Boost Bottle Dyno

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Smoker
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Boost Bottle Dyno

#1 Post by Smoker » Mon Dec 24, 2018 1:33 pm

Trying hard to search and learn some tidbits about building 2-stroke engines.

Finding it somewhat difficult to get helpful info. :smt003

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brrrappp
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Re: Boost Bottle Dyno

#2 Post by brrrappp » Mon Dec 24, 2018 1:58 pm

I would start with the Two-Stroke Tuner's Handbook by Gordon Jennings.
http://edj.net/2stroke/jennings/

This is not specific to RZ350/500 it's more general 2-stroke guideline.

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Re: Boost Bottle Dyno

#3 Post by Questo vecchio rz » Mon Dec 24, 2018 2:43 pm

Don't know bout you...Pete ,but think I'd like the turquoise line. You could only imagine what accolades the text would say!!!
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Re: Boost Bottle Dyno

#4 Post by T.RexRacing » Tue Dec 25, 2018 1:09 pm

Harry Barlow did a lot of dyno testing developing a boost bottle for the RZ engine. He's a tough guy to pin down solid information on though. There's an SAE paper on the Yamaha YEIS by Noriyuki Hata and a couple others as well. I have a Barlow bottle I got from Supertune Chuck that worked well but never did any dyno testing to verify.

EDIT:I found a paper by Chinoy on his work with boost bottles. Lemme know if ya want a PDF of it.

Here is a site that covers them well using the Yamaha paper extensively.
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Whymee
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Re: Boost Bottle Dyno

#5 Post by Whymee » Tue Dec 25, 2018 10:38 pm

Thanks for the link. Interesting read!
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Re: Boost Bottle Dyno

#6 Post by RuZty » Wed Dec 26, 2018 10:40 am

I read the Yamaha SAE paper about 15+ years ago and made up a spreadsheet to work all the numbers. I made a couple of variations of bottle diameter and hose length, one each side connected in place of the crossover tube. It made a small but noticeable difference, and the changes I made had the intended effect, but I never dyno'ed it for comparison. Note that when 'engine size' is referenced in the article above it means individual cylinder size. I only used individual bottles on each side because I couldn't find any information on how the math related to a container with 2 outlets, like the ones commonly sold for Banshees that sit across the top of the manifolds. That size bottle would require a far longer connecting pipe if it were applied to one cylinder. For whatever reason (winter, new kid, boredom) I never went back to this, but for perspective the changes it made to performance and rideability were a fraction of what was achieved by switching to Keihin PWK 28's.

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Re: Boost Bottle Dyno

#7 Post by brrrappp » Wed Dec 26, 2018 3:43 pm

RuZty wrote: Wed Dec 26, 2018 10:40 am I read the Yamaha SAE paper about 15+ years ago and made up a spreadsheet to work all the numbers. I made a couple of variations of bottle diameter and hose length, one each side connected in place of the crossover tube. It made a small but noticeable difference, and the changes I made had the intended effect.... but for perspective the changes it made to performance and rideability were a fraction of what was achieved by switching to Keihin PWK 28's.
Agree!
Do you run the crossover tube with your PWK 28's ???
I am curious as to any effect you may have noticed with and without the intake crossover connection. Was it good, better, and best? Or was it Crap, good and better? :smt003

I always felt the YEIS (boost bottle) was more show than go. That Yamaha did not install YEIS boost bottles on every 2-stroke made going forward from the mid 80's through the current 2-stoke YZ's says something about the need or effect. It's a low-tech/inexpensive item that could easily be part of production and yet we haven't seen them be widely used in years.

The simple crossover tube on a twin cylinder is likely more valuable to performance than the boost-bottle. Crossover tubes or modulated gateways between intakes were also used to good effect in 4-strokes. Most notably the V-Max motorcycle where it was called v-boost.

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Re: Boost Bottle Dyno

#8 Post by JonW » Wed Dec 26, 2018 6:15 pm

Interestingly I was chatting to a racer a while back and he suggested to me that fitting the RZ crossover and manifolds to the LC was a 'trick' they did. I was taken back, how would using a tube with a bit bigger diameter make any difference at all?! But then of course Yamaha did it for the RZ... so.... Anyone else done this and found any noticeable improvement?
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Re: Boost Bottle Dyno

#9 Post by RuZty » Thu Dec 27, 2018 5:12 pm

brrrappp wrote: Wed Dec 26, 2018 3:43 pm
Do you run the crossover tube with your PWK 28's ???
I am curious as to any effect you may have noticed with and without the intake crossover connection. Was it good, better, and best? Or was it Crap, good and better? :smt003
I've always used the crossover tube, except when the boost bottles were connected in their place, as much because removing it would mean plugging the holes. Maybe I'll give it a try in the spring and see what the difference is. Never tried the boost bottles with the PWK's.

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Re: Boost Bottle Dyno

#10 Post by JonW » Thu Dec 27, 2018 7:16 pm

A local guy swears he got a much faster engine by taking off the x-over and plugging the holes. i didnt really believe him but he was adamant it was the best thing he did etc
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Re: Boost Bottle Dyno

#11 Post by T.RexRacing » Fri Dec 28, 2018 12:50 pm

I tried that and found an off idle stumble I couldn't tune out w/30MM VMs.

While Barlow found a power increase w/boost bottle most of what I felt was an increase in driveability. That soft area 3-5K RPM where the stumble shows up sans airbox was much cleaner and a smooth transition into the powerband evident. Just like a good advance curve and careful jetting it's another contributor to a good rideable tune. To me it's the difference between "it runs" and "it rips."
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Re: Boost Bottle Dyno

#12 Post by brrrappp » Fri Dec 28, 2018 1:33 pm

That would make sense since the boost bottle, like the crossover tube, was supposed to keep the airflow smooth at low-mid RPM. It acts as a buffer to the stop/start/stop/start airflow as the reeds snap shut and reopen. I would doubt any claim of HP gains at the mid to upper end since the pulses are too fast to be noticeably affected by the boost bottle.

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Re: Boost Bottle Dyno

#13 Post by T.RexRacing » Fri Dec 28, 2018 4:47 pm

If it pulls cleaner it will measure higher output across the board. Remember time is part of the equation to calculate horsepower. TorqueXRPM/5252=HP. Revolutions per Minute. Top fuel crankshafts rotate about 600 times in a 4 second run and are estimated in excess of 10 thousand HP.
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Re: Boost Bottle Dyno

#14 Post by brrrappp » Fri Dec 28, 2018 9:03 pm

T.RexRacing wrote: Fri Dec 28, 2018 4:47 pm If it pulls cleaner it will measure higher output across the board. Remember time is part of the equation to calculate horsepower. TorqueXRPM/5252=HP. Revolutions per Minute. Top fuel crankshafts rotate about 600 times in a 4 second run and are estimated in excess of 10 thousand HP.
That's not exactly true.

RPM is simply a point on the graph where a Torque measurement is taken.

The element of time in the equation does not ensure an engine that "pulls cleaner" equals an engine that has HP increases across the board. Nor does the fact that a drag race crank turns at incredibly high RPM.
Raising RPM creates more horsepower for a specific measure of torque because the measurement for horsepower = work done in a specific amount of time.
(Torque) A foot-pound is the work it takes to lift 1 pound a distance of 1 foot.
(Horsepower) The rate of work, calculated as the amount of work done divided by the time it took to do it.

The HP equation is a method of converting the MEASURED TORQUE output at a SPECIFIC RPM into a number representing Horse Power (work done) for a SPECIFIC RPM.
As anyone that has worked on internal combustion engines knows, it's quite easy to have an engine sound and pull more cleanly while actually making less top end horsepower. This is especially true of two strokes where expansion chamber design impacts specific RPM ranges.
Last edited by brrrappp on Sat Dec 29, 2018 12:00 am, edited 1 time in total.

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Re: Boost Bottle Dyno

#15 Post by T.RexRacing » Fri Dec 28, 2018 9:58 pm

OK.
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