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quieter exhaust


custom-vince
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im still looking at ways to reduce engine noise. wrapping expansion chamber, extending muffler...

The TOP80 and Nirvana Exhaust that gets fitted to their Simonini. Neither of which resemble the scooter style expansion chamber, and tubular muffler that is common. BUT both of those engine sound sweeter (lower tone) and their exhaust systems are lighter weight.

How does it work without the tuned shape of an expansion chamber to give the correct back pressure?

What is in them? any silencer wadding, divider baffles

Why is that style not used on other machines? polini, vitorazzi, h&e, cisco, corsair, sky-engines, fly engines, technofly, simonini, etc

top80 exhaust

pg00349-t1.jpg

Nirvana Simonini

pg00703-t1.jpg

I was never fully into scooters or 2 stroke bikes. I had an RG500 but that has 4 tiny pipes and made a huge load of noise which was fun at the time.

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Is that it, it still has and needs the cone shape to reverberate the pulse wave back towards the combustion chamber to crest the nessersary back pressure. A simple square ended tube can't do that?

I read adding 5" to the muffler can reduce noise by a further 5db

Wrapping the expansion chamber again reduces noise.

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I guess the shape of the cone reflects the range of the 'powerband'.

The cone reflects the pressure wave progressively so the pulse returns to the exhaust port at the correct time to keep the fuel mix in the head.

A shallow cone would give a wider but weaker powerband.

A steep/flat cone would give a very good return pulse, but because it is so narrow it will only work for a small rpm range.

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Is that it, it still has and needs the cone shape to reverberate the pulse wave back towards the combustion chamber to crest the nessersary back pressure. A simple square ended tube can't do that?

I read adding 5" to the muffler can reduce noise by a further 5db

Wrapping the expansion chamber again reduces noise.

Vince, There are cones inside just not in the conventional way. If you cut one open you will understand.

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