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Exhaust Components

bmetcalf

Well Known and Active Forum Website User
VOC Member
The collector is the Y junction for the two pipes and you could use it for the exhaust on a special. The reverse cones probably wouldn't offer much for a Vin, although Davidd mentioned a full megga on a Flash, I think. The Sports Motorcycles Hailwood bike in BOTT at Daytona in '83 or so had two different reverse tips, one for sound testing and one for racing. :cool:

The spring kits and clamps seemed more useful than the reverse cones.

Can collectors be used on a Vin twin and what are the advantages?
What are the advantages of a reverse cone compared to a "standard" silencer on a Vin twin?
 

vibrac

Well Known and Active Forum Website User
VOC Member
Yes 105Db is a hard act to follow with performance on the track
but I suppose you fast road guys wont worry about that
 

davidd

Well Known and Active Forum Website User
VOC Member
Bruce,

The megaphone has always seemed to produce more power than the straight pipe for Coburn Benson specifically. He rarely raced without it and it was on the bike at Daytona when it qualified 114 mph. On my bike I am currently fitting a megaphone but I have not tested it on the dyno. I was getting 42 bhp with the straight pipe. Carleton picked up power by using a megaphone on his Flash and ended up at 43.5 bhp. But, I have to agree with Tim, the sound standing behind it would make your teeth hurt. He would not be allowed to run it with today's rules.

David
 

vibrac

Well Known and Active Forum Website User
VOC Member
UK noise test is done at each meeting plus random.
There was a way round the test. Once when the Comet stopped running at a meeting,I volunteered to be a noise inspector (Poacher turned gamekeeper?) up came an NSU max as noisy as a rambler shouting at trail riders but as the engine got to the testing rev range it went quiet he showed me a cross blind pipe at right angles to the main pipe under the engine he had the length tuned to silence the engine at the magic revs (look up Helmholtz chamber) another low side car failed until we put a brick under the back wheel then it just passed.
all gone now because they also do flyby noise testing at track days
 

BigEd

Well Known and Active Forum Website User
VOC Member
VOC Forum Website Moderator
Way back when I was AC-U noise meter operator at Vintage meetings we often called riders randomly down to the scrutineering area for a noise test. Roger Moss with his very rapid Scott two-stroke twin always passed easily. At one Oulton Park meeting Roger's number came out of the hat and I decided to go and find Roger and do the test where he was parked in the paddock. I watched Roger fire up the Scott and did the test. The noise from the short stub pipes traditionally run by Scott racers sent the meter way off the scale! (This at a time when the limit, I think, was 115 Db.) Roger being the gentleman that he is just said OK and put the bike back on his trailer.
How had it managed to pass the noise test before? Years later Roger told me the secret. When he was called down for a noise test he always pushed it to the test area with the engine already running having already started it in the paddock by pushing it in reverse. The two-stroke was quite happy to run backwards and ran much more quietly when doing so.
Roger had the last laugh as this episode lead him to fit an expansion chamber exhaust system that was not only quieter but made the Scott even more rapid!:)
UK noise test is done at each meeting plus random.
There was a way round the test. Once when the Comet stopped running at a meeting, I volunteered to be a noise inspector (Poacher turned gamekeeper?) up came an NSU max as noisy as a rambler shouting at trail riders but as the engine got to the testing rev range it went quiet he showed me a cross blind pipe at right angles to the main pipe under the engine he had the length tuned to silence the engine at the magic revs (look up Helmholtz chamber) another low side car failed until we put a brick under the back wheel then it just passed.
all gone now because they also do flyby noise testing at track days
 
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