Mad Scientist Lab test - Boost Bottle

[Steve Best]

A boost bottle is a misnomer for what can only be a device (at very best) to improve idle quality. Other than that, it's a waste of time and money. Helmholtz resonators are primarily used to attenuate induction noise in automotive applications, and serve no purpose as a "power boost" device.

Boost bottle is a misnomer, you are right, but it has much more effect than just idle quality, which it did not affect on the DT200 or IT250 at all.
If you buy one of the colourful systems with the long 1/4" hose:

you are right it will likely be a waste of money. And you are sort of right that Helmholtz resonators are often used to attenuate induction noise, they are and it is an easy calculation for a filterbox, but they do indeed boost power in all the applications I illustrated above. I know this from hands-on A-B-A testing, not something I read or took a poll on a forum. YEIS worked, log/runner intakes work, plenum intakes work. All are Helmholtz resonators, a tube and chamber that creates a resonant frequency. None of the examples shown above are using them to attenuate noise.

Steve

 

[Deleted member 12676]

don't confuse Fabian with facts.
he has an unalterable opinion and he's going to stick to it.

 

[Deleted member 12676]

but don't take anything of what I say as advocating them.
for a one speed ride what is needed are things that increase power over the whole RPM range.
examples:
a good carburetor
a good air filter
widening the exhaust and intake ports
increasing intake port duration to 120 degrees
increasing engine compression
increasing spark power
having a CDI that has a more 2 stroke friendly timing curve

If you install things that give you a rush of power at the top RPM then you'll want to grab a higher gear but there isn't one to grab!

 

[Fabian]

don't confuse Fabian with facts.

There are times when a "laugh" emoticon is the most appropriate response, and this is one of those times.
Please humour me more!

 

[Deleted member 12676]

I just had the idea that to function as a resonator there may be a limit to how skinny or how long the tubing can be.
So I experimented with a 3.75" long 2.25" wide plastic bottle and with 1/4" inner diameter of tubing the maximum length was 3 inches. Longer than that and I couldn't get any reverberation when blowing across the end of the tubing.
I wonder if tubing length has been the unknown critical factor separating successes from failures.
I don't have 3/8" ID tubing but I'll try to get some to test its critical length.
If any of you have a boost bottle then disconnect the tubing from the intake manifold and blow into it at an angle to see if it will reverberate.

 

[Deleted member 12676]

Look at the picture in this forum post of a boost bottle on a Yamaha trials bike. It used a large diameter tubing that looks to be no more than 4 inches long:
http://www.trialscentral.com/forums/topic/11261-ty175-boost-bottle/

Look at how large a diameter the tubing is from a Yamaha RX115 (although the cylinder shown is from Suzuki AX100 which he was trying to adopt it to):
https://i.ytimg.com/vi/BihrR3ObG1U/maxresdefault.jpg

This article shows some factory motocross racing bikes with boost bottles. Normally the tubing is wide and short.
http://motocrossactionmag.com/news/mxas-gyro-gearloose-invention-of-the-day-4

Yamaha invented the boost bottle system. Here’s some history:
On June 30, 1980, Yamaha announced two new energy-saving engine system technologies that it had developed independently: the Yamaha Induction Control System (YICS), a technology for 4-stroke engines, and the Yamaha Energy Induction System (YEIS) for 2-stroke engines.
YICS reduced the amount of fuel consumed by speeding up intake charge to the cylinders, reducing combustion time, and increasing combustion efficiency. This technology made it possible to create energy-efficient, low-cost engines.
In testing on actual motorcycles, it was confirmed that fuel was conserved by around 10%. Development focused on 2-stroke engines, but the technology could also be applied to 4-stroke engines. YEIS was first used on the YZ motorcycle in 1980, then on four 2-stroke models in 1981.
http://global.yamaha-motor.com/about/history/stories/0019.html

Here’s the patent on the YEIS but the full paper will cost you $26.
http://papers.sae.org/810923/

The previous comment I made about boost bottles and reed valves only pertained to having the tubing connect past the reed valve. Reading up on this topic I see that it was meant to be placed before the reed valve and with that placement it can have the same function as it does on engines without a reed valve.

 

[Deleted member 12676]

to answer piecepatrols question- some things you can do to a 2 stroke benefit the top RPM power while robbing from the low RPM power, and vice versa.
So if you installed a boost bottle and it robbed Peter to pay Paul then it's not a carburetor problem. You have to adjust the boost bottle so you don't lose so much high RPM power, by shortening the connecting tubing. Please cut it in half and then report back.

 

[Deleted member 12676]

I just tested 5/16" ID tubing connected to a bottle and it would reverberate up to 15 inches in length.

 

[Deleted member 12676]

If you want me to analyze your boost bottle then tell me:
the bottle volume
the distance from bottle neck to intake manifold
the inner diameter of the connecting tubing

 

[Deleted member 12676]

I think all boost bottles serve to enhance very low RPM power* by increasing intake tract volume, but only those that maintain these requirements also act as resonators to affect power at mid to high range RPM:
if the connecting tubing is 1/4" ID then it must not be over 3" long.
if the connecting tubing is 5/16" ID then it must not be over 15" long.

* see you tube video