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High Performance Bicycle Engine Tips and Motorized Race Bicycles We all want our bicycle engines to push our bikes faster. Get exclusive engine modification tips and suggestions from us. Also check out some of our racing members builds

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  #11  
Old 03-01-2015, 04:03 PM
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maniac57 maniac57 is offline
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Default Re: Modded Boost Bottle

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Originally Posted by snorks View Post
So there is no tuned inlet tract length for motors with reeds? Ive always thought rotary disc valves were superior to reeds.....just trying to think why exactly.....
I have also often thought that so called boost boottles have a very small diameter connecting hose? I would nave thought the opening should be bigger.

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The reason disc valves were so much more powerful was that a disc allowed MUCH longer intake duration which makes for better transfer flow from a higher pressure charge in the cases. Also allows better control over intake timing and more aggressive port timing.
Remember the sick Rotax case induction disc valves? Those engines had almost TWICE the power of the same displacement if piston ported. But they were EXTREMELY violent and had a BRUTAL hit which was harder to ride fast.
Only the very best riders could use the hit to actually go faster. most just flipped over backwards or lost traction.
While I LOVED my Can Am's, even I have to admit, it was NOT fun to ride really hard....you really had to be assertive and think ahead. When that power hit, you better be pointed in the right direction, 'cause you were going that way RIGHT NOW!!
Plus it's damned hard to steer with the front wheel in the air all the time....
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  #12  
Old 03-05-2015, 06:15 PM
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cannonball2 cannonball2 is offline
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Default Re: Modded Boost Bottle

Ok finally got the check valve from the snow bound north. Had already modded the intake so it only took a bout 10min to get the system up and working.
Works just as I hoped it would. Its effective in the first half of the throttle. Runs very similar to a reed motor. The valve dumps the pulse headed up the intake to the carb. This eliminates the over rich condition of fuel reversion and contamination of the air filter. You can feel the pulse exiting the valve.
The idle is much improved, is smoother and will idle at a lower rpm. Tractability is greatly improved. This bike wasn't very happy below 12mph. Now it will ease along peacefully at 6/8 mph.
Throttle response is better from down low as its not over rich from excess fuel.
Probably the only effect it will have on the top end is maybe a bit better running as the air filter should stay less gas saturated. I have cleaned the filter and carb throat area to see if oil accumulates there again.
If you look at the pics of the tube and valve you will see the red tint of the oil that has exited, the gas has evaporated. I will eventually run a very small catch can.
So far Im pleased!
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  #13  
Old 03-05-2015, 10:37 PM
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maniac57 maniac57 is offline
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Talking Re: Modded Boost Bottle

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Originally Posted by cannonball2 View Post
Ok finally got the check valve from the snow bound north. Had already modded the intake so it only took a bout 10min to get the system up and working.
Works just as I hoped it would. Its effective in the first half of the throttle. Runs very similar to a reed motor. The valve dumps the pulse headed up the intake to the carb. This eliminates the over rich condition of fuel reversion and contamination of the air filter. You can feel the pulse exiting the valve.
The idle is much improved, is smoother and will idle at a lower rpm. Tractability is greatly improved. This bike wasn't very happy below 12mph. Now it will ease along peacefully at 6/8 mph.
Throttle response is better from down low as its not over rich from excess fuel.
Probably the only effect it will have on the top end is maybe a bit better running as the air filter should stay less gas saturated. I have cleaned the filter and carb throat area to see if oil accumulates there again.
If you look at the pics of the tube and valve you will see the red tint of the oil that has exited, the gas has evaporated. I will eventually run a very small catch can.
So far Im pleased!
So you notice a change? Very interesting. I basically tuned out at "boost bottle" and had no idea you intended to do this.
I would never have imagined it doing much.
Learn something here every day.
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  #14  
Old 03-06-2015, 08:46 AM
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cannonball2 cannonball2 is offline
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Default Re: Modded Boost Bottle

Most definitely a change. I guess the title was misleading. I was thinking of using the boost bottle but venting it to the atmosphere and using it as a catch can. The idea behind this thinking was to dump the out going pulse, (half the phase of a boost bottle). This returns nothing, which I feel is better for low end. Also there is no need to worry about bottle displacement. I rode the bike a bit after the above post and feel its ride ability is greatly improved over a broader range than I first thought. If I poked around riding slow(trail riding), or idled awhile then the engine had to clear of accumulated fuel, which took several seconds before it would run clean. Now its basically immediate. This means the acceleration is better from the bottom until it tops. No more power or top speed, just smoother operation.
I don't know if this is the "big deal" for all engines. Mine is basically stock, cant say about a highly tuned engine. Someone give it a try. I suspect like a lot of other mods it will have little or no effect on a poorly tuned/jetted engine. But I bet if one has spent a lot of time setting up and jetting an engine and its running pretty well this will add improvement. I will do it to all my engines.

Heres all one needs: A tapped intake with a nipple(mine is tapped midway), a check valve, needs to be Vynar which is fuel/oil proof and a short length of tube to connect it together. I used 1/4" which seems fine, wouldn't go smaller.

Last edited by cannonball2; 03-06-2015 at 08:52 AM.
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  #15  
Old 03-06-2015, 09:17 AM
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Davezilla Davezilla is offline
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Default Re: Modded Boost Bottle

So basically yours is more of a dump valve so the return pulse just goes out instead of being stored and re entered... Good thinking there and if you could use a larger line and check valve it would probably increase low speed rideability even more. I'm thinking you could probably use an automotive exhaust check valve found on some models for pulling in fresh air to feed the catayletic converters or to pull a vacuum off the valve covers as a crank case ventilation system, these check valves are usually 5/8" to 3/4" at the openings and with the right adapter you could run up to a 3/8" or even 1/2"tube off your intake into the larger check valve that could be located under the engine out of sight, or behind the seat post tube out of the way. You would have to weld a tube to your intake manifold's underside that's as large as possible and angle it so the reverse pulse would go into the check valve tube instead of back to the carb, then at the other side of the check valve you could fab up a catch can to catch any fuel/oil that may accumulate.
I doubt it would add any power anywhere, but it would smooth out the lower rpm range and maybe offer up a small amount of part throttle torque once the carb is tuned for this mod. From what you're doing, this mod seems like it would want the largest diameter tube possible at the intake and to the check valve which would also need to be as close to the intake as possible to prevent top end loss, but if done right, at high rpm, the engine would never know that system was in place.
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  #16  
Old 03-06-2015, 11:35 AM
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cannonball2 cannonball2 is offline
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Default Re: Modded Boost Bottle

I agree bigger is better-lol. The little 1/4 was an easy way to test proof of concept and made enough of a difference to think maybe a 3/8-1/2 might be adequate. The advantage to the valves you are referring to is the diaphragm size would probably be more sensitive. The little valves opening pressure is .5lb/in/sq.
This idea was more of a mechanical approach than the concept of intake resonance. Just basically get rid of the excess fuel, a product of the untuned resonance.
I felt the middle of the common upswept steel intake was the proper place to intercept the pulse. Seemed to have guessed right. I noticed many of the CNCed intakes have the port right at the head. I think port placement has some effect.
Just this small valve has made enough of a noticeable difference to make the idea worthy of further development. I may go a bit larger, but will probably leave it to others to run with it.

Have fun!
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  #17  
Old 03-06-2015, 10:13 PM
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Davezilla Davezilla is offline
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Default Re: Modded Boost Bottle

Placement and the angle which the reversion is going into the check valve will both affect the way it dumps off the reverse pulse, if you can fab up an intake with the reversion port at a really tight angle to the intake tract it'll be more effective, pretty much as close to parallel as possible and at least 1/2 the intake tube diameter. the more sensative the check valve the better as well since at part throttle this opening would be the path of least resistance and at full throttle and at low rpm the carb will become the path of least resistance, but if the tube is big enough it can bleed off a considerable amount of the reverse pulse if the hole is on a straight run before a bend headed toward the carb. this could be easily fabbed up on a steel intake that can be welded on, but easier to cut and work if made out of aluminum, either sand cast using another intake as the model for a mold, or just getting an aluminum intake and using some alumaloy brazing rods to braze in the dump tube outlet.
Just a little more fuel for thought... My business has picked up at the shop exponentially in the last 3 weeks so I don't have the experimenting time I had just a month ago but I know you can get it sorted out and working.
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  #18  
Old 03-07-2015, 08:37 AM
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cannonball2 cannonball2 is offline
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Default Re: Modded Boost Bottle

That's why I used the steel angled intake you can silver solder to it. I can only visualize flow and that's not always what happens hence smoke chambers and such. I may have done better with the nipple closer to the bottom, but felt by the midpoint the flow had attached itself to the lower tube wall where the outlet would be right in the flow. Certainly a bigger outlet would be better, looks like 1/2" is probably max before having to fab an intake. Im thinking an outlet at the beginning of the upsweep and parallel to the carbs mounting tube. This is a straight shot right out of the intake port.. Its a simple matter to cut tubing to fit at an angle and solder it there. The angle created there will make a very large opening in the intake. However it may affect intake flow creating turbulence and such or maybe that helps atomize, who knows?

Last edited by cannonball2; 03-07-2015 at 08:41 AM.
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  #19  
Old 03-07-2015, 10:21 AM
KCvale KCvale is offline
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Default Re: Modded Boost Bottle

Spiffy.
Certainly cheaper than an intake reed.

Maybe not so useful on a long offset Z intake as they tend to tame the back pulse, but neat for stock short intakes.
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  #20  
Old 03-08-2015, 03:31 AM
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Default Re: Modded Boost Bottle

That bend right before the carb might be the best place on the top of the intake because the reverse pulse would go straight into the check valve if using one of those stock intakes that have the bend to keep the carb level, it may even be possible to use a smaller diameter nipple in that location and still be effective...
pretty much at any bend before the carb would work so it could even be effective on those longer Z intakes since the reverse pulse would want to go in a straight line more than it would want to make that turn toward the carb.
I'm not a fan of the boost bottle hype but I can see where this would make part throttle performance and rideability more pleasant, maybe even some better part throttle torque or responsiveness could be gained once refined.
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