• Required reading for all forum users!!!

    Welcome!
    Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.

    A note to new registrants...
    All new forum registrations must be activated via email before you have full access to the forum.

    A Special Note about Email accounts!
    DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.

    A note to old forum members...
    I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.

    Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.

    Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...

  • Returning Visitors

    If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.

    If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.

here i go again!!

  • Thread starter Thread starter nert
  • Start date Start date
Not so! From Motorcycle Carburetor Theory 101 www.motocross.com
?The air that is speeding up will cause atmospheric pressure to drop inside the carburetor. The faster the air moves, the lower the pressure inside the carburetor. By placing tubes inside the venturi, we can cause this lower pressure to put fuel into the air stream.?
So your theory is based on incorrect assumptions.
 
"quiet bone-stock Harleys" WHAT a SHAME!!! (where they running?)Thats one of their few endering qualities. hahaha. I love that sound. Often imitated, never duplicated. Really, I do like Harleys. Just too many of them.

The fuel is NOT pulled into the carburetor. It is pushed. The higher pressure in the fuel bowl pushes the fuel in to the lower pressure of the carburetor throat. FACT!

The reason fluid goes up a straw when drinking, is because the pressure in the bottle is greater than the pressure in the straw. basic science. Just like water seeks its own level, pressure seeks to equalize.
 
The reason fluid goes up a straw is because a force is acting upon it to move it. There is greater pressure inside the bottle of fluid than there is in the atmosphere, but a soda pop won't start spraying into the air the minute you put a straw in the bottle. Someone has to suck on the straw to create the negative pressure - or "pull" the fluid up against gravity.


Pushing a fluid involves pressurizing the source - like a municiple water tank forcing the water through the end of your water hose.

Fuel in the bottom of your float bowl does nothing on its own but sit there.
 
I am sorry, science says you are incorrect. There is not greater pressure in the bottle than there is in the atmosphere either as you stat!!!

yes, you create a negative pressure by sucking on the straw, BUT it is the positive/greater atmospheric pressure that pushes the fluid up the straw.

If you blow gently into the straw (not enough to make bubbles) but to increase the air pressure in the straw side you raise the level of fluid in the bottle. Are you going to claim the atmoshere is sucking the fluid up???

If you sucked on the bottle completly enclosed in your mouth, You can't pull the fluid level up. You must have a greater pressure on the opposite side of the low pressure to push the fluid!! Ever shotgun a can of beer???

Thats the way it is!! ITs not my theory. ITs science, Its a fact. Believe it!!
 
As velocity increases, pressure decreases. However, intake volume required is controlled by displacement and rpm. Air volume is a variable. Velocity/vacuum is not. It is controlled. That is the point of a CV carb. At low rpm the engine is circulating a small volume of air. Consequently, the slides are in the lowered position and the cross sectional/throughflow area is restricted, hence velocityvacuum will be at value "X". As rpm increases, required air volume increases, and the slides are raised which provides a larger throughflow area, hence vacuum remains the same at "X". Fuel is drawn through the jets due to a pressure differential. It rises into the carb throat. Therefore, there must be a vacuum in the carb. The float bowls are at atomspheric pressure. Any fluid will follow the path of least resistance. In this case, it flows towards the negative pressure area.
Fuel is not being pushed. It is being siphoned.

Earl


nert said:
Not so! From Motorcycle Carburetor Theory 101 www.motocross.com
?The air that is speeding up will cause atmospheric pressure to drop inside the carburetor. The faster the air moves, the lower the pressure inside the carburetor. By placing tubes inside the venturi, we can cause this lower pressure to put fuel into the air stream.?
So your theory is based on incorrect assumptions.
Click to expand...
 
which is all of what i have been saying. the velocity through the carburetor creates a negative pressure. call it a siphon if you like, but as you said "In this case, it flows towards the negative pressure area."

actually siphon has to do with moving liquid from a container through a "n" shaped tube. moving the liquid up first than down to a lower second container. Different principles apply.

The greater atmospheric pressure IS pushing the fuel. Just like a U tube manometer. If you apply a negative pressure to one leg of the tube, (not enough to siphon) the fluid will rise to the low pressure side due to the greater atmospheric pressure on the other leg of the tube.

anyway, so much for air box leaks.
 
No, it is not a different principle. Fluid moves due to a pressure differential.
You may create a flow in any number of ways, but the principle by which a fluid flows is a constant. there MUST be a pressure differential.

Earl


nert said:
actually siphon has to do with moving liquid from a container through a "n" shaped tube and moving it down to a lower second container. Different principles apply.
Click to expand...
 
differant

Britannica: "The action [of a siphon] depends upon the influence of gravity (not, as sometimes thought, on the difference in atmospheric pressure--a siphon will work in a vacuum) and upon the cohesive forces that prevent the columns of liquid in the legs of the siphon from breaking under their own weight."
 
I have to give you a "NOPE" on that one too. The airbox is restricted so as to match engine intake air volume with jet size to yield an efficient fuel air mixture. Engine efficiency curves reach a point where fuel consumption outweighs HP gains. It is sound engineering to calibrate the induction, exhaust and fuel metering system so as to provide the best fuel economy and the greatest HP. These two are in opposition. The result is a compromise. Noise level and exhaust emissions are also a consideration.
Not sealing the airbox will/can result in the engine running lean if jetting is not changed. Some motorcycles wil run (although not well) with the airbox removed and no jetting changes. The GS's will barely run at all if you remove the airbox and do not rejet. Removing the airbox and rejetting will not noticably increase performance, but it will decrease gas milage. To increase performance, intake, exhaust and fuel delivery must be taken in to account. The whole system must be balanced. For example, discarding the airbox, installing Pods, rejetting and adding a less restricted 4 into 1 header will increase HP. It will also ALWAYS decrease fuel efficiency. In short, you are just reversing the engineering compromise of the manufacturer. Pods, jets and a 4 into 1 may add 7-10 hp to a 750cc size machine, but they will decrease gas milage by 10 mpg. 10 hp on a 750 lb gross weight machine will yield a minimal increase in acceleration for a loss of 25% in gas milage. That is not a good trade off for the normal cruising recreational rider. Keep the airbox and seal it as it should be.

Earl


nert said:
anyway, so much for air box leaks.
Click to expand...
 
:-) What is it you think gravity causes? IT IS A DIFFERENTIAL. The weight of the receeding water in the tube causes the differential. How do you initiate the siphoning process? Maybe by sucking on the lower end of the tube? Since air and water are both fluids, there is no difference in principle between the mechanics of sucking on the tube with your mouth and the following weight of water creating the effect. Agreed, gravity results in weight. Agreed, you can have gravity/weight and a vacuum at the same time.

You cannot have a bucket of water filled to the same level and placed on each side of a 3 foot high wall and expect to siphon fluid from one, over the wall and into the other. Gravity is the same on both sides of the wall. Siphoning will only take place when the fluids are not in equilibrium. Therefore, whether it is gravity induced or mechanically induced, there must be an imbalance to start, and continue the flow. As I said, there MUST be a differential. Britannica is correct............as far as they go.
The principle their observation works by is called differential.

I think you are confusing atomspheric pressure with pressure differential. You may have a pressure differential in the absence of an atomsphere.

Earl


nert said:
differant

Britannica: "The action [of a siphon] depends upon the influence of gravity (not, as sometimes thought, on the difference in atmospheric pressure--a siphon will work in a vacuum) and upon the cohesive forces that prevent the columns of liquid in the legs of the siphon from breaking under their own weight."
Click to expand...
 
air box

air box

Your dead right Earl, but heck let nert take his airbox of and prove it to him self, valves aren,t that expensive, things are a compromise for a good bike, and abike that makes it in the sound department, is nice to the ear, my blke is at about 89db, pull the air box off and it will jump to about, 93db at mid throttle, epa stamp on mufflers say bike stock EPA noise limit should be 87db
 
Re: air box

Re: air box

Yep, I can carry on a normal conversation while standing beside my running 1150. I like it that way. :-) Its quiet and its not all that slow either. :-)

Earl


Gee-s-is said:
Your dead right Earl, but heck let nert take his airbox of and prove it to him self, valves aren,t that expensive, things are a compromise for a good bike, and abike that makes it in the sound department, is nice to the ear, my blke is at about 89db, pull the air box off and it will jump to about, 93db at mid throttle, epa stamp on mufflers say bike stock EPA noise limit should be 87db
Click to expand...
 
My intention was NOT horsepower, nor was it "sound". I have not yet heard a reasonable answer as to why some claim their engines won't even idle if they have an air box leak. I guess if you can deny science and the facts, and britanica definitions, you can justify your claims.

I guess i will take a nice long ride on my GS into the sunset....unless of course you believe i will fall off the end of the earth. :lol:
 
I guess i will take a nice long ride on my GS into the sunset....unless of course you believe i will fall off the end of the earth.
Click to expand...

:lol: :lol: :lol:

I can say by experience that my bike idles just fine without the air box or filter installed. I don't understand that either Nert.
 
Nert - you've got waaaaay too much time on your hands. There have been plenty of explanations as to why air box leaks can cause your bike to run poorly, but we've gotten caught up in the symantics of carburetion.


nert said:
I am sorry, science says you are incorrect. There is not greater pressure in the bottle than there is in the atmosphere either as you stat!!!
Click to expand...


But there is greater pressure in the pop bottle - that's what the bottle is for. Take into account the weight of the liquid pushing on the walls of the bottle. The liquid wants to find its point of equilibrium with gravity, but the bottle prevents that - so the liquid pushes on the walls of the bottle and the bottle pushes back until they achieve stasis. Don't forget about the effect of gravity and mass on pressure.

Defining siphoning as only working through an "n" shaped tube is simple naivite - that example is only for gravity siphoning. There is mechanical siphoning as well, examples being bilge pumps, windmills, and carburetors.


The difference between pushing and pulling fluids is thus:


A distillery pushes fluid by creating a pressure differential through the use of heat. All things being at a stasis, mass will not move without application of energy. In this example, the energy is being applied at the source of the liquid (heat) to move the liquid to the other end of the still. Heat increases pressure at one end, pushing the liquid to the area of lower pressure at the other end.

A siphon or (vacuum pump)does just the opposite. Energy is applied at the destination instead of the source, creating an area of lower pressure which pulls the liquid to its destination.

It's all about where the energy is applied to the apparatus - you pull a shopping cart from the front, or push it from the rear. While you're touting scientific constants (none of which are being argued here, I assure you), don't forget about the fine points of the English language.


And finally, I'll leave you with the scientific evidence you crave.....


Google "Stoichiometric Ratio".



-Q!
 
nert said:
My intention was NOT horsepower, nor was it "sound". I have not yet heard a reasonable answer as to why some claim their engines won't even idle if they have an air box leak. I guess if you can deny science and the facts, and britanica definitions, you can justify your claims.

I guess i will take a nice long ride on my GS into the sunset....unless of course you believe i will fall off the end of the earth. :lol:
Click to expand...



A bike whose mixture is already lean (as these bikes all were from the factory for emissions reasons) will idle poorly (if at all) with no airbox.


Mine, on the other hand, runs well with no air filter because it's jetted too richly.
 
It isnt a claim. I dont need an encyclopedia to tell me that a lean running engine can burn valves. :-)

Hope you enjoy your walk back. :-)

Earl

nert said:
I guess if you can deny science and the facts, and britanica definitions, you can justify your claims.

I guess i will take a nice long ride on my GS into the sunset....unless of course you believe i will fall off the end of the earth. :lol:
Click to expand...
 
Jethro said:
Glad I got outta this one early!
Click to expand...
Glad I never got into it, period!! :)
I can simplify things:
CV carbs run bad with air box leaks.
VM carbs run OK, but leaner.
 
You must log in or register to reply here.
Back
Top