxes. I was right with a big safety margin.
atb
steve
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JoelP
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| posted on 9/3/04 at 01:17 PM |
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when i was doing my exhaust recently (only finised this morning...!) i was thinking of starting a thread asking for people to list their engine,
silencers and end volume to help people plan their exhausts. i ended up using the standard sierra back box, with a custom tubular manifold. hopefully
its not blowing! i had a selection of other silencing devices from the rest of the sierra system (two things) and a full polo system, but the sierra
one seemed the best fit and most likely to pass. if it fails i will just tack another unit onto the end!
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Dave Ashurst
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| posted on 9/3/04 at 07:39 PM |
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quote:
32 ins seems wildly excessive!
Most locost piccys seem to show fairly shortish boxes.....
Not sure about that, Steve.
I bet many of them are right on the dB limit (mine was) and following engine tuning after SVA I wonder how many are still legal? (no comment!). Or
how many had to restrict the exhaust even to pass the noise test?
If you want an unrestrictive system within legal noise limits then a long length absorption type box might well be the answer.
Not that you need to, Steve, evidently, but it wouldn't be difficult to call a silencer maker for advice. Techcraft (for example) seem to know
exactly what size silencer any given performance engine needs off the top of their head. Mind you they do have a vested interest..
Dave 
PS when can we hear yours BTW, young Gusterson?
[Edited on 9/3/04 by Dave Ashurst]
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stephen_gusterson
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| posted on 9/3/04 at 07:50 PM |
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if you dont mind a garage fulla crap, then a saturday in the near future becons.....perhaps one when you wont get wet or cold bringing yours over?
atb
steve
(provided its not easter week - im away then!)
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Dave Ashurst
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 posted on 9/3/04 at 09:21 PM |
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Don't you ever leave your computer?!!
Right, wet(ish) or cold no object, you're on, lets go to email and I'll see you soon
put the kettle on
Dave
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stephen_gusterson
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| posted on 9/3/04 at 10:13 PM |
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yep I do! I cant get on the pc most times in evening before 10 cos its occupied with dorks (my kids). Plus its getting a bit boring sans hippy since
he got all homophobic.
or has he found a new friend
atb
steve
ps cant find yer email address!
suggest sat 27th - wifey bday this w/e and we are pressy shopping saturday
and following w/e spent in london at an 80 year olds birthday party - thats gonna be wild!
[Edited on 9/3/04 by stephen_gusterson]
[Edited on 9/3/04 by stephen_gusterson]
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craig1410
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| posted on 9/3/04 at 10:22 PM |
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Steve,
Thanks for the dimensions, I may very well look into using the same exhaust as you, even if it is just to get things moving.
Here is the picture which gave me the idea about using a 5" x 32" silencer on each side with a 2" bore pipe.
 
Viento V8 Exhaust
I was able to scale the picture based on the 17" wheels and confirmed my estimates based on the wheelbase of the car which is specified on
Luego's website.
Cheers,
Craig.
[Edited on 9/3/2004 by craig1410]
[Edited on 9/3/2004 by craig1410]
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stephen_gusterson
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| posted on 9/3/04 at 10:32 PM |
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here is an example of a shorter one.....
if I can make out 'blade' on the site, could be a BEC
a fair few shortes on this page...
http://web.ukonline.co.uk/acwsj/photos/photos4/index.htm
atb
steve
[Edited on 9/3/04 by stephen_gusterson]
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paulf
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| posted on 9/3/04 at 10:41 PM |
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I used an MGB rear silencer for my crossflow , it fits a 50mm od pipe and is 5inch dia x 16 inches long and designed to silence a 100bhp 1800
engine.
It is not to loud on the 1600 crossflow and i think a V8 would be quieter as v8s a actually less noisy than a 4 cylinder engine as the firing order is
split between the two boxes.
Paul.
quote:
Originally posted by craig1410
Steve,
Yes, I'm also at a loss to find any science to apply to this which is why I'm probably tending to overdo it rather than underdo it with
the silencer dims. My engine is a Rover V8 3.5 litre so it will be about 1750cc each side and about 100BHP each side (slightly less to start with).
I am assuming that (roughly speaking) a straight through exhaust of 2" bore each side will not present too much of a restriction to a 200BHP
motor and so my main issues are to ensure that it passes noise tests. Does anyone know anything about the acoustic principles involved in silencer
design and is there any reason why Steve's V6 would require radically different silencers to my V8? They aren't far away in terms of power
output and they are both "V" engines after all. I suspect it's not that simple though...
Cheers,
Craig.
ps. Thanks to you too Dave on the wadding material stuff. Quite informative.
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Simon
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| posted on 9/3/04 at 10:47 PM |
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Craig,
Got some of my wadding from DT, but was expensive. Got the rest from CBS (personal visit as they are local!), though haven't opened the packet
yet, as I'm going to finish the work on the cans (trim length to 17.75" so tailpieces don't hit wheelarches - see:
http://www.locostbuilders.co.uk/photos.php?action=showphoto&photo=2Exhaust.JPG and paint etc)
The CBS (stainless) pipes are rated to about 80db (IIRC) which is about the same as my bike (standard Suzuki cans), and that (in the garage) is quite
loud. Given we can have 101db I'm optimistic it'll be ok Also, my cans have only been loosely packed as I had nowhere near enough
wadding.
HTH
ATB
Simon
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xroger
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| posted on 11/4/04 at 11:00 AM |
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Wadding
You can use fibreglass/rock wool/ordinary "pink" loft insulation wire wool ect. They all sound different!
What make a large difference to the noise is the dia/length of the system. e.g. If you had a pipe 50 feet long for your exhaust you wouldn't
need any wadding at all because the gas wouldn't have any energy left in it when it popped out the end. So the shorter/larger bore systems need
a larger dia AND longer silencer.
The best thing to do is make up some "restrictor" plates for sva and sort out a "proper" exhaust later on.
Rgds
Roger www.shinybitz.co.uk
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xroger
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| posted on 11/4/04 at 11:06 AM |
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Second note!
Sorry, some thing which I forgot to say, Is be careful when packing silencers because if you over pack them they can infact get louder!
Rgds
Rogerwww.shinybitz.co.uk
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