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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Silencer for Series C Comet
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<blockquote data-quote="vibrac" data-source="post: 32623" data-attributes="member: 60"><p>Its been said earlier in the thread you will never get effective silencing with a body diameter of the standard unit you need at least 4” diameter and not only is that ugly but it has to be mounted at a higher level.</p><p>But it sure works with no baffles and a straight through 2” pipe I get 100db from a absorbs ion silencer on the Comet and if I had an annular exit of same X section area I guess I would be down in the low 90’s</p><p>Not much comfort to a standard guy but worth considering on an Egli</p><p>Incidentally the ACU noise test is run at a certain rev range dependant on stroke I was a sound scrutineer at a meeting some years ago and a NSU Sportmax came to be tested boy it made a racket! But when we tested it just at the measuring speed it went some 10-15Db quieter and passed</p><p>He showed me the trick under the engine he has a cross pipe at right angles with a blind end he had set the bike up at the measuring revs and slid this cross tube like a trombone till it went quiet then brazed it up.</p><p>It’s called the Helmholtz effect (I think) perhaps that’s the answer set it to 4200 on a Comet and see……</p></blockquote><p></p>
[QUOTE="vibrac, post: 32623, member: 60"] Its been said earlier in the thread you will never get effective silencing with a body diameter of the standard unit you need at least 4” diameter and not only is that ugly but it has to be mounted at a higher level. But it sure works with no baffles and a straight through 2” pipe I get 100db from a absorbs ion silencer on the Comet and if I had an annular exit of same X section area I guess I would be down in the low 90’s Not much comfort to a standard guy but worth considering on an Egli Incidentally the ACU noise test is run at a certain rev range dependant on stroke I was a sound scrutineer at a meeting some years ago and a NSU Sportmax came to be tested boy it made a racket! But when we tested it just at the measuring speed it went some 10-15Db quieter and passed He showed me the trick under the engine he has a cross pipe at right angles with a blind end he had set the bike up at the measuring revs and slid this cross tube like a trombone till it went quiet then brazed it up. It’s called the Helmholtz effect (I think) perhaps that’s the answer set it to 4200 on a Comet and see…… [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Silencer for Series C Comet
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