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Author:  jmarkaudio [ Sun Jul 11, 2010 9:19 pm ]
Post subject:  Re: Emulsion

I remember the conversation quite well on laminar transitional, and turbulent flow and the fact that gas runs most in the turbulent range, I was more interested on if the velocity of the fuel at the booster exit having an advantage with atomization being higher or lower, or would the booster type whether open like a downleg or annular would be a determining factor. You made the comment that if you replaced the emulsion well with a tube ang kept a similar arrangement of height and size they would operate much the same, but wouldn't the tube still have the advantage with a more even mix of air and fuel? And is there a point in running higher RPM that the advantage would diminish or would i get better? I had conversations with Tuner on the idle/transition circuit acting like a bleed in the mainwell in some cases, is it possible this is one reason why he found using t-slot restrictors advantageous by controlling how much air can be bled back as well as limiting transition fuel to the minimum needed?

I also had another thought, would there be any benefit in sizing the mainwell closer to the needed size, and control the fuel metering at the end of the chain, with a properly sized discharge hole or holes? Take the main jet out of the picture. Probably require some significant changes in the bleed department...

Author:  shrinker [ Sun Jul 11, 2010 11:18 pm ]
Post subject:  Re: Emulsion

The tubes like the Weber system do have an advantage that it can allow more options of e-bleed arrangements than how a Holley is arranged. I mentioned that on that other site but it seems to have gone over some peoples heads and all they want to do is argue about petty things. The tube has an advantage in that it can keep droplets separated so they don't coalesce.
At higher RPM the tube would perform that separation better, if that's what your looking to do.
Whether you have a downleg or an annular. The main difference between the 2 styles is where they gather the inlet air from and what volume passes through the booster. The annular boosters gather the air from higher up towards the entrance of the main venturi and they are a different diameter inside and out etc so there is differences in the mass of air going through the actual booster. So an annular booster has a different vacuum generation relationship to the CFM flowing through the carby. How they operate in a straight bore verses a stock 850 or a stock 750 venturi etc is going to be different. Each job would have to be tested.
A downleg booster has a different fuel delivery technique. It wicks the fuel around the inside of the booster. That effect is very predominant in the stepped boosters. You can see it happening easily.

Your correct on what you said about T-slot restriction jets.

If you reduce the main well size and removed the main jet you wont be able to easily get the fuel curve right to the booster curve. The main well is too long a jet to do that. Jets need to be short, there is a relationship of jet length to diameter that allows a jet to function as a common point restriction with reasonable flow to pressure relationships. Its all in those books by Obert and Larew and Heywood. Tuner used to post the page numbers etc and even scans of them for people. I'm not going to do that. no need.
Back in the beginning of carburetors they didnt have main jets, they just relied upon the sizings of the drilling etc to control the AFR. They even just had a wick in the air stream in some cases. But those systems soon ran into the limitations of engines that had increased RPM ranges. Then they added main jets and used larger drillings, but that reached a limit too. So they went from tubes (like a C&S carby is) to boosters. That made it easy to go to a downdraft design, because more vacuum was generated to lift the fuel. As the flow rates of fuel increased the flow went more turbulent and they needed Boosters to generate more energy, then that became a problem with how to relate the booster signal to the total airflow. Carbys were designed that fitted each engine from an OEM etc and the situation was fine until more powerful cars came along in the 20's until then drivers had to manually adjust the AFR with a lever on the steering wheel. You could richen or lean the engine at will. But then more compression came about and what was needed was an Automatic carby so that drivers who didnt understand didnt stuff up their engines. So emulsion was born in 1926. It made the carby cheaper to build and tune at the end of the production line and the drivers job was easier. Stromberg 97's etc a popular carby from that era are identical in emulsion principal to a Holley of today. Some have combined the emulsion with the old dump tube idea. The dump tube just has a different vacuum generation thats all. You could fit the dump tube with small holes on the end and spread them around a bit to make it all fit then you would have an annular booster or an SV-1. If you remove the main jet and size everything it will run perfectly on a given engine but it will require alteration for every individual engine, That's not a mass production carby. Not suitable for hotrodders. The emulsion well is the thing that makes a hotrodders carby.
Harry Miller invented carbys in the 20's that had multiple main jets in the air stream, Its all been done before.
As a concept you can build a general purpose carby like a Holley is and then learn how to make engine combinations that maximize the power obtainable from how that carby delivers fuel. That is the way the American performance industry has done it. No one altered the carby design they just kept altering the engine design, big ports, small ports, hemi's canted etc. Or you can make a different carby with other features and then figure out how to change the carby to match the engine. That is the way the Europeans have done it. Ever wondered why some people swear by Carter's or Rochester's or Webers or SU's. Its because they have engine combinations that work best with those delivery techniques of fuel.
An engine is not an air pump, its an integrated machine. I dont tune carbys for customers, I integrate their machines.

Author:  nomad [ Thu Jul 15, 2010 9:21 am ]
Post subject:  Re: Emulsion

This has realy been good reading. I appreciate it.

Author:  nomad [ Thu Jul 29, 2010 4:47 pm ]
Post subject:  Re: Emulsion

I've printed out this post and read it a few times now. As I do my best thinking on the lawn mower, I'm finally beginning to get the idea. There are still some things I'd like clarification on so I'll cut the grass tomorrow to formulate my question. :-$

One concept mentioned here strikes me in particular as it syncs with something I thought of a while back. That is, it seems, as it relates to things IC engines, is that what is new is old. That really helps me to understand.

Author:  nomad [ Fri Aug 20, 2010 2:18 pm ]
Post subject:  Re: Emulsion

I've been doing a fair amount of reading on this subject lately. Meaning that I've read the posts contained in this thread and a few other sources. Jmark lent me his copy of Larew's book of which I read a chapter and promptly ordered my own. I've also read two books on tuning Webers and Dellorto carbies. Not the same as what I use but, the basics are the same.

Two things that I saw this week that have helped. 1. I downloaded and studied the chart jmark posted on the vaious Weber emulsions. 2. I read the section in Vizard's book "Carburetors and intake manifolds" that covered emulsion with a couple of really good illustrations.

In Vizard's book he states that in a static situation the fuel level in the main well and emulsion tube are at the same level. When RPMs are increased the level in both drops but, more so in the emulsion tube. It is here and then that the emulsion occurs that slows the flow of fuel and thus leans the mixture. Am I understanding this right? Because if I do I think I may finally get it.

Further, the higher up in the emulson tube the e-holes are the sooner the effects of the air corrector occur. Also, more holes in the lower portions of the emulsion tube the leaner the top end mixture.

So, considering the previous statement, what would prevent me using different size e-holes at the various levels in my BLP blocks to get the fuel curve where I want it?

Sorry to be a bit wordy but, I'm not an engineer or as articulate as I'd like to be.

Author:  shrinker [ Fri Aug 20, 2010 6:36 pm ]
Post subject:  Re: Emulsion

The books read like the reader is an engineer and you've said you have difficulty with that so Ill explain it in a different way and it might help you. First off David Vizard is only telling half the story. This is what Emulsion actually does. First off you have to realize that you cant actually emulsify a gas and a liquid. Emulsion is the wrong word to use. Emulsion applies only to liquids and only to mixing of the liquids. You cant actually mix air with a liquid. What your actually doing is Aeration. using that word will make what happens clearer. So here it is.
The weight of a liquid is termed its density. We will use the word weight just for now because its a non engineering term.
When air bubbles are present in the main well the weight of the liquid in the main well is less than if there was zero air bubbles. Thats it, thats all there is too it, thats as simple as it gets. So now we will discuss what having less weight in the Main well actually does.
There is something that we need to know about liquids and pressure. The thing that causes pressure is the height of the liquid above the point that we measure the pressure at. What this means is that if we go skuba diving and we go down deep into the ocean, the deeper we go the more pressure we have exerted on our body. Some people think its because we have all this tonnage of water on top of us but thats wrong. Imagine this experiment, we get a wine barrel and modify it so that there is a 2 foot diameter tube on the top of it and we fill it all up with water. If the tube is 32 feet long and we fill it to the top the pressure in the barrel will be approx 14.7 PSI. The volume of the water in the tube will be a lot wont it. OK now remove the tube and install one the same length but its only 1/8th inch diameter. Now fill that to the top and the pressure in the barrel will be 14.7 PSI, but the volume of the water in the tube will be stuff all. Pressure has nothing to do with volume, the pressure in the barrel was only because of the height of the water surface. If we compare different liquids, say mercury and we filled the tube to the top we would get a very high pressure in the barrel with mercury and burst the barrel probably. the reason why the pressure is more with Mercury is because Mercury has higher density than water. The correct way to think about pressure is by calculating the height you filled the tube and what density the liquid used was. That is a very important thing to learn, it applies to racing in a lot of different ways that we wont go into now.

I said at the beginning that air bubbles makes it weight less, so now you should be able to see that if we filled the tube on the barrel to the top but we had air bubbles in there the pressure in the barrel would be less. Its pretty simple, the air bubbles weigh virtually nothing and they take up space. If you waited for the air bubbles to rise to the surface and go away, as it did that the level in the tube would drop. Eventually it would all settle out and you would have a new level. The pressure in the barrel will still be the same as when you had air bubbles trapped but now you could see where the level actually is. So you could calculate the pressure accurately. You couldnt calculate it before, when there was air bubbles mixed in there, because you didn't know how much air there was.

The Main jet separates the bowl from the main well. The restriction that the main jet places upon the flow into the main well allows the air to take its place. Think about that sentence for a bit.
When there is air in the main well the fuel on that side of the main jet weighs less (its lower density) so therefore there is a pressure difference change even if the fuel is at the same level either side of the main jet. Its the change in density caused by air bubbles that allows additional control of the flow rate through the main jet. The booster vacuum has to lift the fuel to the height of the tube to get fuel into the engine, so air is used to alter the density so that the vacuum needed to do that is adjustable. You could view it this way if you want to; if you think about our barrel experiment when there was air bubbles in the tube the apparent level was false, that's what air bubbles do in the main well, they make the level of the fuel falsely higher thus making it reach the top easier.
Another thing is that air bubbles in a liquid reduce the viscosity of the liquid. So air bubbles make it flow faster not slower like you say David Vizard claims.

Author:  shrinker [ Fri Aug 20, 2010 7:53 pm ]
Post subject:  Re: Emulsion

Whats important to realize is that the amount of air can be excessive. if the air forms a slug all by itself then its a different story. When the air fills across the entire well and there is no liquids in that space then you have a dramatic shift in density. I should also mention that the air slug will eventually make its way to the barrel. So you ask yourself, if there is only air coming out of the booster at this point in time whats happening with the air that's going through the barrel at this same point in time, Does it have an Air fuel ratio or not?
So its how you balance the flow restriction of the main jet with the amount of air and with the size of the drillings of the well and other passages etc that determines what fuel curve you get. Then you have to add in the incoming flow to the bowl and the air pressure in the bowl. The reason why fuel flows through the main jet is there is a pressure difference from the inlet side to the outlet side of the jet. Its as simple as that. Alter the fuel level in the bowl and you alter the pressure differential and the flow. Alter the air pressure in the bowl and it changes too. Some people need vent flutes other dont. All there doing is correcting an error in the Aeration or the jet sizings.
If things like the scoop disrupt the pressure difference across the main jet and its relationship to the CFM going down the barrel then you have to fix that, not patch it up by sticking a flute on the vent. If people are happy with the easy fix then that's OK but if you want max performance then you have to correct the proper cause of a problem not bandaid it. Scoops might be disrupting the pressure at the Main Air bleed and altering the aeration of the fuel, or they might be disrupting the air flow down the venturi and that means less power. Just because something goes backwards doesn't mean its entirely an instant bad idea. you have to persevere with things until you understand them then you can assess them.

Author:  shrinker [ Fri Aug 20, 2010 8:35 pm ]
Post subject:  Re: Emulsion

Its probably helpful right now to calculate how much fuel we actually put into a cylinder. If the engine dyno says we have a 600hp engine on gasoline running at 0.42 Brake specific fuel consumption. Its telling us that we have 600hp times 0.42 lbs per hour of fuel consumption. The answer is 252lbs of fuel consumed in one hour at that rate of power output. If its doing 7000 RPM to make that 600 hp then the engine will revolve 7000 times in 1 minute, so it will revolve 7000 times 60 in 1 hour. The answer to that is 420,000 revolutions. Because there are 4 intake strokes on a V8per revolution that means there would be 420,000*4 intake strokes per hour. The answer to that is 1,680,000intake strokes. Now if we split that fuel consumed up into those 1,680,000 strokes we have 252 lbs of fuel split up into 1,680,000 strokes so each stroke has 252 divided by 1,680,000. Answer to that is .00015lbs of fuel per intake stroke.
Now you guys can work out how much volume that gasoline weight takes in your imperial system if you want but I do it in metric.
IN metric the answer is the 600hp engine has 0.0907cc's per intake stroke. That's not quite 1/10th of a cc. Not much huh. So what do you recon that slug of air in the main well that's 10mm's long and 6mm diameter is going to do?

Author:  nomad [ Fri Aug 20, 2010 9:04 pm ]
Post subject:  Re: Emulsion

Thanks shrinker, your explaination clears a few things up for me.

Author:  jmarkaudio [ Sun Aug 22, 2010 12:47 pm ]
Post subject:  Re: Emulsion

I guess that has been the point of my questions with a needle tube emulsion, getting the fuel quantity leaving the booster to be more consistent, it will allow the jet to be leaned out as you don't have to over fuel to make up for lean pockets. And the point Tuner always made on tuning the carb with the correct air and emulsion to tune the fuel curve correct for the engine.

Author:  shrinker [ Sun Aug 22, 2010 6:26 pm ]
Post subject:  Re: Emulsion

There is nothing secretive about the benefits of tube emulsion. Just about every other carby maker in the world uses tubes. Just look at Weber tubes and you will see things that are not possible to do with the original Holley design brief. The problem is racing rules that wont allow carburetors other than Holleys or BG's in some classes. You guys have rules that restrict brand usage in top classes like Prostock etc so the trickle down effect to other racing classes is contaminated right from the top. Holleys are a fine carby but they are compromised in some areas in order to be a modular, cheap to produce design.

Author:  nomad [ Mon Sep 13, 2010 10:18 am ]
Post subject:  Re: Emulsion

Some runs on my 1050 on Sept 4th and September 11th. Carb is still a little fat throughout the pass both weekends. Notes in the logs will allow the viewer to see the tune and changes made.

It's way fat in the burnout. Not sure why that is. Staring at the logs long enough may show me the the cause and solution.

Author:  shrinker [ Mon Sep 13, 2010 6:11 pm ]
Post subject:  Re: Emulsion

Some of the logs show the AFR richening up before you back off the throttle. It looks like your backing off to save the index or whatever. One of the logs shows it leaning off at the last bit of the top end. So whats going on with all these things?
Also you have you saved it with smoothing. What do the non smoothed logs look like?

Author:  shrinker [ Mon Sep 13, 2010 6:13 pm ]
Post subject:  Re: Emulsion

What fuel is this?

Author:  Scott Smith [ Mon Sep 13, 2010 7:47 pm ]
Post subject:  Re: Emulsion

shrinker wrote:
What fuel is this?

Pump gas

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