Holyman Posted December 11, 2003 Report Share Posted December 11, 2003 Some of you may recall the old forum where I got a friend of mine { a former Princeton professor and who now works for the DOD} to comment on the lightened flywheel theories. I recently asked him about the boost bottle and whether there is science to show that it works. Here are his comments... Hi Dave - Hope you had a nice Thanksgiving break - I had a few days off from work which was pretty nice. I'm mainly into the design and optimization of turbine and rocket engines, but I have a little bit of experience with 2 stroke engine cycles: 2 strokes are very sensitive to intake and exhaust conditions since their simple passive design relies heavily on external components. The exhaust pipes are tuned and equipped with divergent and convergent nozzle sections to create a slight vacuum immediately after exhaust and a slight pressure right before the exhaust port closes. This helps to clear out exhaust gasses and to pull extra fuel/air through the chamber, then the reflected sound pressure wave pushes some of the extra fuel/air back into the cylinder, creating a slight supercharge. The exhaust pipe tuning has a very significant effect, approx. 10%-40% power gains for most engines, however, a mismatched exhaust can also reduce power. Boost bottles are more controversial with regards to performance gains. If the bottle is properly matched to the engine, it is likely that some gain in performance can be measured, but these gains are usually insignificant, perhaps 1-3 % peak under certain load and rpm conditions. Boost bottle theory: All 2 stroke engines equipped with reed valves tend to spit back a little of the fuel air mixture sucked into a chamber. The boost bottle stores this small amount of fuel/air in a tank along with additional air. After one chamber spits back a bit of the mixture, the other is just starting its intake, and boost bottle supporters claim the spitback from one chamber can pressurize the bottle slightly and force more mixture into the other chamber. Others claim that the sudden stop of flow of mixture into one engine chamber creates a pressure wave that would bounce back up the intake pipe unless it had a boost bottle to enter and pressurize, and the bigger chamber instead of a crossover tube reduces flow resistance between carbs. There are numerous other theories and claims regarding boost bottles, some are at least loosely based on scientific principles, but most of the gains would be slight and only at a few discreet operating points and rpm ranges. In conclusion: Properly matched boost bottles do produce some (barely) measurable gains over certain rpm ranges, but nothing really significant. Just enough to legally verify that it does produce a gain. Most of the boost bottle theory available on the internet is usually written or altered by people trying to sell boost bottles, so I wouldn't put too much faith in it. I don't know of any textbooks or sources that would contain scientific data - I don't think the performance gains have been significant enough to attract any serious research interest. I think most of these boost bottles fall into the same category as the "electric turbochargers" which have plagued the internet and ebay over the last two years. Someone decided that strapping a spraypainted $8 marine electric sewage vent fan into a car's intake system could increase performance since it acted as a turbocharger. They never mentioned that a real turbo can give 9-20 psi boost and the electric turbo provided only 0.008 psi, but just that a gain was possible. They along with hundreds of copycats sold thousands of sewage fan turbos for up to $400 each, but now the price has dropped to $15 due to market saturation and lack of demand or belief in the claims. In my opinion, if these boost bottles actually gave any significant gains, they wouldn't need to offer free shipping or <$30 list prices to get them to sell. The boost bottle probably won't hurt performance, and there might be some minor gains under a few situations, but I wouldn't recommend buying one unless you simply liked the way it looked on the bike or ATV. Hope this helps some, Joe Quote Link to comment Share on other sites More sharing options...
blk02banshee Posted December 11, 2003 Report Share Posted December 11, 2003 Good info Exactly what I was thinking...it might do somehting, maybe a small, un-noticeable gain, but not likely. If you think it looks cool, RUN IT. Is it worth anything performance-wise....probably not. Quote Link to comment Share on other sites More sharing options...
Proquad101 Posted December 11, 2003 Report Share Posted December 11, 2003 I used to run a boost bottle on my banshee but one day I was at a half mile race and blew the rubber grommet out on one side so I got walking cane tips and put them on my banshee, that gave me so much more throttle responce. I dont know if it will work like that on every bike but it worked good on my motor set-up. Quote Link to comment Share on other sites More sharing options...
Screamin_Banshee Posted December 11, 2003 Report Share Posted December 11, 2003 Dave, thank you and Joe for helpin clear this annoying topic up!! Very good info, im sure everyone will apreciate it, I know I do! Quote Link to comment Share on other sites More sharing options...
frocashmoney24 Posted December 11, 2003 Report Share Posted December 11, 2003 very interesting, its what ive heard quite a bit, but screw it i run with a 1 carb setup! Quote Link to comment Share on other sites More sharing options...
Dextreme Posted December 19, 2003 Report Share Posted December 19, 2003 When I bought my banshee (used) about 4 years ago, the previous owner had put a boost bottle on it. The day I bought the shee, I had it dyno'ed to dial in the jetting and check HP numbers. We ran two passes with the boost bottle and then ran two passes with a stock cross over tube. The end result was that the stock cross over tube produced about 1.8 hp over the boost bottle. So now my boost bottle is in the bushes somewhere. Quote Link to comment Share on other sites More sharing options...
98bonerSTOCKshee Posted December 19, 2003 Report Share Posted December 19, 2003 I used to run a boost bottle on my banshee but one day I was at a half mile race and blew the rubber grommet out on one side so I got walking cane tips and put them on my banshee, that gave me so much more throttle responce. I dont know if it will work like that on every bike but it worked good on my motor set-up. Proquad101 do you still run with those caps on? Quote Link to comment Share on other sites More sharing options...
Banchetta Posted December 20, 2003 Report Share Posted December 20, 2003 I dynoed my shee w/ and w/o and noticed an increase of about 2hp for about 1500rpms from whatever rpm that you hit the throttle from....so if your at 3000rpms and hit the throttle, then you'd see a 2hp increase w/ the stock tube from 3000rpms to 4500rpms... If you hit the throttle at 4000rpms, then you'd see a gain from 4000-5500rpms....needless to say, my stock tube is back on.... Quote Link to comment Share on other sites More sharing options...
ScreaminShee01 Posted December 20, 2003 Report Share Posted December 20, 2003 Where can i get mysel a stock tube??? i got a gay white brother boost bottle.... any help? Quote Link to comment Share on other sites More sharing options...
frocashmoney24 Posted December 20, 2003 Report Share Posted December 20, 2003 im sure someone would trade you, but ive heard if you block the holes they imporve even more Quote Link to comment Share on other sites More sharing options...
Proquad101 Posted December 21, 2003 Report Share Posted December 21, 2003 I used to run a boost bottle on my banshee but one day I was at a half mile race and blew the rubber grommet out on one side so I got walking cane tips and put them on my banshee, that gave me so much more throttle responce. I dont know if it will work like that on every bike but it worked good on my motor set-up. Proquad101 do you still run with those caps on? Yep, work good last long Quote Link to comment Share on other sites More sharing options...
98bonerSTOCKshee Posted December 24, 2003 Report Share Posted December 24, 2003 Proquad101 so what motor set up ypu running... I am stock except for add ons... I geuss I could just try and see what it does for me! Probably find out that I wasted $30... Quote Link to comment Share on other sites More sharing options...
Proquad101 Posted December 25, 2003 Report Share Posted December 25, 2003 Proquad101 so what motor set up ypu running... I am stock except for add ons... I geuss I could just try and see what it does for me! Probably find out that I wasted $30... I have 4mm stroker with a 5mm longrod crank,porting by passion racing engines, noss coolhead, 34mm pj carbs, dyna ignition, cpi pipes, my bore is 65.5, v-force reeds, and a few other little mods (top secret) If you have other ? about how your setup might work give me a shout, be happy to help. Later Quote Link to comment Share on other sites More sharing options...
Holyman Posted January 27, 2004 Author Report Share Posted January 27, 2004 bump Quote Link to comment Share on other sites More sharing options...
ledofthezep Posted January 28, 2004 Report Share Posted January 28, 2004 Good post, just now found it. Great info, is awesome to have extremely intelligent people to explain shit in a no BS way. From what I read though it does explain why the only thing I noticed when I put on my boost bottle was a bit better throttle response, this was with stock pipes, head milled .030 and my old K&N clamp ons. Hell, I shipped my stock crossover tube to someone on here for free so they could try it vs. their boost bottle, can't even remember who anymore.... Quote Link to comment Share on other sites More sharing options...
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