Trying to figure out how the Boost bottle works. I have been turning a wrench on small engines for about 40 years and thought I could reason just about anything to do about them out. Now I am really puzzled. I put my first bike together (classic 2 stroke 66cc china motor) on a Schwinn cruiser. It's been a bit cold to put many miles on it, but I have been riding it to work out the bugs (maybe have 50 miles on it). I bought a Boost system for it but didn't install it because I read that it was a waste of time. Today I rode it to town (about 15 miles) against a strong head wind and wasn't really impressed with the way it performed. I got home and installed the Boost Kit just because I had it and had some time. I don't really know if I gained any power, but it sure did make the thing run smoother. I had to turn the idle way down ( seemed way more touchy that way) but got it to run way better. I don't understand how the stupid thing works. Or why it works. Anyone??
Boost bottle
- Thread starter thdrduck
- Start date
I think it runs off the principle of helmholtz resonators (http://en.wikipedia.org/wiki/Helmholtz_resonance). Supposedly, the resonance of the air in the bottle will help prevent blowback out the intake port by a small amount which would improve performance by limiting the loss of your intake mixture out of the intake port when the piston is desceding.
From my experience boost bottles offer no performance gain and are simply a placebo.
From my experience boost bottles offer no performance gain and are simply a placebo.
Boost bottles are a waste of money. These little engines don't put out enough power to boost anything. Match the ports and get a 18mm Mikuni with the straight intake manifold. And a good pipe
I know I am not imagining the improvement so there is no placebo effect. I am sure that a different carb would do way more for that little engine then a small bottle with a plastic hose stuck to it, but I had the bottle and not the carb. I still don't see how it can do anything. My one concern is that this thing is connected to the intake so if it contains any fuel, it will be mixed with air and should there be a backfire (not likely, but could happen) would I not have a small bomb between my legs? Ouch! Anyway, it's on and will stay there until I have a reason to take it off. Looks like rain today so I guess it stays in the garage.
This is MY take on a boost bottle..
First I DON'T see and extra performance from one.
Second I do see a difference in the idle. I get a smoother idle at a lower RPM setting. That saves fuel, if I really cared.
I feel that matching the bottle cc to the engine cc makes a difference, although I haven't tried bottle that was too small or one too large.
When attaching the nipple to the intake, I make sure that the nipple doesn't impede the fuel flow from the carburetor.
I make my own and wouldn't waste the money that distributors charge for one. They are very easy to make, and very inexpensive if you have the tools.
First I DON'T see and extra performance from one.
Second I do see a difference in the idle. I get a smoother idle at a lower RPM setting. That saves fuel, if I really cared.
I feel that matching the bottle cc to the engine cc makes a difference, although I haven't tried bottle that was too small or one too large.
When attaching the nipple to the intake, I make sure that the nipple doesn't impede the fuel flow from the carburetor.
I make my own and wouldn't waste the money that distributors charge for one. They are very easy to make, and very inexpensive if you have the tools.
So is the bottle volume suppose to be 66cc including the hose?
My friend is running a boost bottle. He isn't noticing any extra performance so far, but his idle changed. (for the worse)
I'm thinking if it has the capability to change the idle, it should have the capability to change the performance.
Just like any tuning changes, get it right and you get an improvement. Get it wrong, and you loose performance. Or in our case a third option might be possible. The gain is so slight, it's difficult to tell the difference.
My friend is running a boost bottle. He isn't noticing any extra performance so far, but his idle changed. (for the worse)
I'm thinking if it has the capability to change the idle, it should have the capability to change the performance.
Just like any tuning changes, get it right and you get an improvement. Get it wrong, and you loose performance. Or in our case a third option might be possible. The gain is so slight, it's difficult to tell the difference.
I measured the bottle it self to exactly 60cc. The gain is in fact slight and that's why I don't recommend BUYING a factory boost bottle. They are so easy to make. I have a new bottle but haven't bothered to post it in my store.
