Motorsports Village
http://motorsportsvillage.com/forum/

Emulsion
http://motorsportsvillage.com/forum/viewtopic.php?f=6&t=7410
Page 1 of 5

Author:  nomad [ Wed Jul 07, 2010 5:11 pm ]
Post subject:  Emulsion

I can look up the answers on this but, I'd like to pose this question for discussion purposes. Hopefully, some of us can learn some more stuff we can apply, or better understand, to what we are trying to do with our Holleys.

Doesn't the Quadra Jet have emulsion tubes in the mainwells? Is this system similar to that of Webers? Is is superior to the Holley configuration?

Further, don't they also just have disharge tubes in the secondaries rather than boosters? How does the fuel atomize without that booster?

It seems to me these carbs run pretty well when prepped by the right person.

Okay, I asked more than one question, don't shoot me.

Author:  Eric68 [ Wed Jul 07, 2010 7:45 pm ]
Post subject:  Re: Emulsion

nomad wrote:
Further, don't they also just have disharge tubes in the secondaries rather than boosters? How does the fuel atomize without that booster?


Don't have all your answers, but on the Q-jet secondary discharge tube -- they work, but not very efficiently. I feel the same way about "aerosol" boosters (aerosol is a code word for repackaged Q-jet technology LOL). They are not very sensitive to airflow and the response was weak when I measured some aerosol boosters on the flow bench.

Author:  shrinker [ Wed Jul 07, 2010 8:35 pm ]
Post subject:  Re: Emulsion

A booster is just a vacuum amplifier. It generates a vacuum that is higher than would be achieved at the center of the main venturi alone. The vacuum can be graphed as a line. it might be a curved line or other shape due to how the air enters the booster and exits it. Booster placement in vertical height in the main venturi affects all that as well, the air flow entrance to the main venturi influences what happens in the booster . A booster is a venturi meter for an airflow.

Emulsion is a correction for incorrect vacuum performance from a booster. It is also a correction for incorrect main jet design. Carburetors can, and are, quite successfully used without emulsion. However the carburetor must be specifically tuned to each engine more accurately if its a no emulsion design. Using a design with no emulsion is not a carby suitable for hotrodders. It takes a high level of machining accuracy and a lot of testing to achieve a desired result without emulsion. It is very easy to alter fuel curves etc with emulsion. Using emulsion is cheap, easy, bulk mass production techniques.

Author:  nomad [ Thu Jul 08, 2010 9:54 am ]
Post subject:  Re: Emulsion

Ya know, I've never seen an aerosol tube discharging at full throttle. Maybe someone has a video of that and can share. I know there seems to be a lot of passionate discussion on a well know piss and moan board about big holes and tubes. But, I'm just looking to increase my knowledge about carbs.

Anyhow, it seems that lots of folks think the Q-jet is a darn good carb if one knows what to do with it. Why is that? Can I apply those lessons to what I'm learning now? Trust me I've learned some lessons recently.

What I was trying to get at: Is emulsifying the fuel in the center of a fuel well superior to the Holley method from the side? Make me think answers mean more to me than the straight out answer.

Author:  shrinker [ Thu Jul 08, 2010 4:21 pm ]
Post subject:  Re: Emulsion

Superior in what way? Consider that air bubbles lower the density, So therefore that lower density fuel 'floats' on top of the normal fuel. that causes the lower density fuel to have a higher surface level than normal density fuel. Once the surface level is up to the height of the outlet tube it can flow to the booster. Thats when the engine starts to run on that fuel. At low air flow levels thats all that happens. Your using air to make the surface of the fuel closer to the outlet. At higher flows through the carby the main jet restriction causes sufficient reduction of the liquid level in the well to fully uncover some bleeds. When its like that the air flow through the bleeds blows the fuel along its path. The amount of blow etc is controlled by the MAB and the sizing of the various E-bleeds. Now also think about what happens when the fuel flow into the bowl causes a lowering of the level. That means the pressure on the entrance to the main jet is changed, so the flow rate of the jet alters and that alters the level of fuel in the well. Now what happens if you change the main jet size? Same thing isnt it.

Ok so now put all the emulsion holes on a tube like the Weber plates. If you make them in the same arrangement as a Holley then it will do very similar things. But because you have a tube you have lots of places to put the E-bleeds, you can place them all at one level if you wish and that allows you to have lots of fine bubbles at one place, you can have lots of air but have it as fine bubbles. If you try to do that with the Holley design you can only have one hole and it has to be big to pass the air and then you only get one bubble of air. You get a different density change if the bubbles are one single one or lots of tiny ones. Lots of tiny ones creates lower density. Big bubbles travel faster though. do a experiment with an aerator on a faucet outlet at the kitchen sink. When your filling a glass with non aerated water the big bubbles float up quickly. When you fill it with an aerator nozzle the tiny small bubbles take longer to float up. BUT small bubbles just alter the density and viscocity, where as big bubbles can form a block of air moving through a tube. So when you have a block of air exiting the booster where is the fuel for that parcel of metered air? What does that cylinder run on then?
So now what do you do with the carby, will a large bottom air bleed get you a big enough droplet to blow fuel faster to the booster at high CFM flows? Will tiny bubbles help it start the mains flow differently at low CFM flows?
So answer this question, Which bubble structure will create more even fuel distribution exiting from the carby base?

Ok so know work out how you would make a droplet flow in a stream of air inside the drillings of the carby. How much air do you need to keep a droplet and not have the fuel as a liquid with air bubbles in it. Think about how to make it air with droplets in it, thats the other way around isnt it. pretty obvious you needs lots and lots of air.
Ok so now how do you get that main jet to start making droplets instead of just passing liquid, how do you get the outlet of the main jet to form a droplet and then keep it as it smashes into the right angle bend trying to turn into the well? (Then go read what Jmarkaudio pointed out that I said on ST)

Now think about how a straight tube like used in the C&S alcohol varieties instead of a booster might discharge, what is going to be coming out of the tube?
Now what happens when you drill out the discharge tube on a booster, does it slow the flow or does it create a greater surface area around the tube internal circumference for the fuel to wick along and allow air to go down the middle?

Very interactive isnt it.

Author:  nomad [ Thu Jul 08, 2010 6:53 pm ]
Post subject:  Re: Emulsion

Thanks shrinker. Your explaination is helping me to understand. it'll take a couple of reads, four or five most likely. I'll print that out and take it with me on the plane tomorrow.

Meanwhile, I'm off to the sink for a glass of water. ;-)

Author:  shrinker [ Thu Jul 08, 2010 7:09 pm ]
Post subject:  Re: Emulsion

Do you want more things to think about?
Figure out what happens to the fuel that's on the inlet side of the E-bleed. When the engine is off that well is full of fuel. When the air pressure forces down on that fuel where does it go? Is that metered by the main jet? Does that give the booster a shot of richer AFR for a short term? Is that like an accelerator pump shot? Was that done on a Ford T carby? Oh Gosh it was. In fact everything that you want to try on a booster carby was done 100 years ago. Its not secret squirrel stuff, there are no special circuits that someone has developed that give more horsepower and torque. IT'S ALL BEEN DONE BEFORE.
Grab yourselves an Automotive encyclopedia from somewhere around 1910 and everything is explained very well in those books. It was all new stuff back then so it was correctly identified and explained. Proper scientists investigated carburation, not like it is now where it's turned into something mysterious by self promoting people who havent a clue about history.

Now think about the volume of fuel on the inside of a Weber emulsion tube.
What happens to your Holley if you machine the air well bigger and increase the fuel volume on that side?
What happens to the fuel in those very low additional circuits in those Braswell blocks? When does it come in to the AFR and what sort of throttle stab will it be effective at?

See its not secret stuff, its school boy physics. There is skill in designing a carby but there is more skill in recognizing what you have to change for the engine. To do that you have to have at least a gas bench to show you the gas constitution of the exhaust and you have to read plugs so that you can see the carbon deposition of the initial kernel and other details. Which reminds me, UNLEADED FUEL TANS A PLUG EXACTLY THE SAME AS LEADED FUELS. I read all the time by so called knowledgeable people that unleaded fuel doesn't color a plug. It's even said that it burns so clean that it leaves no deposits. BAH. Bit off track here but its chemically impossible for a rich mixture to not produce carbon. If the people who claim unleaded doesnt color actually thought about it they would realize that if it didn't color then it must be leaner than stoich to do that. So how come the exhaust pipe is black? Why is there carbon in the pipe but not on the plug? Well it turns out that the mixture on the plug cant be the same as the rest of the cylinder. Why is that so? --- Because its not vaporized enough at the plug. Why? Because its not atomized enough. WHY? Because the carbys havent changed design since 1926 when the first emulsion design carby was born. But lets keep it all a secret shall we.

Author:  jmarkaudio [ Thu Jul 08, 2010 8:55 pm ]
Post subject:  Re: Emulsion

nomad wrote:
Thanks shrinker. Your explaination is helping me to understand. it'll take a couple of reads, four or five most likely. I'll print that out and take it with me on the plane tomorrow.

Meanwhile, I'm off to the sink for a glass of water. ;-)

Take two aspirin and call...... ;-) A lot to swallow in one sitting. :-k

Author:  jmarkaudio [ Thu Jul 08, 2010 11:26 pm ]
Post subject:  Re: Emulsion

Eric68 wrote:
nomad wrote:
Further, don't they also just have disharge tubes in the secondaries rather than boosters? How does the fuel atomize without that booster?


Don't have all your answers, but on the Q-jet secondary discharge tube -- they work, but not very efficiently. I feel the same way about "aerosol" boosters (aerosol is a code word for repackaged Q-jet technology LOL). They are not very sensitive to airflow and the response was weak when I measured some aerosol boosters on the flow bench.



Actually I don't think the Quadrajet has the same issues to deal with that the C&S carb has. The secondaries have an air valve above the discharge tubes that helps maintain a stronger signal to the discharge tubes.

Author:  gregory [ Fri Jul 09, 2010 6:40 am ]
Post subject:  Re: Emulsion

Something to think about here.
I believe that one of the most important factors about carburettors and combustion efficiency is the ability to obtain, (as close as one can)…smooth, normal combustion completeness.
Now, a vital part of this being accomplished is the ability to obtain high levels of air saturation, beginning the very moment the engine is running.
Very good levels of air saturation are the key to obtaining good amounts of fuel gassing in the intake tract.Gassing in the intake tract is very important to achieving the least amount of wet and dry patches in the cylinder prior to ignition time.

The engine runs on the transfer slot fuel first, and its this fuel that saturates the airstream for consistent fuel gassing in the intake tract.
This fuel that comes out of the transfer slot continues to come out quite high in the load settings on some engines and has a profound effect on the amount of combustion completeness that is reached.
To obtain a smooth running set of cylinders you need saturated air going to ALL cylinders.
The transfer fuel can be smaller in droplet size than the fuel that comes out of the main boosters, so it can deliver a different cylinder condition than the booster fuel.
You can choose to have either small droplets or larger blobby fuel drops exiting the transfer slots of a carby,its up to the operating to calibrate the t/slot/ifr/iab so as to achieve well saturated air exiting the carby.
The transfer slot reacts to the vacuum that is under it and the air leak that is on top of it, so all different engine combinations will deliver different amounts and sizes of fuel droplets, and here in lies the saturation level and quality.
Carb sizing plays a huge role in achieving good air saturation out of the transfer slot as well as the camshaft and port sizing.
Very,very little fuel emulsification has taken place at this point, if any at all..

I believe that a very good place to start with tuning a holley,is to experiment yourself with the transfer fuel,and obtain a good understanding on how it effects the combustion make-up and how the molecules convert.To do this you need to use a 5 gas analysis machine to slowly get an understanding on what change that you make effects the combustion.

When you analysis the combustion after or as you change the saturation level exiting the transfer slots,you will see differences in the gasses that exit the cylinders,the way that the engine sounds,smells and emits visible contaminants.You will see different deposit colours,styles and amounts on the plugs and in the exhaust pipes.

When you start to learn like this and realise how the transfer fuel can have such a huge effect on the cylinders,you will get to see some very interesting things indeed.You will see power increases at WOT and at many different rpms other than the idle.this is quite an eye opener and it is for this reason that I say these things.You will begin to understand how a drop of fuel here or there can effect the running of an engine.

Im not trying to take this thread over,but rather point out some findings that I have seen,that will help you with your holley.

Author:  nomad [ Fri Jul 09, 2010 2:11 pm ]
Post subject:  Re: Emulsion

While, I'm still absorbing shrinker's posts on emulsion he brought up another point that affects my car directly. Running on no-lead.

In my journey with carbs I have been running a 93 octane, 110 octane mix. 20% 110 and the rest 93. I have seen that the plugs while not bone white they are at least a dirty ivory color. No color change on the electrode, and the base ring of the threads black. In my last motor, at the same squeeze and the same plug burning a 50-50 mix would show what we all think good color. Yet, the color inside of the headers is the same dark gray in both engines. I have never felt that no lead won't color plugs.

jmark has pointed out that I may be suffering from poor combustion characteristics. I agree and it appears that shrinker has pointed that out. Unless, of course, I am mis-interpreting what I've been reading.

I'm an optimist and I believe i can get this engine running razor sharp with patience help from my fellow posters.

Author:  jmarkaudio [ Fri Jul 09, 2010 2:33 pm ]
Post subject:  Re: Emulsion

It's not necessarily that you have poor combustion characteristics, but that the nature of using lower compression will have an effect. Fuel choice can improve it, the right heat range plug (Your ignition should have plenty spark for it), as well as balancing the carb size and carbs atomization characteristics to get sufficient atomization for your induction and combustion chamber design. You already have the engine you have, short of changing pistons, heads, cam, the best for what you have is to find the best fuel to use and the carb used. We have enough of those to play with. ;-)

Author:  shrinker [ Sun Jul 11, 2010 7:28 am ]
Post subject:  Re: Emulsion

I agree with Mark. please consider thinking about an engine in this way. Do not think of an engine as an Air pump. That is a very inhibiting way to discover or understand the factors in an engine.
I think its better to think of an engine as a machine to raise the energy level of a fuel to as high as possible prior to initiating controlled combustion. That sentence really needs thinking about. If you approach an engine that way it opens a whole new way of thinking about whats going on inside a cylinder.

If you design an air pump engine you can have no regard for what the fuel condition in the cylinder is. You will just concentrate on pumping air. The more air you pump, the better you think it will be. Follow me here, If you inject the fuel via direct injection into the cylinder one degree before the arc discharge across the plug and you inject the fuel in one big blob, then what good is that going to be to you? Will it even burn? If the blob of fuel is over on the other side of the chamber then nothing going to happen is it?
So by now we have realized that the fuel needs to be at least near the sparkplug . Ok so now get rid of that silly injector and use a carby. Now we have air and fuel mixed in a nearly continuous manner inside the carby.Thats what Gregory is talking about. Maybe were just looking at low speed running, the Idle and transfer circuits are doing most of the fueling of the engine, if the fuel comes out from the T-slot in a blob then its going to get caught in a runner and that might over fuel that cylinder. So now think about what happens to a cylinder that gets the dryer bit of air that is in between the blobs? What does that cylinder run on?
See how an engine is not just an air pump, its a machine to distribute fuel and vaporize it and raise its energy level prior to controlled combustion.
If you burn petrol on the ground its not very violent is it. Compress it and its gets violent. Compressing it raises the energy level of the fuel and gets it closer to the self combustion point. That's what you have to do with an engine, raise the energy of the fuel to close to self combustion but not exceed that limit until the arc discharge. You can fiddle with the engine and alter how much energy it puts into a given fuel or you can fiddle with the fuel and adapt it to the engines limitations.
Fuel ignites when the energy level of the fuel molecule and the oxygen molecules is high enough for the oxygen to exchange electrons. That exchange is towards Oxygens favour, oxygen rips the fuel molecule apart if you like, Just think of it as a simple thing, the oxygen is the destroyer of the fuel molecule. The hotter you get the fuel and oxygen the faster the reaction happens. You can react fuel or anything in a long time if you like, you can rust steel slowly at room temperature or you can heat it up with a flame and shove lots of hot oxygen at it and you have an oxy-cutting torch. Its the same basic process one is slow one is fast.
What you want to do in an engine is oxidize the fuel fast. But not too fast, thats detonation and the parts cant handle it. OK so how do you get the oxidation speed to manageable levels, well you compress it just enough but not too much. You all know how too high compression results in detonation. But the opposite is that too low compression doesn't raise the energy level enough.
Now figure out how much compression you get from inlet valve closing to arc discharge time.. And think about how different cams change that.
So when you have a big cam and 10:1 compression you not getting what you think you have. If you don’t actually compress the fuel much you don’t add enough heat to the droplets. If you don’t heat the drops up enough you don’t turn the liquids into a gas. If you don’t turn it into a gas you cant mix it with the air, So you get zones of rich air around a droplet and the leanest air between droplets. That’s what happens in reality, Any time a few molecules are attached then you still have a liquid and it still acts as a liquid. You have to heat the liquid to a gas before it will burn. This basic concept is known by many people, but the implications of it are not appreciated by many people.

So when you have a rich mixture as an overall measurement of a cylinder you should get carbon deposits or very high levels of carbon gases. When you don’t get any carbon on the plug then the environment around the plug must be stoich or close to it or leaner than stoich. So ask this question, If I have a rich overall cylinder then how come I’m getting a leaner burn around the plug? It means its not gassed enough by the compression process. Now what happens next is the kicker, If its not gassed enough around the plug, then its also likely that its not gassed enough elsewhere in the chamber (the plug is pretty hot isn’t it, so the rest of the chamber is probably colder). So now the heat from the lean burn is used to gas the liquids in the rest of the chamber and that means your using energy that should be pushing on the piston to boil some liquids instead. And your doing the boiling first then the burning later in the stroke or later in the process so your not going to get those fuel molecules to burn in the nice tight TDC environment. What does that mean to the energy release of those fuel molecules? Its not as good is it. So your power is down. Bugger.

Author:  jmarkaudio [ Sun Jul 11, 2010 10:17 am ]
Post subject:  Re: Emulsion

In Bruce's csse, I think the right fuel selection will help. While he is playing with different tunes, we do have a "Tuner" setup on the Dominators that leans the transition with restrictors and ups the IAB's for both idle and transition to get them lean enough. And he runs a transbrake, never under a real load until at least 4000 and running WOT all the way down.

As far as tube emulsion, it would appear the right combination of smaller holes in the right location will promote a more even supply of fuel to the booster, but will the lack of velocity in the mainwell or the lack of fuel in an emulsion well be a hinderance?

Author:  shrinker [ Sun Jul 11, 2010 5:28 pm ]
Post subject:  Re: Emulsion

jmarkaudio wrote:
as far as tube emulsion, it would appear the right combination of smaller holes in the right location will promote a more even supply of fuel to the booster, but will the lack of velocity in the mainwell or the lack of fuel in an emulsion well be a hinderance?

Velocity in the main well, that's interesting. The velocity of a fluid traveling in a conduit can be reduced to a dimensionless number called Reynolds number. There are explanations of it on the net everywhere but what it basically is is a number that you arrive at by applying a simple formula and that numbers value is how you can determine what type of flow condition the fluid is in. You have 2 basic types of flow, Laminar and Turbulent. There is an additional flow or transitional, that's half way between the 2 states. There is another thread on here somewhere where I talked about that in more detail to Mark who does the E85 stuff.
Anyway with Gasoline or Methanol the flow becomes turbulent at quite low power levels. I think I detailed how to work that out in the other thread. Once turbulent flow is reached the pressure to flow relationship is reasonably stable from there on. So what the E-bleeds do at say 30hp per barrel is the same relationship as at 100 hp per barrel. When the flow is laminar as in maybe 10 hp per barrel if you make the E-bleeds function at that flow rate then they will have a different effect upon the mixture. We are only talking about the mains/booster flow here and the E-bleeds. But what we really need to understand is that this laminar flow and turbulent flow happens to every part of the carby where fluid flows.

You might like to calculate the Reynolds number for the Main jet, or the IFR . When the flow swaps from Laminar into Turbulent the pressure needed to produce a flow rate changes. Turbulent flow requires much more energy (higher pressure ). But did the booster all of a sudden change its vacuum generation? To fix that issue you fiddle with the top e-bleed. If you change things so that more air goes through an e-bleed near the surface of the fuel then that air blows fuel toward the booster, sort of like wind whipping up the ocean waves into white caps. It's a very fine point of tune we are talking about, its only just getting fuel out of the booster. In fact you can detect running conditions changing in an engine by blocking the MAB with a ball point pen before any liquid fuel comes from the booster. The air going through the top e-bleed takes some fumes of fuel with it and that alters the tune.
So do we have a lack of velocity in the main well? How would we determine that there is a lack of velocity?
A low velocity is not a problem, its when it transitions to turbulent that is the problem. If we put a 1050 Dominator on our small 5hp lawnmower we will get it to start and it might only require a tiny amount of blade angle to reach maximum power of the engine. So the engine is running on the t-slot , maybe it could pull enough air to get a Booster flowing but its not going to be much fuel from there is it. So how do we set up the E-bleeds on that? We go to WOT on the Lawnmower and the t-slot stops feeding fuel because the air pressure there is now basically Atmospheric and we rely only on the Booster to generate vacuum to feed fuel. Do we need emulsion? What size main jet do we use? Surely the flow through the well will be slow and laminar, so what vacuum needs to be generated by the booster? If laminar requires less energy to flow then we dont need as much vacuum to reach a flow rate. Ok so lets improve the Lawnmower by installing skirted boosters in the venturi on the Dominator. Now we have some decent vacuum for the Booster but also the T-slot is now in more vacuum, Humm. Will the T-slot flow fuel or not? Will it leak air back into the well or not? What size main jet do we use? Should we change the size of the main well? If we make the well smaller we will get higher Reynold number and go to turbulent somewhere in the booster operating range. If that point happens before the T-slot has passed command of the fueling to the booster then we can use the main jet size as the overall controller. If that point happens when the booster is predominant in fueling then we get a step like change in pressure differential required to maintain fueling ratios. That's when you get trouble trying to tune the E-bleeds. Put on a smaller carby and the problem goes away. Its not only the size of the carby , its the relationship of the throttle bore to the venturi and the relationship of the booster vacuum to the throttle bore vacuum at the t-slot. Consistant vacuum generation related to CFM and control of the main jet is what its all about.

Page 1 of 5 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/