Helmholtz Resonator or boost bottle

[best]

Hey guys, I've got the boost bottle off of Neil's DT motor and I am going to publish the top secret specifications:

Volume of the bottle is 200ml (or 200cc)
Neck is diameter 0.312" and length is 1.150"

You can read all about Helmholtz resonators at:
Helmholtz Resonators
for all the calculations, and you may find more simplified equations somewhere else.

So if you'd like to use this calculator:
Helmholtz Resonator Calculator
You would use the values:
Volume = 0.0002 Meters cubed
Port area = Pi ((0.312"X25.4)/2)X((0.312"X25.4)/2)/(1000X1000)= 0.000049 Meters squared
Port length = 1.150"X25.4/1000 = 0.02921 meters

So frequency is 158.3 Hz or 9498 cycles/min

This does not translate directly to RPM, because port opening and reed valve pulse cycles are involved.
I'd simplistically suggest about half the frequency would represent tuned rpm.

Anyway, this gives you an idea of what it would take to build your own Boost Bottle.
I'd suggest sticking close on frequency but going bigger on port area and bottle volume.

For example an 800ml bottle with a 1/2" neck 3/4" long would give about the same frequency, and probably a stronger signal. Remember, the bottle has to be rigid.

Anyone got time to try this?

Some info, you judge how good:
Boost Bottle - Wikiscootia - A scooter wiki
Boost Bottle Theory
Mini ATV Parts Intake Parts (looking at the math, I cannot see this working)
UNIVERSAL CUSTOM CC BOOST BOTTLE KITS
49ccScoot.com : Homemade Boost Bottle Information

 

[DirtDiggler]

Boost Bottles were invented for the Pocket Bikes when they became popular , 2 stroke engines without reed valves so there was nothing preventing fuel and air being blown back thru the carb during off throttle moments , My bro at work who was one of the original inventors spent a lot of time getting them sized correctly for the motors . He made a killing on them , but copycats bought his stuff and made their own and saturated ebay and other markets . They really don't do anything for a reedvalve engine , but for the non reed engines from what he said and others that rode the pocket bikes when they were popular said it was like night and day between the non boost bottle and the boost bottle mod. Hell if you like the looks of them go get some pvc pipe , 2 end caps , glue them on add a hose barb and clamp it on your bike and paste a sticker to it , might add that " Intimidation " Factor

 

[best]

Blastard, your brother would have been a very young child when Yamaha started putting boost bottles (YEIS) on its reed valve 2 strokes back around 1980. I think your brother probably re-started a trend with a non-current idea. There is nothing new under the sun it seems. Dr Helmholtz died over 100 years ago, and his resonator has been around as long as people have been blowing into jugs. Most fuel injected plenum type intakes use this tuning and it was the deal behind spacers on the single plane V8 intakes, whether we realized it or not at the time.

None of the other makers picked up on this, and Yamaha seemed to drop the boost bottles. why? Death of the street driven 2 stroke, cost cutting, not needed on full throttle race bikes, who knows. They did work. It is a simple technology and so easy to copy.

Hey, more picts of DT stuff including boost bottle in this old thread:
http://www.blasterforum.com/engine-mods-swaps-129/check-out-my-new-score-36811/index4.html

And then there is this explanation of powervalve and boost bottle in french:
(I can translate, it says "Yamaha works good". French always takes more words!

If google translate doesn't work for this I can translate, but it is a lot of typing.

With increasing the hp by increasing the rpm, mid-range suffers. I think a boost bottle may help.

Steve

 

[DirtDiggler]

LOL My " Brother " at work just turned 50 years old , and back in the early 80's when the non reed valve 2 stroke pocket bikes became popular , thats when HE started making boost bottles for them to cure the stumbles and off idle throttle response of the engines . For a reed valve motor they do nothing but split intakes and create air leaks .
The crossover tube on a Banshee does the same thing , it is just there to provide a pre-atomized charge of fuel to fill in the gaps in the jetting , you know something , anyone with a shee has also tossed it in the garbage because it's useless .
Now if someone machined a spacer plate with a tapped fitting that went between the reed cage and the intake , and that tapped fitting had a small hose and a bottle container at the end that was constantly being pressurized and then discharged , now that would possibly provide a gain in acceleration out of hard braking or coming from a hard drift into a straight away . The end result is something that only the assdyno will be able to tell and even then it may just be the rider " thinking " that it helps . I may have to make a prototype and sell it to someone here and have them chime in .

 

[best]

LOL My " Brother " at work just turned 50 years old , and back in the early 80's when the non reed valve 2 stroke pocket bikes became popular , thats when HE started making boost bottles for them to cure the stumbles and off idle throttle response of the engines . For a reed valve motor they do nothing but split intakes and create air leaks .
The crossover tube on a Banshee does the same thing , it is just there to provide a pre-atomized charge of fuel to fill in the gaps in the jetting , you know something , anyone with a shee has also tossed it in the garbage because it's useless .
Now if someone machined a spacer plate with a tapped fitting that went between the reed cage and the intake , and that tapped fitting had a small hose and a bottle container at the end that was constantly being pressurized and then discharged , now that would possibly provide a gain in acceleration out of hard braking or coming from a hard drift into a straight away . The end result is something that only the assdyno will be able to tell and even then it may just be the rider " thinking " that it helps . I may have to make a prototype and sell it to someone here and have them chime in .

They do work Blastard, I have tried it on and off the DT200, and back in the day we played with them off and on various IT Yamahas to feel the effect, all reed valve engines. Mid-range, slight boost, as reported by the ass dyno!

I do believe NASCAR teams used similar pulse phasing to get more air than theoretically possible to pass through the carb restrictor plates they were mandated to use.

Heck, if we used a lightweight pneumatic cylinder we could move the piston to change volume to move with the rpm range to keep it always in tune! Just hook it up to the YPVS cable.

 

[DirtDiggler]

The end result is the same , maybe a small fractional difference in air turbulence and atomization of the air/fuel/oil coming into the motor , which is designed for smoother throttle response . You still have to gage that against added fittings that may lead to a air leak and a damaged top end/siezed piston. Its a Widget , the product of a over active engineers imagination , and my experience with engineers is they have VERY LITTLE practical experience but all the time in the world to pour over theory .
All the research , all the R&D and all the $$$$ spent on a " Boost Bottle " can be eclipsed exponentially with porting and proper jetting .
It's a waste of time .