Quote:
Originally Posted by cRiPpLe_rOoStEr
Getting an exhaust pipe with less than 1kg doesn't seem so easy at all, but it also doesn't seem impossible. For soundproofing and some modest degree of thermal insulation you can use the same glass wool used to insulate refrigerators and ovens.
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Rock wool has even better sound insulating abilities from my experience, might be bit heavier, but difference is perhaps not too much.
For me low level of sound is one aspect of low environmental impact of transportation, so I have modified my scooter exhaust to be a lot more quieter than original and also it seem to flow better than original, weight is bit more though, but better flow reduced fuel consumption more than weight increase increased so in total fuel consumption was reduced while power was increased.
Cost was next to nothing, little bit of electricity, rock wool I had around because of house renovation, little bit of time.
I used metal wire net to be 'pipe' for exhaust inside the silencer, then around that I packed rock wool, because I wanted maximum silencing I did pack it loosely, I could of packed it tight when it would of been better flowing, also using less holes would improved flow even more, but that was not my primary goal.
Old exhaust pipe was big empty can and at the end of it there was tiny silencer, I filled silencer and big empty can with rock wool, had to of course cut that big can open.
In 2-stroke that would of not been possible, because exhaust is important to be just right, but for 4-stroke exhaust is not so important as long as there is not too much of resistance.
Similar level of sound reduction would cost over 80 for good quality silent silencer, so I think it was worth it.