Homemade Boost Bottle

I am way more of a newbie than you, K, and not even close to a mechanic. I stumbled upon motorbicycling, and I'm not a mechanic. I live just outside the district in Silver Spring. I'd like to understand what you did, but I don't comprehend the whole boost thing at all. I've bored out my intake manifold and exhaust port and found the bike to run smoother, with less vibration, more low end torque, but not more top end, which I'm not after anyway.

It's my first bike, and I don't take much credit for it. A friend pressured me into buying the used beach cruiser from a Hispanic pawn shop in Takoma Park, and I added the motor. There aren't many of us here in DC with motorbicycles. Share the wealth, eh, brah?

You may find this of interest;
http://motorbicycling.com/f51/mad-scientist-lab-test-boost-bottle-86.html
http://motorbicycling.com/f13/boost-bottle-12241.html
http://motorbicycling.com/f13/boost-bottle-3398.html
http://motorbicycling.com/f4/boost-bottle-nos-kit-5109.html

Kinskeys said:

I made a Boost bottle from a old used butane gas aluminum can(5.7oz, 162gm) that I spray painted silver, then I tap and die a hole in the intake and in the top of the can, then I threaded in a 1/8" brass barb fitting in each, then attach the bottle with zip ties under the gas tank ,and connected the can and intake with a hose. Before the boost bottle I top out at 30.5 MPH and after I just top of at 34.8 MPH. Well I'm headed out to do some more riding, because I live downtown Washington, DC and there's too much traffic during the day to really have fun, so I'll post some pictures later on & update you if I went any faster.

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I should'a read the whole pile of posts here before I repeated my inquiry that you answered. i will be watching for your further comments as soon as my throttle issue is resolved
Thanks

yodar

K,

You are in the minority, it seems, for those who have or have tried a boost bottle. Your detailed explanation indicates you really know what you're talking about though.

I should clarify that I did not touch the cylinder, but only did port matching of the intake manifold and the muffler. The stock holes were circular, but the ports on the cylinder are elliptical. I figure, unscientifically simply by eyeballing them, I increased the openings about 40-50%. And I didn't worry about getting them perfect. I figured anything was an improvement over the crude manufacturing of the stock stuff. And I was right.

You said your top speed went up. What kind of low end power change did you experience, if any? I would like to not pedal going up hills, that's all. I don't want to go any faster. It's just a beach cruiser; it's not meant to go the 30mph I'm approaching.

I'm rarely downtown, but your offer is interesting, and if ever I'm motivated to throw the bike on the rack and take her downtown, I'll be sure to call you.

I don't care what you say... boost bottles don't really work on these HT engines; & they sure as heck don't give that kind of top end power!!

You're engine is still probably just breaking in. (& running better as it goes), Or just running better due to more suitable weather.

Kinskeys said:

I made a Boost bottle from a old used butane gas aluminum can(5.7oz, 162gm) that I spray painted silver, then I tap and die a hole in the intake and in the top of the can, then I threaded in a 1/8" brass barb fitting in each, then attach the bottle with zip ties under the gas tank ,and connected the can and intake with a hose. Before the boost bottle I top out at 30.5 MPH and after I just top of at 34.8 MPH. Well I'm headed out to do some more riding, because I live downtown Washington, DC and there's too much traffic during the day to really have fun, so I'll post some pictures later on & update you if I went any faster.

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5.7 Oz computes, because one resource told me the bottle should be ~50 cc and that is slightly less than 6 fluid oz.

But your bottle LOOKS much bigger, looks like a good 12-16 oz.

Is this 50 CC guide real ?? correct me on the apparent "bigger-than-50 CC -perception" given by your excellent picture

thanks!

yodar

Kinskeys said:

Hi C, It's function is to absorb & release pressure pulses within the intake vein, assisting engine breathing. Now an explanation of exactly what goes on involves a lot of physics and a good understanding of fluid dynamics & pressure zones, but can be explained rather easily. During the intake stroke, air is sucked through the intake manifold and into the port at a considerable velocity. Because of this velocity, the air is said to have relative inertia. Now, when the intake valve closes, the kinetically charged air suddenly has nowhere to go, creating a high-pressure area. Naturally, the air wants to release its pressure in the easiest way possible, so it tries to shoot back out the way it came, creating a pressure wave in the opposite direction we want it. Then no sooner dose the wave begin to travel, the intake valve suddenly opens again leaving the motor to try and pull the pressure wave back in again. This dramatically effects low RPM, wastes energy and kills low-end performance. Now the same engine, but with a BOOST BOTTLE. Air goes whistling down the manifold until the intake valve closes. The air, still all charged up with energy tries to escape back up the manifold but is met with a small port that has a residual vacuum. This vacuum being caused by the previous suction of the intake stroke, sucks most of the pulse inside the Boost Bottle, storing much of the pulse’s energy. The intake valve then suddenly opens, creating a low-pressure area outside of the Boost Bottle. The gasses then shoot out of the Boost Bottle, directly into the intake system as a pressure pulse, instead of having to be pulled in by the piston. More air is then also pulled in from the manifold to completely fill the cylinder… Thus giving you an additional boost of power. If your ever downtown give me a call 202-520-1115 and we can go grab a cup of coffee, and if you help port my intake & exhaust, I'll help you make a boost bottle.

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Two stroke engines dont have valves. lol nice try

nidyanazo said:

Two stroke engines dont have valves. lol nice try

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I'm glad someone else caught that too.
And that 'butane' canister looks a lot shorter and fatter than the ones I have.
Once again, I'm smelling rodents and playing the BS card.
Nice job of copy and paste too from this site: http://sites.google.com/site/motorizedbikes101/boost-bottle

Noobs! Sheesh

nidyanazo said:

Two stroke engines dont have valves. lol nice try

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So what about four stroke?

Would it have any noticeable effect on them?


Not challenging you, just trying to learn more

nice boost bottle

some 2 stroked do indeed have valves.
I had an old 2 stroke minibike which had valves, it was exactly like a 4 stroke in design, but the cam lifters simply had 2 lobes each on it instead of the one that 4 strokes have.

nidyanazo said:

Two stroke engines dont have valves. lol nice try

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The intake and exhaust ports function the same on a 2-stroke as valves do on a 4-stroke. The only difference is that the piston is the valve on a 2-stroke.

Question: How on earth do people honestly think that any signifigant amount of air is gonna make it through that 3/8" ID tube (at best) to the bottle?

Has anyone here tryed making a boost bottle with a nice short 3/4" or larger hose to it?

Anyone else here port matched the intake and realised that even a little bigger is WAYYY better? So why do people use such tiny hoses on the boost bottle?

A funny little about using small diameter tubing for connecting boost bottles....I used to use clear surgical tubing on mine. After installing and resetting the idle and air/fuel mixture and getting it all dialed in, while sitting with the engine idling I'd pinch the tubing with my fingers and it would kill the engine. I'm serious. I found that surgical tubing worked much better than tubing with a higher durometer (stiffer).

Here's a cut and paste....and interesting read....

Boost Bottle

How does a Boost Bottle improve performance? Air rushes thru the carb on the intake cycle. Ignition accelerates the piston down, forcing the reeds to snap shut. The momentum (inertia) of the air has to go someplace. It goes back thru the carb causing a double rich mixture. The result can be rough idle or hesitation.

Due to the high velocity of the fuel air mixture through the carb boot, we need to take advantage of this momentum/inertia energy. The Boost Bottle and tube provide storage for the fuel air mixture between carb boots. The energy (pulse) forces the pre-atomized mixture in the tube from the previous cycle into the adjoining carb boot where the reeds are just opening and ready to receive the fuel air mixture. The boost bottle and tube provide a "boost" supercharge effect to each cycle.

The boost bottle is most effective at lower and mid-range rpm, and, when you are on & off the throttle. It assists in filling the cylinder (shorter distance) for a fraction of a second until the carburetor venturi gets enough velocity to fully atomize the fuel. The advantage is that it brings up the torque and horsepower in the bottom of the rpm range, up to where the pipe(s) starts to work. There is a small benefit at high rpm's.

What Size? Singles = usually the CC of one cylinder or larger. 700cc Twins = 300cc boost bottle. 700cc Triples = 225cc.

Variables: Engine CC's, Carb Size, RPM below pipe, Number of cylinders. Large carbs like larger bottles/tubes. Triples like smaller due to less time between pulses. I use the TSR computer software to calculate the Boost Bottle for a specific set up.

Yes they work, when the size is right, the inertia of the air is stored like a spring in the boost bottle to help charge the next cycle. Try tuning a Yamaha Phazer without it's boost bottle!

Power valve engines may not have similar performance gains because the valves will keep the bottom end crisp. Testing w/ powervalves will probably show gains off idle and low bottom end. Is it worth it?? That depends on what you are willing to pay for some torque and a couple of horses!

it just smoothens the ride, and higher revs lol thats what mine did. i wasn’t really looking for power anyway, i wanted it because of what it actually did, not what people claim it to do. i was happy with outcome

Kinskeys said:

Hi C, It's function is to absorb & release pressure pulses within the intake vein, assisting engine breathing. Now an explanation of exactly what goes on involves a lot of physics and a good understanding of fluid dynamics & pressure zones, but can be explained rather easily. During the intake stroke, air is sucked through the intake manifold and into the port at a considerable velocity. Because of this velocity, the air is said to have relative inertia. Now, when the intake valve closes, the kinetically charged air suddenly has nowhere to go, creating a high-pressure area. Naturally, the air wants to release its pressure in the easiest way possible, so it tries to shoot back out the way it came, creating a pressure wave in the opposite direction we want it. Then no sooner dose the wave begin to travel, the intake valve suddenly opens again leaving the motor to try and pull the pressure wave back in again. This dramatically effects low RPM, wastes energy and kills low-end performance. Now the same engine, but with a BOOST BOTTLE. Air goes whistling down the manifold until the intake valve closes. The air, still all charged up with energy tries to escape back up the manifold but is met with a small port that has a residual vacuum. This vacuum being caused by the previous suction of the intake stroke, sucks most of the pulse inside the Boost Bottle, storing much of the pulse’s energy. The intake valve then suddenly opens, creating a low-pressure area outside of the Boost Bottle. The gasses then shoot out of the Boost Bottle, directly into the intake system as a pressure pulse, instead of having to be pulled in by the piston. More air is then also pulled in from the manifold to completely fill the cylinder… Thus giving you an additional boost of power. If your ever downtown give me a call 202-520-1115 and we can go grab a cup of coffee, and if you help port my intake & exhaust, I'll help you make a boost bottle.

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When did they start putting intake valves on two strokes???? lol--Get a 18mm Mikuni and one of Jim's straight intake manifolds and a good expansion chamber, match the ports and open up the straight intake for the bigger carb. You will think you added nitrous. Also get one of Jim's billet heads if you can and a 34 tooth rear billet sprocket kit from him or Pirate's..Boost bottles..DEAD WEIGHT..

na im with the good big bottle croud knew y it should work and mine seem happyer with one

Venice Motor Bikes said:

I don't care what you say... boost bottles don't really work on these HT engines; & they sure as heck don't give that kind of top end power!!

You're engine is still probably just breaking in. (& running better as it goes), Or just running better due to more suitable weather.

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I agree 100%..Spend your money on a straight intake manifold and a 18mm Mikuni or use your stock carb as well as a basic expansion chamber and do the basic port match-up. Get a Manic Mechanic slant head IF you can (Jim #1 in my book). As I said in other posts boost bottles are dead weight.