boost bottle effective on non reed type motor?

Discussion in '2-Stroke Engines' started by Nitropeewee, Jun 22, 2009.

  1. Nitropeewee

    Nitropeewee Member

    read through some posts on here n was wondering if these are really efcctive on the non reed type motors. all the info ive found goes something like this "

    Basically what happens is this, your piston is in an upward position and once the carb sucks in air producing a gas air mixture an explosion occurs above the piston causing it to go down which forces the reeds to shut. In this process there is a air well more like a gas air mixture pushed out the carb. What the purpose of the boost bottle is to capture this double rich mixture and feed it back into the carb in the next cycle. This provides a supercharged effect.
    So ok if you are mechanically inclined you will know this can not possibly go smoothly and requires some calibration to make things work right. Unlike the websites out there trying to sell you the boost bottles you have to know what to look for before spending $30 or more for one or even two.

    so dos it work on a motor without the reeds?

  2. Old Bob

    Old Bob Member

    For some reason there is a myth circulating the internet that boost bottles only work with reeds, well nothing is further from the truth.

    The description above is some what off, but the idea the bottle captures and store A/F mix is correct.
    The calculations for determining bottle capacity, location and bottle inlet/outlet tube are fairly complicated. The bottle also only works in a narrow rpm range making matching expansion chamber,port timing and gearing even more critical.

    A search of the web may turn up the info I had it some where but can't find, in the long run if have enough information to determine if a commercaily made product will work for you, then you have enough information to do it on your own.
  3. 2stroketech

    2stroketech New Member

    Boost bottles do nothing for a well designed piston port engine. On an engine that has poor port design and timing; then yes a boost bottle will help elieviagte some of the symptoms of poor design. However it is much better to fix the problem then trying to throw a bandaid on it. Also a boost bottle will not allow you to set the intake harmonics.
  4. Old Bob

    Old Bob Member


    The principle of boost bottle function is to work WITH intake resonance.

    piston port engines have the worst kind of spit back condition out of all the induction types used on two strokes, they benefit the most from the bottle.
    Boost bottles are nothing more than a helmholtz resonator.They are unaware of reeds disc valves or piston port controled intake events. They respond to volume, frequency and pressure.

    The biggest reason boost bottles have the bad reputation that they do is, is that very few people understand the physics and how to apply them.
  5. if you have a reed motor you dont need a boost bottle because the reeds close before any blow back can happen.people with non reed motors can use a boost bottle,but my engine likes to run just the way it came.
  6. linnix13

    linnix13 Member

    not sure but i have a HT 80cc and threw a boost bottle on it and it makes the engine run smoother and get to higher revs without huge vibration, it definatly works on the cheap engines, but once your done riding and you turn the engine off their is fuel residue in the bottle that runs down into the carb and floods the engine so its hard to start it once your parked it for a few hours.
  7. 2stroketech

    2stroketech New Member

    A boost bottle is nothing more than an expansion chamber to disopate the power of the harmonic wave.

    If timing is right in the first place then you would not have problem with spit back.

    OH and here is the great part; if you time the harmonic wave properly then you can pack the crank case better than 1 atmospheric preasure.

    If you are experiencing heavy blowback then your intake timing is too low. You will either need to extend the skirt of your piston on the intake side or raise the bottom of your intake port. The third option (although much trickier, but will increase pwer) is tune your intake harmonics by lenth of intake track before and after the carburetor.

    Tuning your intake harmonics can give you as much as 20% in HP. Not as much as a tuned pipe on the exhasut, but still very healthy gains.
  8. Old Bob

    Old Bob Member

    Heavy spitback is caused by high timing, 150+ duration.
  9. 2stroketech

    2stroketech New Member

    I was describing physical placement of the intake floor. I figured using actual timing numbers might be a bit much for some in this conversation.

    If a person wants to use a boost bottle; I say go for. I was not trying get in any ones way or step on anyones toes.

    Good luck with your projects.
  10. why not just add a reed valve on the intake.
  11. Nitropeewee

    Nitropeewee Member

    wow lots of good info thanxs everyone! think ill go fer it!