DIY tuned induction & exhaust, take 2

Discussion in 'Photos & Bicycle Builds' started by Nate888, Oct 14, 2016.

  1. Nate888

    Nate888 Member

    Shoutout to Steve Best for the resonant filter box idea.

    Undermeath all the Bondo & bullshit, that exhaust is pretty well tuned now too ;)

    seriously, it's almost scary fast now. most of 18-40 mph seems to be something of a power band, & I would be surprised if I'm getting less than 5-7 HP out of my motor now! 20161014_110554.jpg 20161014_110545.jpg

  2. Nate888

    Nate888 Member

    14765323127581500076685.jpg update. desert camo paint job. (hey it's a work in progress & at least I'm not afraid to experiment!)

    riding it a little more, the power band really starts to take hold at 24 mph up thru something probably in the low 40s

    also, if I cock my knee out to the side, it seems to get a better boost. you can hear the noise from the filter box change a bit & get maybe 5-8% more power. at that level I can't quite rule out that it could be an illusion, but it also seems like it might work by creating a vortex of air that helps the filterbox, or by creating a zone with either more or less turbulence
  3. Nate888

    Nate888 Member

    I tried to set up the angles in the expansion chamber to spread the Power Band, at the expense of max boost at any given rpm.

    my choice of shitty materials ensured some rough edges on its inner surface, which is the opposite of what you generally want when tuning a hi performance 2 stroke because it means more turbulence, which dilutes the reflected waves & slows the overall exhaust flow. however, I think a certain amount of turbulence helps spread the band & dampen noise, though obviously at the price of overall peak efficacy
    Last edited: Oct 15, 2016
  4. Steve Best

    Steve Best Well-Known Member

    Hey Nate, congrates for trying.
    Did you try different intake shapes?

    That exhaust wrap looks like a wasp's nest.
    Could be a stealth camo tactic with a forestland paint job!
    Nate888 likes this.
  5. jaguar

    jaguar Well-Known Member

    what kinda pipe is beneath your mud wrap?
  6. Nate888

    Nate888 Member

    the expansion chamber ends about 2" before the end of the wasp nest/elephant trunk part. I'll try drawing a rudimentary schematic to give a sense of its actual shape

    Steve, this is the first test. I read your post on resonant filter boxes & most of one of the links i think you shared to an old 2 stroke tuner guide, & I just thought about it & picked the bottle & how to cut it based on my intuition based on that. I bet it can be dialed in better when I get a chance. it feels like it's tuned for higher rpm then I'd actually intended, but I kind of like it that way
    Last edited: Oct 15, 2016
  7. Nate888

    Nate888 Member

    20161015_162527.jpg well, it ain't pretty, but I hope my sketches give a sense of what's underneath the 'mud wrap'
  8. Nate888

    Nate888 Member

    20161015_173906.jpg right side view
  9. jaguar

    jaguar Well-Known Member

    with a header that short I'll bet your engine can't rev high enough to get into the pipe powerband
  10. KTOKTO

    KTOKTO Active Member

    I think the doctor can get you a cream for that lump.
    Last edited: Oct 16, 2016
  11. Nate888

    Nate888 Member

    that's pretty much what I'd expected, but w/ this pipe, the engine feels like at speeds over 24 mph, it's putting out at least 50% more power than it did with either a straight pipe, or the slightly restrictive de tuned generic can muffler type exhaust that I tried.

    with the pipe & intake together it feels almost turbo charged. like the engine gets a second wind from roughly 35-45 mph (speeds are my estimates. could easily be 5 mph lower. & I really hope it's not 5 mph higher that I've been driving!)
  12. Nate888

    Nate888 Member

    I was looking at my intake & thinking it's probably a good 8 inches on either side of the carb. then I measured & found it's really only 7.5"

    some kind of innuendo to be made there for sure
  13. Nate888

    Nate888 Member

    the doctor was puzzled, "we normally only see this sort of thing deep in the tropical back country..."
    KTOKTO likes this.
  14. Neptunati

    Neptunati New Member

    Dude ziptie your phone to your stem and head tube. Download Ulysses spedo app. That way you can verify via GPS how fast your going. It's very accurate. I've gotten to 35 with my gt80 and stock flex pipe. 35 definitely felt like 40 for sure with no Speedo lol