Annular boosters on a Tunnel Ram

-
Post #45.
' Larger air bleed starts the mains sooner '. Nope. When RB quoted the info from post #41 into his post #45, he got it wrong. What post #41 said: ' With more air coming in the bleed...'.
A vital but important distinction. What causes 'more air' to come through the [
air ] bleed? More depression [ suction ] in the venturi.......which is created by an increase in air speed....which is created by the engine rpm increasing. It should be obvious that if the AB is made smaller, less engine rpm is needed to overcome the loss of signal to the booster. A smaller AB starts the system sooner....
Do you guys really think increasing the AB from 0.030" to 0.032" [ 7% more ] is going to make some huge difference in how the fuel is lifted to the booster? It sure will affect when the system starts.

Claiming the quote from Taylor in post #22 'confirms' that a larger MAB size starts the main system earlier is reading something that isn't there. It says nothing of the sort.
There is no mention of AB sizing in Philip Smith's book.
And once again....
' The function of the air bleed is not solely to emulsify fuel. It also exerts control over fuel flow by " bleeding off" some of the suction force or fuel metering signal that is developed at the discharge nozzle. ....As the air bleed is enlarged, the vacuum reqd to initiate fuel flow is increased. Conversely a reduction in air bleed size reduces vacuum signal requirements & fuel flow is more easily initiated'
 
Post #45.
' Larger air bleed starts the mains sooner '. Nope. When RB quoted the info from post #41 into his post #45, he got it wrong. What post #41 said: ' With more air coming in the bleed...'.
A vital but important distinction. What causes 'more air' to come through the [
air ] bleed? More depression [ suction ] in the venturi.......which is created by an increase in air speed....which is created by the engine rpm increasing. It should be obvious that if the AB is made smaller, less engine rpm is needed to overcome the loss of signal to the booster. A smaller AB starts the system sooner....
Do you guys really think increasing the AB from 0.030" to 0.032" [ 7% more ] is going to make some huge difference in how the fuel is lifted to the booster? It sure will affect when the system starts.

Claiming the quote from Taylor in post #22 'confirms' that a larger MAB size starts the main system earlier is reading something that isn't there. It says nothing of the sort.
There is no mention of AB sizing in Philip Smith's book.
And once again....
' The function of the air bleed is not solely to emulsify fuel. It also exerts control over fuel flow by " bleeding off" some of the suction force or fuel metering signal that is developed at the discharge nozzle. ....As the air bleed is enlarged, the vacuum reqd to initiate fuel flow is increased. Conversely a reduction in air bleed size reduces vacuum signal requirements & fuel flow is more easily initiated'



Last paragraph. It depends on pressure differential. At low air flows the MAB acts like emulsion and starts the mains sooner.


I said the MATH is in the Obert and Smith books.

You are wrong. Tuner and Shrinker say you are wrong.
 
Nope, not wrong & neither do Shrinker/Tuner say I am wrong. Quote where S & T say: a larger MAB starts the system sooner.

From D. Vizard:
[1] His Holley book, p. 86: ' ..changing the size of the main cct high speed bleed changes the slope, so if the mixture is leaner at the top end, reducing the size of the AB richens the mixture'

[2] How to build HP, vol2, P. 71, Holley section: Description of idle cct, followed by: 'As with the main cct, larger [ air bleeds ] leans out the mixture & smaller richens.'
p. 102: ' More than likely,, the fuel will richen or lean lout as rpm increases. If it shows a tendency to lean, reduce the air corrector size & do the reverse if it richens..'
 
Nope, not wrong & neither do Shrinker/Tuner say I am wrong. Quote where S & T say: a larger MAB starts the system sooner.

From D. Vizard:
[1] His Holley book, p. 86: ' ..changing the size of the main cct high speed bleed changes the slope, so if the mixture is leaner at the top end, reducing the size of the AB richens the mixture'

[2] How to build HP, vol2, P. 71, Holley section: Description of idle cct, followed by: 'As with the main cct, larger [ air bleeds ] leans out the mixture & smaller richens.'
p. 102: ' More than likely,, the fuel will richen or lean lout as rpm increases. If it shows a tendency to lean, reduce the air corrector size & do the reverse if it richens..'

Ok, lie to yourself all you want. I know what Tuner says.

And your worn out quotes don’t address pressure differentials at low air flows.

Get that through your head.
 
All yall's bullshit just makes me want to ask my questions less and less.
 
RB,
You know what Tuner says? So do I, I have read it. And it is NOT what you say he says.

Why don't you tell us all about pressure differentials at low air flows???????????????? I am sure DV would like to know as would many others.....
 
RB,
You know what Tuner says? So do I, I have read it. And it is NOT what you say he says.

Why don't you tell us all about pressure differentials at low air flows???????????????? I am sure DV would like to know as would many others.....

You are talking out of your hat. I can tell you 100% what Tuner says. That’s a FACT.

Maybe you need to follow the link that Hysteric posted a while back (it was in a different forum but it’s on FABO) and it has (IIRC) a huge amount of Tuner and Shrinker carb info.

Do that and you’ll find they don’t agree with you, because YOU are wrong.

In fact, because it’s a new year I’ll see if I can find it and link it here.
 
Reading this on Maxperformance website. Maybe it helps, maybe it causes more confusion.

Tom Vought (Holley Engineer) and Tuner:

Today I am going to throw some SERIOUS CARB THEORY at you.
If you are not interested in that area of carb tuning, see you tomorrow. Tom V.


Tuner: “On carbs it's very important that the correct two-phase flow gets established during emulsion. Otherwise you will see RPM dependency of AFR.” I see your remark as a profound understatement. Incorrect two-phase flow is at the root of all this aggravation.

People who have drill bits but don’t know why to use them have been molesting innocent carburetors for a long time. Now some of them are in charge of the manufacture of new carbs and they think they have improved them by using larger drill bits to make the air bleed and “emulsion” orifices. I guess the guys that engineered the original carburetors on the old muscle cars were pretty stupid or they would have “improved the emulsion” 40 or 50 years ago when they had their chance.

Basically TUNER is saying that after the mid 80s the people from Holley went other places and the BASIC Knowledge was lost. Marvin Beniot (later Quick Fuel Owner), Chuck Gulledge, Louis Lucas, Steve White, Marty Brown, Jeff Komar, were all old school Holley carb people. The new guys that went to The south (with Holley Aftermarket, basically were unable to do the job and the company went banklrupt the FIRST TIME. (They went bankrupt several times). TV

TUNER: It is well documented that introducing air into the main well encourages low signal flow and can encourage or discourage high signal flow. The natural characteristic of a plain jet and nozzle (no air) is to get richer as airflow increases. The purpose of the air bleed system is to modify that behavior to accomplish a constant (or the desired) air/fuel ratio over as wide a range of airflows as possible. The particular ratios for power and cruise are realized by the selection of jet and rod or jet and auxiliary jet (power valve channel). The purpose of air bleeds is not to emulsify but to accomplish the correct fuel delivery. Emulsion is just a beneficial side effect.

This is a very true statement That is why some CARB PEOPLE call the Air Bleeds "AIR CORRECTORS" TV

What I’m going on about here is Klaus’ remark about “correct two-phase flow”. That is the description of a fluid flow that is made up of a liquid and a gas flowing together in the same conduit. As the ratio of gas to liquid increases (more gas, less liquid), at some point the gas bubbles coalesce from many small ones into a few big ones and the flow starts to “slug” and become erratic. The carburetor nozzle spits like a garden hose with air in it when there is too much “emulsion” air.

An emulsion of air and fuel has reduced density, surface tension and viscosity compared to fuel alone. This increases the flow of fuel considerably, particularly in low-pressure difference operation, at low throttle openings or lower engine speeds. Just how much of an increase (richer) is dependant upon where and how much air is introduced into the fuel flow.

Mainly, what must be understood is that because the fuel discharge nozzle connects the venturi to the main well, whatever the low pressure (vacuum) is in the venturi, it is also the pressure in the main well. The air bleed is in the carb air horn or somewhere else where it is exposed to essentially atmospheric pressure, which is higher than the venturi pressure. This pressure difference causes air from the air bleed to flow through the emulsion system into the main well and to the nozzle. The flow of air can have very high velocities, approaching sonic in some orifices. The airflow literally blows the fuel toward and through the nozzle. A larger main air bleed will admit more air to the emulsion system and that can increase or decrease fuel flow to the engine. The size, number and location of the other air holes in the emulsion system, the size of the main well flow area, the size of the nozzle and the specific pressure difference at the moment are the determining factors. The ratios of air volume to fuel volume to flow area, with the air volume's expansion with the venturi velocity induced pressure reduction being the key. The bubbles expand as the pressure drop increases with airflow.

The fuel flow through the main jet is the result of the pressure difference between the atmospheric pressure in the float bowl and the venturi air velocity induced vacuum acting on the nozzle and the main well. The venturi vacuum in the well is reduced (the pressure is raised) by the "air leak" from the air bleed. This reduces the pressure difference that causes the flow through the main jet. If the air bleed were big enough, the pressure in the well would be the same as in the float bowl and no fuel would flow. Think about drinking through a soda straw with a hole in it above liquid level. Bigger hole, less soda. Suck harder, not much more soda. Big enough hole, no soda. This is the means by which the emulsion system can "lean it out on the top end". Incidentally, the vacuum that lifts water up a soda straw is in the most sensitive operating range for emulsion systems.

It is in the lowest range of throttle opening, at the start of main system flow, that the effect of adjusting the introduced emulsion air (and it's effect in increasing the main fuel flow) is most critical. Small changes can have large and sometimes unexpected or counter-intuitive consequences. The goal is to seamlessly blend the rising main flow with the declining idle/transition system fuel delivery to accomplish smooth engine operation during opening of the throttle in all conditions, whether from curb idle or any higher engine speed. The high speed and load mixture correction is usually easily accomplished, in comparison.

The vertical location of the bleeds entering the main well influences the fuel flow in the following ways.

1: Orifices above float level or between the well and the nozzle allow bled air to raise the pressure (reduce the vacuum) in the nozzle and above the fuel in the well. That delays the initial start of fuel flow from the nozzle to a higher air flow through the venturi and is used to control the point in the early throttle opening where the main starts.

2: Orifices at float level increase low range (early throttle opening) fuel flow by carrying fuel with the airflow to the nozzle.

3: Orifices below float level increase fuel flow by the effect of lowering the level of fuel in the well to the hole(s) admitting air. This is like raising the float level a similar amount (increases the effect of gravity in the pressure difference across the main jet) and also adds to the airflow carrying fuel to the nozzle. Locating the orifices at different vertical positions influences this effect’s progression.

4: The "emulsion holes" influence is greatest at low flows and the "main air bleed" has most influence at high flows.

In the first three cases above, once fuel flow is established it is greater than it would be with fewer or smaller holes. Visualize wind blowing spray off of the top of water waves. It doesn’t take much pressure difference to cause the velocity of the airflow through the bleed orifices to have significant velocity in the orifice, even approaching sonic (1100 F.P.S.) if the orifices are small. The phenomena of critical flow is what limits the total air flow through an orifice and allows tuning by changing bleed size.

Essentially, the emulsion effect will richen the low flow and the air bleed size, main well and nozzle restrictions will control the increase or reduction of high flow. Again, the desired air/fuel ratio is the primary purpose of the bleed system. "Improved emulsion" is an oxymoron if the modification of air bleeds to "improve emulsion" results in an incorrect air/fuel ratio in some range of engine operation. Correct proportioning of all the different bleeds (and, of course, the idle, transition and power circuits) will give the correct air/fuel ratios over the total range of speeds and loads and a flat air/fuel ratio characteristic at wide open throttle.

A little simpler, the airbleeds and emulsion are used to set the fuel curve in a Holley. The 3rd e-hole will make it a little more active at the low end, and possibly a little lean up top depending on the main air bleed used. If you look at the 2 circuit conversion thread, you can set your 8082 metering up at the starting point in the thread even though it is already a 2 circuit carb. After that you HAVE to adjust the metering for your engine as to what it wants to get the best performance, but in most cases it will be close. Your iron head 468 is no different than some of the other combo's here, everything from milder small blocks to some killer engine., Unless the combination is bad, poor cam design or the ICL is way off, timing is way off, plugs are too cold... etc, it should be close enough to start with. Learn to properly read the plugs and invest in a wideband O2 if you can, it will help you find the most out of it.

Tom V.

ps I did not feel like typing all of this stuff in my words when TUNERS were most likely would say it better. Tom V.
 
More about annular boosters:

The Holley Main System is made up of two major components:
The Annular Discharge Booster Assembly (talking about modern Carb Design stuff vs the old "Straight Leg Boosters" in this post) and the Main Air Well System.

The Annular Discharge Booster Design induces higher air velocities at the point of the discharge which results in increased signal strength to the Main System. The configuration of booster and the size of the booster assembly was established by running signal strength measurements fuel flow curves, and fuel discharge profiles on Holley Engineering's Wet Flow Benches in Warren Michigan.

The total airflow of the carbs was reduced slightly, the target was to have no reduction of airflow. Most Annular Discharge Designs will flow approximately 5 cfm less per booster position so on a 850 cfm carb with the annular boosters the air flow would be 830 cfm.

The Main Well operation is the same as the Idle System.

The High Speed Air Bleed meters the "bleed air" to the Main Well. The "bleed air" is fed thru holes in the metering block (emulsion holes) and form a homogeneous fuel/air mixture that is then discharged thru the Annular Booster assembly.

Obviously the High Speed Air Bleed is a "calibration item". The Main Fuel Jet is the "calibration orifice" for the fuel from the fuel bowl.
The High Speed Air Bleed is determined based on the range of Main Jets determined by the Calibration Strategy and Engine Dynamometer data.

The Idle Jet (Idle Feed Restriction) is determined by the approximate fuel required to power the engine in the Idle and off-idle speed ranges.

The diameter of the Bleed Holes (emulsion holes) and number and position of those holes have a direct effect on the vehicle "drive characteristics"
The Top Hole(s) affect crowd and part throttle acceleration response. The Bottom Hole(s) are used to initiate and accelerate the Main circuit fuel and air flow thru the booster.

NOTE: Changes made to the Air Bleeds, for fuel curve contouring, DO NOT REQUIRE changes in the emulsion holes

A change in the Main Jets will require a potential change in the air bleed holes at times. This is a calibration tuning effect.

If the proper balance between the Main Jets and the Air Bleeds is not maintained, a depreciation in vehicle driveability will result.
The Fuel/Air System of a Holley carburetor may be classified as a tuned circuit carburetor and will be extremely stable and responsive to engine mode changes if proper methods of tuning are observed. A Air/Fuel meter is recommended.

Tom V.
 
Reading this on Maxperformance website. Maybe it helps, maybe it causes more confusion.

Tom Vought (Holley Engineer) and Tuner:

Today I am going to throw some SERIOUS CARB THEORY at you.
If you are not interested in that area of carb tuning, see you tomorrow. Tom V.


Tuner: “On carbs it's very important that the correct two-phase flow gets established during emulsion. Otherwise you will see RPM dependency of AFR.” I see your remark as a profound understatement. Incorrect two-phase flow is at the root of all this aggravation.

People who have drill bits but don’t know why to use them have been molesting innocent carburetors for a long time. Now some of them are in charge of the manufacture of new carbs and they think they have improved them by using larger drill bits to make the air bleed and “emulsion” orifices. I guess the guys that engineered the original carburetors on the old muscle cars were pretty stupid or they would have “improved the emulsion” 40 or 50 years ago when they had their chance.

Basically TUNER is saying that after the mid 80s the people from Holley went other places and the BASIC Knowledge was lost. Marvin Beniot (later Quick Fuel Owner), Chuck Gulledge, Louis Lucas, Steve White, Marty Brown, Jeff Komar, were all old school Holley carb people. The new guys that went to The south (with Holley Aftermarket, basically were unable to do the job and the company went banklrupt the FIRST TIME. (They went bankrupt several times). TV

TUNER: It is well documented that introducing air into the main well encourages low signal flow and can encourage or discourage high signal flow. The natural characteristic of a plain jet and nozzle (no air) is to get richer as airflow increases. The purpose of the air bleed system is to modify that behavior to accomplish a constant (or the desired) air/fuel ratio over as wide a range of airflows as possible. The particular ratios for power and cruise are realized by the selection of jet and rod or jet and auxiliary jet (power valve channel). The purpose of air bleeds is not to emulsify but to accomplish the correct fuel delivery. Emulsion is just a beneficial side effect.

This is a very true statement That is why some CARB PEOPLE call the Air Bleeds "AIR CORRECTORS" TV

What I’m going on about here is Klaus’ remark about “correct two-phase flow”. That is the description of a fluid flow that is made up of a liquid and a gas flowing together in the same conduit. As the ratio of gas to liquid increases (more gas, less liquid), at some point the gas bubbles coalesce from many small ones into a few big ones and the flow starts to “slug” and become erratic. The carburetor nozzle spits like a garden hose with air in it when there is too much “emulsion” air.

An emulsion of air and fuel has reduced density, surface tension and viscosity compared to fuel alone. This increases the flow of fuel considerably, particularly in low-pressure difference operation, at low throttle openings or lower engine speeds. Just how much of an increase (richer) is dependant upon where and how much air is introduced into the fuel flow.

Mainly, what must be understood is that because the fuel discharge nozzle connects the venturi to the main well, whatever the low pressure (vacuum) is in the venturi, it is also the pressure in the main well. The air bleed is in the carb air horn or somewhere else where it is exposed to essentially atmospheric pressure, which is higher than the venturi pressure. This pressure difference causes air from the air bleed to flow through the emulsion system into the main well and to the nozzle. The flow of air can have very high velocities, approaching sonic in some orifices. The airflow literally blows the fuel toward and through the nozzle. A larger main air bleed will admit more air to the emulsion system and that can increase or decrease fuel flow to the engine. The size, number and location of the other air holes in the emulsion system, the size of the main well flow area, the size of the nozzle and the specific pressure difference at the moment are the determining factors. The ratios of air volume to fuel volume to flow area, with the air volume's expansion with the venturi velocity induced pressure reduction being the key. The bubbles expand as the pressure drop increases with airflow.

The fuel flow through the main jet is the result of the pressure difference between the atmospheric pressure in the float bowl and the venturi air velocity induced vacuum acting on the nozzle and the main well. The venturi vacuum in the well is reduced (the pressure is raised) by the "air leak" from the air bleed. This reduces the pressure difference that causes the flow through the main jet. If the air bleed were big enough, the pressure in the well would be the same as in the float bowl and no fuel would flow. Think about drinking through a soda straw with a hole in it above liquid level. Bigger hole, less soda. Suck harder, not much more soda. Big enough hole, no soda. This is the means by which the emulsion system can "lean it out on the top end". Incidentally, the vacuum that lifts water up a soda straw is in the most sensitive operating range for emulsion systems.

It is in the lowest range of throttle opening, at the start of main system flow, that the effect of adjusting the introduced emulsion air (and it's effect in increasing the main fuel flow) is most critical. Small changes can have large and sometimes unexpected or counter-intuitive consequences. The goal is to seamlessly blend the rising main flow with the declining idle/transition system fuel delivery to accomplish smooth engine operation during opening of the throttle in all conditions, whether from curb idle or any higher engine speed. The high speed and load mixture correction is usually easily accomplished, in comparison.

The vertical location of the bleeds entering the main well influences the fuel flow in the following ways.

1: Orifices above float level or between the well and the nozzle allow bled air to raise the pressure (reduce the vacuum) in the nozzle and above the fuel in the well. That delays the initial start of fuel flow from the nozzle to a higher air flow through the venturi and is used to control the point in the early throttle opening where the main starts.

2: Orifices at float level increase low range (early throttle opening) fuel flow by carrying fuel with the airflow to the nozzle.

3: Orifices below float level increase fuel flow by the effect of lowering the level of fuel in the well to the hole(s) admitting air. This is like raising the float level a similar amount (increases the effect of gravity in the pressure difference across the main jet) and also adds to the airflow carrying fuel to the nozzle. Locating the orifices at different vertical positions influences this effect’s progression.

4: The "emulsion holes" influence is greatest at low flows and the "main air bleed" has most influence at high flows.

In the first three cases above, once fuel flow is established it is greater than it would be with fewer or smaller holes. Visualize wind blowing spray off of the top of water waves. It doesn’t take much pressure difference to cause the velocity of the airflow through the bleed orifices to have significant velocity in the orifice, even approaching sonic (1100 F.P.S.) if the orifices are small. The phenomena of critical flow is what limits the total air flow through an orifice and allows tuning by changing bleed size.

Essentially, the emulsion effect will richen the low flow and the air bleed size, main well and nozzle restrictions will control the increase or reduction of high flow. Again, the desired air/fuel ratio is the primary purpose of the bleed system. "Improved emulsion" is an oxymoron if the modification of air bleeds to "improve emulsion" results in an incorrect air/fuel ratio in some range of engine operation. Correct proportioning of all the different bleeds (and, of course, the idle, transition and power circuits) will give the correct air/fuel ratios over the total range of speeds and loads and a flat air/fuel ratio characteristic at wide open throttle.

A little simpler, the airbleeds and emulsion are used to set the fuel curve in a Holley. The 3rd e-hole will make it a little more active at the low end, and possibly a little lean up top depending on the main air bleed used. If you look at the 2 circuit conversion thread, you can set your 8082 metering up at the starting point in the thread even though it is already a 2 circuit carb. After that you HAVE to adjust the metering for your engine as to what it wants to get the best performance, but in most cases it will be close. Your iron head 468 is no different than some of the other combo's here, everything from milder small blocks to some killer engine., Unless the combination is bad, poor cam design or the ICL is way off, timing is way off, plugs are too cold... etc, it should be close enough to start with. Learn to properly read the plugs and invest in a wideband O2 if you can, it will help you find the most out of it.

Tom V.

ps I did not feel like typing all of this stuff in my words when TUNERS were most likely would say it better. Tom V.


That FOURTH paragraph is what I have been saying the WHOLE TIME. And yet, people want to argue it.

It is WELL DOCUMENTED that introducing air into the main well encourages low signal flow.

How hard is that to grasp? A bigger MAB will START the mains sooner and lean the fuel curve at high air flows (through the booster).

Just like I said and just like my testing has shown.

And Shrinker agrees with this.
 
Nevermind. I'll just find out on my own by trial and error and I won't share what I find out.
 
RB,
Nope, still getting it wrong & Shrinker doesn't agree with this fact: a larger MAB starts the system later, not earlier.
If you bothered to read post #58 fully, you would have seen the straw/liquid experiment mentioned, which I posted waaaaay back in this thread.

From post #58:
' A larger MAB will admit more air to the emulsion system & that can increase or decrease the fuel flow to the engine'.

and...

The venturi vacuum in the well is reduced by the 'air leak' [ highlighted in the original ] from the AB & this reduces the pressure difference that causes the flow through the main jet'

He then mentions the straw experiment to explain how the MAB works. It is not that hard....
 
RB,
Nope, still getting it wrong & Shrinker doesn't agree with this fact: a larger MAB starts the system later, not earlier.
If you bothered to read post #58 fully, you would have seen the straw/liquid experiment mentioned, which I posted waaaaay back in this thread.

From post #58:
' A larger MAB will admit more air to the emulsion system & that can increase or decrease the fuel flow to the engine'.

and...

The venturi vacuum in the well is reduced by the 'air leak' [ highlighted in the original ] from the AB & this reduces the pressure difference that causes the flow through the main jet'

He then mentions the straw experiment to explain how the MAB works. It is not that hard....


Ok. But that’s NOT what it says and YOU know that.
 
RB,
What I know is what it says in post #58 & it is correct. Same as what I have said. Tom Vaught [ not Vought ] is a university trained engineer who worked for Holley during the glory years, & then spent decades at Ford before retiring. We correspond via email. He told me Mike Urich, Holley book author, was an excellent engineer.
 
So, this is my interpretation from my post 58. A larger air bleed will start the system sooner as more air will increase the pressure difference and start the fuel to flow. This will also lean out the WOT. If the air bleed was increased too far, it eventually will flow no fuel. I also believe each set up will need its own mix, so each application will need its own experimentation to find the correct set up. O² sensors can misrepresent as to what the burn is actually doing. A lean reading can be a result of fuel and O² not mixing due to timing, flame propagation misfire, etc. Testing will need to be done. It was told to me by an engineer at work...think of fuel and O² molecules at a dance. The idea is to have gas and O² to be able to find their dance partner. Sometimes there isn't time to match up. It is far better to have too much gas and ensure all O² has a partner (rich) vs not enough (lean).

The fuel flow through the main jet is the result of the pressure difference between the atmospheric pressure in the float bowl and the venturi air velocity induced vacuum acting on the nozzle and the main well. The venturi vacuum in the well is reduced (the pressure is raised) by the "air leak" from the air bleed. This reduces the pressure difference that causes the flow through the main jet. If the air bleed were big enough, the pressure in the well would be the same as in the float bowl and no fuel would flow. Think about drinking through a soda straw with a hole in it above liquid level. Bigger hole, less soda. Suck harder, not much more soda. Big enough hole, no soda. This is the means by which the emulsion system can "lean it out on the top end". Incidentally, the vacuum that lifts water up a soda straw is in the most sensitive operating range for emulsion systems.
 
So, this is my interpretation from my post 58. A larger air bleed will start the system sooner as more air will increase the pressure difference and start the fuel to flow. This will also lean out the WOT. If the air bleed was increased too far, it eventually will flow no fuel. I also believe each set up will need its own mix, so each application will need its own experimentation to find the correct set up. O² sensors can misrepresent as to what the burn is actually doing. A lean reading can be a result of fuel and O² not mixing due to timing, flame propagation misfire, etc. Testing will need to be done. It was told to me by an engineer at work...think of fuel and O² molecules at a dance. The idea is to have gas and O² to be able to find their dance partner. Sometimes there isn't time to match up. It is far better to have too much gas and ensure all O² has a partner (rich) vs not enough (lean).

The fuel flow through the main jet is the result of the pressure difference between the atmospheric pressure in the float bowl and the venturi air velocity induced vacuum acting on the nozzle and the main well. The venturi vacuum in the well is reduced (the pressure is raised) by the "air leak" from the air bleed. This reduces the pressure difference that causes the flow through the main jet. If the air bleed were big enough, the pressure in the well would be the same as in the float bowl and no fuel would flow. Think about drinking through a soda straw with a hole in it above liquid level. Bigger hole, less soda. Suck harder, not much more soda. Big enough hole, no soda. This is the means by which the emulsion system can "lean it out on the top end". Incidentally, the vacuum that lifts water up a soda straw is in the most sensitive operating range for emulsion systems.

I wouldn’t call that your “interpretation” because you nailed it.

Thats exactly what it says, and that’s exactly how it works.

Its almost absurd watching a simple definition of how the MAB functions get so twisted up that it becomes convoluted.

The main air bleed can (and does) behave exactly as described above because (once again, exactly what it says in the text) the pressure differential across the booster and the MAB are different at different air flows.

Thats why a bigger MAB will START the mains SOONER and still make the fuel curve tilt leaner at higher air flows.

Evidently some can’t grasp the pressure differential at different air flows.

Regardless of all that, it’s really simple to test MAB function. All one needs to do is test it and you’ll find that Tuner’s explanation is exactly how it works.

Of course, I have the luxury of getting the phone and talking to Tuner to make sure I’m understanding what he wrote.

And your explanation is exactly what Tuner says and is exactly what happens in the real world.

I hope this ENDS all this BULLSHIT about MAB functions as it’s exhausting to keep unscrewing the bad information about it.

I have personally posted the GENERAL definition of it by Taylor. Of course, if you want the full explanation you need to get the books and read all of it. And grab a scientific notation calculation and work through the math of it. That makes crystal clear what is happening when you change the MAB.

This is PRECISELY how “holleyitis” happens. Bad information repeated over and over and over bolstered by misquotes, nonsense and repeated error.

This stuff is easily understood if you read what guys like Tuner and Shrinker have written. They have made it very simple.

You just have to shut out the noise and ignore those who say something diametrically opposed to what they are saying.
 
So, question then, I would be able to try the "wire test", thin wire inserted into the MAB to reduce the size quickly and easily to see if it gets better or worse as I don't have a dyno, data logger, or O² sensors, yes? This would tell me if the bleed needs to be smaller (later to start and richer at WOT) or larger depending on how the car reacted. This would also then tell me why it worked better vs it just did.
 
Got a tick of preliminary data this morning. First drive with the the new main bodies. Wasn’t able to get any solid data due to time and weather conditions but…

Low speed cruise under say 35mph: no change. Still a bit on the rich side but not too terrible.

Mid range cruise 35-60mph dropped 1-2 numbers in AFR. At the 60mph before was 15.5 to 16 is now 14.

Cruise dropped 1.5 from 14 to 12.5

WOT is down to under 11 AFR.

Light acceleration, dead stop to 40 mph is down almost 2 full points from the 14’s down in the 12-13 now.

This is all preliminary due to not having a copilot to help jot down #’s, and time to get solid readings. Really smooth though. Hopefully get some decent weather soon.
 
"Small changes can have large and sometimes unexpected or counter-intuitive consequences."
This quote about emulsion/main air bleed for me sums it up. Like most things there are exceptions to rules that are combination specific. I think it has to do with when air flow through an orifice becomes restricted by the size of the orifice.
 
Got a tick of preliminary data this morning. First drive with the the new main bodies. Wasn’t able to get any solid data due to time and weather conditions but…

Low speed cruise under say 35mph: no change. Still a bit on the rich side but not too terrible.

Mid range cruise 35-60mph dropped 1-2 numbers in AFR. At the 60mph before was 15.5 to 16 is now 14.

Cruise dropped 1.5 from 14 to 12.5

WOT is down to under 11 AFR.

Light acceleration, dead stop to 40 mph is down almost 2 full points from the 14’s down in the 12-13 now.

This is all preliminary due to not having a copilot to help jot down #’s, and time to get solid readings. Really smooth though. Hopefully get some decent weather soon.
This data is just with a main body change? All other components the same as before? Just curious
 
So, question then, I would be able to try the "wire test", thin wire inserted into the MAB to reduce the size quickly and easily to see if it gets better or worse as I don't have a dyno, data logger, or O² sensors, yes? This would tell me if the bleed needs to be smaller (later to start and richer at WOT) or larger depending on how the car reacted. This would also then tell me why it worked better vs it just did.
Yup, that’s exactly what the wire test does. Just make sure to pinch the wire under the air cleaner lid so it doesn’t get pulled in the engine.
 
This data is just with a main body change? All other components the same as before? Just curious
Dropped Primary main jets from 74-70
and secondaries from 84-80 all other specs the same.

B09DC263-8660-46EE-833B-83220B1858FF.jpeg
 
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