Boost Bottle in Operation

[biknut]

I thought this was interesting. In this video you can see what's actually happening in a boost bottle as the intake pressure changes.


http://www.youtube.com/watch?v=y80MOk3IpSs&NR=1&feature=fvwp

 

[Bikeguy Joe]

All that shows is an increase in vacuum when the throttle is opened.

 

[biknut]

All that shows is an increase in vacuum when the throttle is opened.

Yes, it does show that the vacuum increases when you open the throttle, because the balloon does get smaller, but I think it shows a little more than that. It also gives you a visual of how much change in pressure there actually is between open and closed throttle, and I think that might give a clue as to how much volume a boost bottle might need for maximum effect.

It looks like that's not going to be much volume. Most of the boost bottles I've seen look like they're probably too big.

Also using a balloon inside a bottle gives me some ideas. I wonder the effect the balloon has from expanding when the throttle is closed, and what effect the pressure in the balloon has on the tuning when opening the throttle and letting that pressure escape back into the intake.

Of course my theory could just be crack pipe, in mean pot.

 

[moonerdizzle]

a proper boost bottle is supposed to be the same cc as the cylinder. so on a 66cc engine, the volume of the intake, from the piston skirt to the carb slide, and the total volume of the boost bottle and hose for the boost bottle should be 66cc. i dont know how much of an effect having too large or small of a boost bottle is, but i agree, most boost bottles ive seen for sale are too large

 

[16v4nrbrgr]

That video shows vac decreasing when the throttle is opened,, see the first comment and the rest position of the balloon with the motor turned off. The Ballon actually was impeding the proper functioning of the bottle, because you want the bottle to release its charge on the open intake strokes or when the reeds are oscillating at the open point, the effect is harmonic, and something you can't see like in the vid. The point is to save the fuel charge from the closed part of the cycle and force it back in when it opens again instead of it just hitting the closed port and possible re-liquifying.

I think to retain the harmonic resonation the bottle and line should be hard like aluminum or brass or something. The ones for Banshees are aluminum.

I was thinking a old butane bottle might make a good boost bottle, it's about 300cc, you need it to be a multiple of the displacement for a harmonic boosting to take effect I have read. It's wave superposition tuning. Suppose it would work for a 50?

 

[moonerdizzle]

http://www.pro-tecperformance.com/msban2.htm

cc of one cylinder, not multiples of a cylinder

 

[moonerdizzle]

"The main criteria for boost bottle design is that the bottle be at least as big as the displacement of the cylinder and the hose cross section be at least as big as the throttle opening at the intended RPM. The information on this spreadsheet was taken from Yamaha's SAE paper # 810923, 'Modification of Two-Stroke Engine Intake System for Improvements of Fuel Consumption and Performance through the Yamaha Energy Induction System', by Noriyuki Hata, Takeo Fujita and Noritaki Matsuo, Sept. 1981." is writen in a cell.

 

[Kioshk]

There should be a parental advisory on this vid. Rated-R.

 

[16v4nrbrgr]

So then an old Ronson butane can would work?
Hey check this out:
http://www.google.com/url?sa=t&rct=...sg=AFQjCNGc6yPdEXCO_4zyd1lvJzRy7C7cNg&cad=rja
not sure how accurate the calculations are but here's something.

 

[k.mah]

Awesome vid! I always thought the pressure or vaccuum built was MUCH smaller than what was shown. Maybe they aren't just for 100% show, as I previously thought....

 

[Venice Motor Bikes]

I've always read that a boost bottle is supposed to be the exact same cc's as the intake manifold & port. :/

 

[Greg58]

Looking at the video I wonder if he had holes in the cap so the balloon could expand or was the pressure equalizing and stopping the expansion.

 

[Frogster]

Looking at the video I wonder if he had holes in the cap so the balloon could expand or was the pressure equalizing and stopping the expansion.

thats what I was thinking about when i watched the video too.

I personally have no experience with them, but boost bottles seem to be a pretty debated topic when it comes to engine performance.
The physics and scientific logic behind how they work makes sense. However I think it really is a bit more complicated then most people who buy boost bottle kits can understand. In my opinion to get gains from a boost bottle, you would have to have a serious understanding about the physics of the engines intake, and find the best setup through trail and air. Also, to convince anyone effectively, you would need to have dyno sheets to backup any claim that you had gained hp and torque from your boost bottle intake.

 

[placidscene]

Frogster, did you say "Trial and Air" on purpose? Because that is perfect for this thread! lol

 

[Frogster]

lmaoo noo... i did not mean to say that, i meant trail and error.

Lol well thats embarassing

 

[biknut]

I think the main question about a boost bottle that's never been adequately answered is, does it suck, or does it blow?

 

[happycheapskate]

It's a vaccuum bottle. If the bottle is large enough, the hose pathway open enough, and the fitting plumbed so that incoming air has an induction effect on it, the bottle will store a vaccuum pulse that synchs with the engine's frequency. It doesn't blow anything.
There is an added effect that the vacuum sucks some fuel mixture in, which is atomized and redistributed to the engine.

I'll make some more videos to compare it with a stock engine and with a loud weedeater, but here is mine, a Tanaka 33cc with a large vacuum bottle and 1/4 fuel hose line, about 8".
You can here at about 14:30, the engine running under light load, going about 10mph, just the point where the clutch is fully engaged (which is why I have to keep backing off and then gassing, to pace with the cyclists. The engine makes a 4stroke sound a little at the lower RPM, but before the bottle addition at that RPM it was rattling and not powerful. Now it will pull well and throttle control is smooth instead of On/off.

19:30 you can hear the engine pulling uphill at a low RPM http://youtu.be/VZTpH75jJ1c?t=19m36s

Here is the engine in its normal operating range http://youtu.be/VZTpH75jJ1c?t=26m37s but not WOT up hill (don't want to fly into stalled cyclists at top of hill)

If you could put your hand on the vacuum bottle, it would be warm to the touch but not hot, from being near the engine fins. You could feel the vacuum pulses. The idle is much smoother than the stock (my wife has the same engine on hers)PF3300, and has a lot more guts at low RPM. Vibration is reduced, especially at idle and lowRPM.

I think the main question about a boost bottle that's never been adequately answered is, does it suck, or does it blow?

 

[happycheapskate]

If someone has a dyno, they can test my puny 33cc on it. lol You could see what happens by putting a 1" hose and plug on it instead of the bottle. The carb is untunable EPA style.

 

[happycheapskate]

http://www.youtube.com/watch?v=qIKrh0h7Wsc&feature=youtu.be

Here is a ride video on mostly flat ground and slight inclines through the city.

 

[16v4nrbrgr]

Very cool, thanks for the input HCS. Glad to hear that it worked to smooth out your midrange on the 33. I have an old stainless water bottle I was thinking about sticking on an intake since it got moldy inside and isn't fit as a drinking bottle anymore. My 52 cc auger motor is very similar to that tanaka except the top end, so I bet a similar setup will help make the motor more torquey, which will be great for the trials BMX that I am making for it.