progers
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| posted on 13/3/06 at 09:46 AM |
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The short answer is that you can't make the MNR quieter as it is limited by its size (unless you start playing around with internal baffles that
can play havoc with power if not carefully done).
For a straight through can the only way you can make it quieter is by increasing the size. As mentioned above you'll need at least 6"
width and as long as you can make it. You can use stainless end caps but using an ally shroud is usually quieter. Guys I've known with
busa's have often had to resort to 7" x 30" cans to get the noise down enough. Are you running an airbox? That will certainly help
reduce noise as induction noise is a big contributor too. I've also found that wadding in cans often needs replacing/topping up to keep the can
quiet, if you have been running a rich mixture is can cause some interesting scorching inside the can :-)
I just managed to squeak past the Donington 98dB driveby limit with a big can and keeping the air filter under the standard MK bonnet (no air
scoop).
Most of the tracks that are not critical with noise e.g Snetterton, Cadwell, Anglesey etc where 105db is the nominal limit I have never seen them use
a noise meter. Its only the Donigton, Castle combe where they will actively test.
- Paul
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smart51
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| posted on 13/3/06 at 12:12 PM |
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How much is a larger silencer going to cost me then. I could pick up an R1 can off eBay but if a larger straight through can will give me the same
noise reduction with less power loss then this seems to be the way to go.
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MrSandMan
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| posted on 14/3/06 at 11:47 PM |
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quote:
usually the minimum required for trackday use is 28'' long by 6'' dia and ally will always be quieter than
stainless.
So how does Carbon Fibre compare to ally and Stainless. I have gained one from eBay and am hoping that it will be better than the old chrome box that
was showing 112db.
Too loud sir!!
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ChrisGamlin
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| posted on 15/3/06 at 12:37 PM |
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quote:
Originally posted by smart51
How much is a larger silencer going to cost me then. I could pick up an R1 can off eBay but if a larger straight through can will give me the same
noise reduction with less power loss then this seems to be the way to go.
I have just bought a 29 x 7" can from Simpson Race Exhausts (near Slough) for about £220 as part of a group buy with the WSCC. Im not sure
exactly how much discount we got but I got the impression they would usually be ~£250 which is good value considering the quality of them, much
cheaper than the SBD and Raceline ones but just as well made.
I havent picked mine up yet but it should look something like this:
 
Simpson can
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smart51
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| posted on 15/3/06 at 04:22 PM |
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I have phoned them already. They were quite expensive at £250 + VAT.
How much larger do I need to go to reduce the noise by 3dB?
Which is better, larger diameter (6" instead of 5" or larger length (upto 30£ instead of 24"?
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smart51
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| posted on 15/3/06 at 09:04 PM |
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I did a simple test today. I took a piece of 0.5mm thick aly and bent it over the rolled edge of the tail pipe on my car so that it blocked off half
oif the area. It reduced the noise by 4dB which is what I wanted. A short drive showed that it was a little less clean starting but drove normally
at full throttle upto 9000 RPM. After that it hit a bit of a wall in terms of power output. A better outcome than the R1 can that I tried, on
balance, but still not good. Perhaps a proper dB killer would be slightly better. OK in an emergency perhaps.
Under bonnet padding had no effect at all.
So I guess I need a new can. . How much bigger than 24" x 5" should I go for?
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Avoneer
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| posted on 15/3/06 at 09:49 PM |
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Smart51,
Far from up and running yet, but have a Supertrapp, Yoshi can and R1 can that will all bolt on and currently working on a homemade 6" x
40" straight through ali can to overcome all these problems.
Have you got a sound meter?
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
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smart51
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| posted on 16/3/06 at 07:52 AM |
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Yeah, I bought the one from Maplins. I guess it might not be too accurate but I expect it to be repeatable, so If I measure a 3dB change, it will be
correct, even if both readings are 2 dB out.
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smart51
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| posted on 30/3/06 at 09:53 PM |
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My new silencer from the kit car workshop arrived today. The 750mm can was actually only 660mm. Had words with Martin from TKCW who said try it
anyway and see how it is. It is a whole 5dB quieter than my old can at 102dB. I am now legal for track days.
Marc from MNR measured my exhaust noise at Total Kit Car Live last week at 101dB so perhaps I didn't need a new can afterall. I have been
taking my measurements with the meter on max hold mode and he just read the screen. Maybe that means my new can would get me in at donnington.
I'm still not happy with TKCW though. They supplied the silencer with a tailpipe that extended so low that it would have touched the floor,
despite me telling them not to. I have cut it off but am not happy with a sawn edge. Is there any way I can trim a tail pipe that wont melt / fall
off / look like a tarted up saxo?
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marc n
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| posted on 3/4/06 at 08:05 AM |
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colinn i have some preformed rolled edge tubes the will fit over the 2 inch outlet that you can tack / ivet on if thats any good ????
best regards
marc
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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procomp
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| posted on 3/4/06 at 09:43 AM |
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Hi colin if you need any bits welding stainless or ali just pop in . bet you cant wait to get it on track can you.
cheers matt
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