Custom Velocity stack

So here's a velocity stack i just fabricated.. comments?

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Re: Custom Velocity stack

second pic

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third.

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Re: Custom Velocity stack

Looks good, can you figure out a way to smooth the transition from the stack to the intake?

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The pipe fits directly on the carb (bing), i'll just have to shorten it a little bit and have a clamp tighten it.

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Is there a ridge from the cone to the straight section? Might mess things up a bit, try to smooth that out and you'll be good :)

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Looks like the nozzle for a saturn 10 rocket

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Bruce Edwards /

OK, since no one else either knows what a velocity stack is or is willing to say it, I will. The curve of your bell is the exact opposite of what it's supposed to be. It's totally wrong and useless. Worse yet, it will most likely inhibit performance.

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That is one ranky ass looking toothbrush.

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yes satoch.. after building it, i did further research on velocity stacks and realized what i had built was far from one and useless, i wont be installing it considering there is absolutely no point, but it was well worth trying to do something for my moped with random trash laying around, trying things out of the common can also benefit and work.

Re: Custom Velocity stack

(wiki'd and copied in less than 5 seconds.)

sorry friend, but HOW was it "well worth trying" when you "won't be installing it considering there is absolutely no point" ?!?

someone trying something uncommon would be nice to see. but don't you like your bike enough to NOT go experimenting with "random trash" and zero knowledge?

why did you want us all to see this?!?

you did not "fabricate" it!!! you found a few pieces that fit together and attached them with some glue.

mot a dit..

please try harder next time. we'll be here!

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rough...

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So I haven't really seen it discussed, but with a velocity stack are you essentially running no air filter?

Or is there a thin filter inbetween the stack and the carb body?

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to northernmike... what makes you think ive got no knowledge? not because youve been on this planet for ten more years that your any fucking smarter..

and i dont know if its just me but the tone youre using seems the tone of a square head trying to insult a French frog.. well listen bro.. i might be french but im not ignorant enough not to learn your fucking language..

p.s. Nice shirt you got in profiles pic.. did it come with a dick in your mouth?

Re: Custom Velocity stack

Francois. I like french people. I have a french bike. I'm dating a girl from Quebec. I like young people, a lot of them are smart, and a lot of them smarter than me.

Maybe I was a little hard on you there. I'm sorry about that. Let me explain a little about how I use these forums and why your post disappointed me so badly. I'm not saying I am justified in being as harsh as I was, but look at it my way for a minute.

First and foremost, this board is populated by a lot of people who have built some very fast bikes. There are people here who have created bikes that do 50 and 60mph. I have not done that yet. I've been asking questions, discussing with people here, using the search function and the rest of the internet (like wikipedia), talking to tuners of 2-stroke motors in the real world and as such preparing myself to make intelligent, informed decisions on what to do with my motor.

If I create a thread here in "Performance Tuning", my intention is either to share knowledge or gain knowledge. Were I interested in creating a velocity stack, for instance, I would know that there is some serious math involved and the basic principles behind it - because I've had a cursory skim through Gordon Jennings' Two Stroke Tuners Handbook, which everyone who asks humbly enough here is instructed to read.

A most basic, even instinctual understanding of fluid dynamics should have told you that the 'rocket launcher from the trash' design would be of no value.

I, unwittingly, assumed that a thread entitled "Custom Velocity Stack" would be showcasing someone's hours of math and lathe work, and possibly a comment on the creation's effect on performance. My mistake?

But maybe there's hope for you. Do some reading, ask some questions, visit a small engine shop, do things that smart bilingual kids do when they want a fast moped. Like I said, we'll be here!

If you continue to try to make parts out of junk to do things that you don't understand, you'll continue to fail.

I think my shirt looks a lot better than your velocity stack.

SO. Go read Jennings, use the forum search, check out some french mob tuning websites, the mob turcs, wiki, and make that squarehead bike of yours a moby-killer.

Allez!

Re: Custom Velocity stack

Bruce Edwards /

Slocketman, most of the time a velocity stack is used in pure racing applications and no filter is needed.

However, some stacks do have filters. I've seen them for Harleys. I will be designing and testing a filtered moped

stack/carb venturi/intake on a flow bench in the future.

I will be using this research:

DUAL SOLUTIONS FOR STEADY LAMINAR FLOW THROUGH A CURVED TUBE

S. C. R. DENNIS and MICHAEL NG

( Department of Applied Mathematics, University of Western Ontario London, Ontario, Canada )

Numerical solutions of the Navier-Stokes equations are presented for steady laminar flow through a slightly curved tube of constant circular cross-section. The motion is due to the action of a constant axial pressure gradient and depends upon a similarity parameter which is designated the Dean number D. The solutions are obtained by a method in which the basic two-dimensional partial differential equations governing the motion are reduced to infinite sets of ordinary differential equations for the dependent variables using substitutions of Fourier series. The infinite sets of equations are then reduced to finite sets by truncating the series and the finite sets are solved numerically to give an approximation to the flow. The solutions cover the range D = 96 to 5000. For D<956 only one solution can be found for a given value of D. The secondary flow consists of a symmetrical pair of counter-rotating vortices of Taylor-Goertler type. The same type of solution can be found for D>956, but in addition a second family of solutions can be obtained in this case in which the secondary flow has a four-vortex pattern consisting of two symmetrical vortex pairs. The properties of the two-vortex family of solutions agree well with those of previous calculations; the four-vortex solutions have not previously been obtained for a tube of circular cross-section

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but, satoch - those equations are for "steady laminar flow through a slightly curved tube of constant circular cross-section".

does the charge not fog IN AND OUT of the carb in 2-stroke applications? that would not be steady laminar flow.

how do you calculate the curve and length of the stack with this?

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Bruce Edwards /

I'll have to look into it further. I'm guessing that some calculations combined with a flow bench and good old fashioned "trial and error" testing will provide the quickest positive results.

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I've got two bing V-stack done, one tested and proven. Watch for a post in the near future with details and build instructions.

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yamaha R6 - "variable length intake trumpets" - electronically adjust depending on rpm.

and with that, i've resumed drinking.

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rather

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HAH. francois wins, hands down.

(allons enfants de la patrie . . . le jour de gloire c'est arrive!)

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he won? what did he win?

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Bruce Edwards /

You win! I'm working on a similar idea for a variable tuned length exhaust for the Tomos A55 engines by using servos and an RPM sensor.

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