upgraded exhausts that are not too loud and gain more power?

Discussion in 'Performance Mods' started by joshua97, Dec 10, 2012.

  1. joshua97

    joshua97 Member

    hi i run my 66cc with out baffles in the exhaust and hit up to 51 kph or 37 with baffles lol ,does anyone know of an exhaust system thats cheap and has a good power increase? (other than expansion chamber) , cheers :)
     

  2. jaguar

    jaguar Well-Known Member

    For a power increase you have to modify the standard exhaust. click onto my signature link.
     
  3. Fabian

    Fabian Well-Known Member

    2.5 feet of flexible high temperature silicone hose will dramatically quieten exhaust noise
     
  4. joshua97

    joshua97 Member

    thanks, i tried it and its awesome cheers :D
     
  5. Nate888

    Nate888 Member

    you can put layers of any type of insulating material that's relatively heat resistant around the expansion chamber and put a silencer muffler after the expansion chamber to give best of both worlds, power and noise abatement
     
  6. jaguar

    jaguar Well-Known Member

    I bought a db noise meter and know for a fact that a normal expansion chamber and a normal silencer is way too loud for anywhere other than the motocross track.
    That's why I researched the belly stinger and other forms of silencing so people can have the power without the noise.
    I have a new design of silencer that I've been testing on my Suzuki and it is free flowing and very quiet, a real breakthrough. But until I make construction plans available you can still use my other design that is on my site.
    Using the belly stinger and my stealth silencer is good but still on the edge of just barely being acceptable for street use. I can't imagine using anything less.
     
  7. Nature girl

    Nature girl New Member

    Some sound advise there. I have to share my mix and match of exhaust parts. Copper plumbing pipe, a homemade silencer that a friend built, regular banana pipe, and some stock brackets from chain tensioners.
    Works great, not too loud for my area.
     

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  8. Nate888

    Nate888 Member

    I haven't tried it, but jaguar's design looks legit.

    i believe you about normal expansion chambers being too loud. my own data come from a kludged together pseudo expansion chamber solution i put together in a rush to get my ride working. it consists of the 'skeleton,' which i mad by crafting a primitive expansion chamber out of steel cans (there's a post about it in my history) bent into shape, with a minimal silencer part at the end - top 1/3 of 23oz aluminum can with half a steel scrubber stuffed in and tacked on place. it didn't seal, not even close like that, so I built it up using layers of aluminum foil and cold weld exhaust&muffler repair putty. after enough of this heat shielding, I cheated and used Bondo, plus more foil. all this material seemed sufficient heat shielding, but it seemed maybe a little bit brittle and was still pretty loud, but already several dB better than straight pipe or expansion chamber alone. so I added couple layers of furnace tape and duct tape, and actually I put more Bondo, stretched part of a broken inner tube over the whole thing, added one more layer of Bondo and foil, put some more tape and painted it. it's pretty dang quiet now and feels pretty solid and stable.

    I was a little uneasy about the safety and integrity of using rubber in there like that, so I can't recommend it at this point, though it's worked well for me for the past four or five hundred miles (trips up to 15 or 20 min, WOT for maybe 15-20% of that, probably 4 or 5 min at the longest stretch)

    Jaguar points it out on his site that an expansion chamber tends to be loud because the walls of it will flex from the pressure and reverberate like a drum or loudspeaker, sending out intense noise that bypasses the silencer completely. that's 100% right. what I'm saying is that layers of heat and acoustic shielding can be wrapped around the pipe and chamber to cut down this sound too. it's even easier than making a silencer muffler, though I'd urge you to make yours hopefully a bit more professionally than how I made mine though... ;)
     
    Last edited: Nov 6, 2016
  9. butre

    butre Well-Known Member

    my custom expansion chamber peaks at 96 db which osha says you can be exposed to for 8 hours a day without hearing damage with the only noise reducing feature being a stinger placed 6 inches into the pipe. I plan on eventually wrapping it to reduce the noise further. I may install an actual muffler eventually as well.
     
  10. jaguar

    jaguar Well-Known Member

    94 db is the noise limit for motocross !! (at 20" away at 45 degrees)
    It's very loud.
    My torque pipe with stealth silencer puts out half as much noise as a 94db setup.
     
  11. butre

    butre Well-Known Member

    I measure as an audio engineer does, not as a race track does. that's one meter from the source at 45 degrees. 20 inches or 1 meter is close enough to give similar results with maybe a 1 decibel difference.

    the overwhelming majority of the noise my bike makes is in those straight cut gears and I haven't found a good way to drop that noise by any considerable margin without adding bulk. thick grease helps, but not enough. if someone would make a set of helical gears for a china girl I'd be their first customer.

    come to think of it, I haven't measured since I built that chamber, and I've added silicone dampers between the fins and quieted down the intake quite a bit since then.
     
    Last edited: Nov 7, 2016
  12. jaguar

    jaguar Well-Known Member

    If yours is 96db at 44" (1 meter) distance then how much higher would it be at 20"?

    you're just proving my point.

    Did you try my fix for the gear noise?
     
  13. butre

    butre Well-Known Member

    you mean using valve grinding compound on them? I haven't tried it, but I suppose the logic is sound. still it weirds me out to put abrasive material in gears on purpose.

    doesn't help that I have a bent crank from the time my bike ate my pants either. doesn't make too much extra noise under load, but it's not easy to measure sound pressure under load
     
  14. jaguar

    jaguar Well-Known Member

    You would be modifying the design of the gears, no different than modifying the engine.
     
  15. skyash

    skyash Active Member

    Its called back lash when the gears are to close together not enough room for untrue spin you can have a big gap between the gears if it doesn't slip or maybe the gears are over sized ...but apart from taking them off and grinding each tooth one by one and probably unevenly. the compound is the best option and should get an evon finish .or keep riding and Ware it in .
     
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