Annular boosters on a Tunnel Ram

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Well you didn't say that in post #87... You just said the MAB starts the main system sooner. No mention of the MAB being bigger or smaller. That was what I was querying....

Oh, & I am following....& I have had real world experiences as well.
 
Bewy said:
Well you didn't say that in post #87... You just said the MAB starts the main system sooner. No mention of the MAB being bigger or smaller. That was what I was querying....

Oh, & I am following....& I have had real world experiences as well.
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What happens in threads like this is you continually post bullshit, argue, refuse to accept what the people who pioneered carb science say.

Then when the actual words of guys like Tuner (who I know for a FACT has been doing this stuff since for 60 years or more because I met him as a 6-7 year old kid in about 1969 when my dad had his distributor machine) Shrinker are posted you slip and slide around.

Its near impossible to keep track of what you post. I’ve posted it incorrectly several times because all your posts just ramble.

For the sake of clarity and accuracy I’ll post it one more time and then I’m out because you can’t learn or won’t unlearn what you have in error.

A larger MAB will start the mains SOONER and tilt the fuel curve LEANER at HIGHER flows.

A smaller MAB will DELAY the start of the mains and tilt the fuel curve RICHER at HIGHER flows.

It can’t be said any more simple than that.
 
Bewy said:
Well you didn't say that in post #87... You just said the MAB starts the main system sooner. No mention of the MAB being bigger or smaller. That was what I was querying....

Oh, & I am following....& I have had real world experiences as well.
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You’re correct I didn’t say it. Semantics be damned. Had you been following the conversation it would have been clear. But you were, and I know you were, hence “but you knew that”. You’re just throwing stones.
 
71GSSDemon said:
I guess my comments and thoughts come from these below. It seems clear to me. From post 58

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.

Here we are discussing main jet and WOT mentioning the larger air bleed, if increased in size, will lessen flow due to pressure difference. This speaks to the MAB being larger, less flow will happen - to the point of no flow if too large. Being the MAB is above the well of fuel.

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".

Bewy, please, I am trying to understand this. If you are reading these statements from Tuner differently, can you please quote the words specifically and explain your understanding?

@MomsDuster Sorry for hijacking your thread with all of this, but I also hope we get some info posted that does help.
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@Bewy as asked above: please, I am trying to understand this. If you are reading these statements from Tuner differently, can you please quote the words specifically and explain your understanding? It is evident that you are reading this and other information different than most. Can you provide documentation, dyno test results, etc to back up your views that a larger MAB delays the mains and richens the WOT afr? It seems clear to my understanding of what Tuner and others are saying in what I posted in 58 and quoted above. Maybe we can put the fighting to an end.
 
RB/TT5,

I have posted TWO quotes, one from Holley engineer Mike Urich & one from Dave Emanuel's Carter book that state that a smaller MAB starts the system sooner. That part of it is simple high school physics, as shown with the straw example.

Despite all the blustering & hoo-ha from RB, nobody, repeat nobody, has reproduced or linked a statement to Shrinker/Tuner that states a bigger MAB starts the main system sooner.
 
71GSS,
Post #104. I have provided two quotes earlier in this thread [ referred to in post #105 ] that that show a smaller MAB starts the system the earlier. A larger MAB will lean the mixture at WOT, not richen it.
 
Bewy, I see the straw comparison, it is in my posts as well for leaning out WOT. We agree a larger MAB will lean WOT. Once fuel is flowing, and throttle blades are open, the pressure differences limit or even stop flow.

I do not see the post referencing how a larger MAB will start the mains sooner. To me the quote...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. says it will start sooner.

I am not arguing. Just trying to understand where you are coming from.
 
71GSSDemon said:
Bewy, I see the straw comparison, it is in my posts as well for leaning out WOT. We agree a larger MAB will lean WOT. Once fuel is flowing, and throttle blades are open, the pressure differences limit or even stop flow.

I do not see the post referencing how a larger MAB will start the mains sooner. To me the quote...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. says it will start sooner.

I am not arguing. Just trying to understand where you are coming from.
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I spent some hours last night on the dyno testing booster startup point in rpms vs main air bleed size. I tested at no load, high 40's and mid 60's ftlbs torque. My results were that booster startup occurred within 100 rpm regardless of main air bleed size. I tested with .025, .035 and .045 bleeds. I even took the bleed out and it was still within that 100 rpm. My test could be flawed. If it is someone please point out my error. Also maybe someone could try to repeat this test on their motor and report back with their results. I'm starting to think that the main air bleed isn't the cork in the bottle when it comes to booster startup. I attached a photo of my results. please excuse the sloppy writing.
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20230104_221640.jpg
 
Click to expand in the previous post to see the text of my response. I somehow put my response in the quote.
 
I'm not sure but the straw analogy might be over simplified for booster startup point measured in rpm.
 
92b said:
I'm not sure but the straw analogy might be over simplified for booster startup point measured in rpm.
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To me, the straw analogy is about WOT. If pressures equalize, flow will stop. A large air bleed will lean out WOT due to the pressure it exposes because of its size. I do not believe this is the case when starting the booster though due to air speed and pressures a little throttle blade opening.
 
I think the straw analogy works if you have a kill bleed larger than the main air bleed and an emultion package that has no holes that are above the fuel level prior to booster startup. Maybe.
 
Another thought about your dyno test, is what Mattax posted in the vacuum advance myth section, maybe it needs to be a higher load during your test?? Guessing here. Idle is surprisingly high load, and before emissions concerns, fairly rich. The engine is producing very little torque at 500 or even 600 rpm. A percentage of that goes to overcoming friction. So best to think of it as a high load, somewhat rich and dense situation.
 
Bewy said:
RB/TT5,

I have posted TWO quotes, one from Holley engineer Mike Urich & one from Dave Emanuel's Carter book that state that a smaller MAB starts the system sooner. That part of it is simple high school physics, as shown with the straw example.

Despite all the blustering & hoo-ha from RB, nobody, repeat nobody, has reproduced or linked a statement to Shrinker/Tuner that states a bigger MAB starts the main system sooner.
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Once again, it WAS posted. And you didn’t like it. I have asked Tuner several times (on the phone and in person) if I was reading the above quote correctly in that a bigger MAB starting the mains sooner.

And every time he says the same thing. And that is I’m reading and understanding it correctly.

Its your issue, not mine.
 
92b said:
View attachment 1716030763
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Did you get you numbers on a flow bench or on the car?

I remember reading about the SB2 head. Or maybe it was the SB2.2 head. It was one of them.

Anyway, the discussion was about why the passenger front booster always started sooner than the other boosters.

IIRC, no one had an answer for it and again IIRC, they just lived with it. I asked if it did the same with a 2X4 set up and I don’t think anyone said one way or the other.

So there may be some conditions where the bigger MAB could delay booster start up but as a general rule (as in most of the time) a bigger MAB will start the mains sooner.

It appears that some think that because a bleed has a certain characteristic at high air flows it behaves the same at low air flows.

That means they are excluding pressure differentials across the bleed, booster and fuel bowl vent.
 
Rat Bastid said:
It appears that some think that because a bleed has a certain characteristic at high air flows it behaves the same at low air flows.

That means they are excluding pressure differentials across the bleed, booster and fuel bowl vent.
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It also means they are excluding/ ignoring fuel flow characteristics when air is introduced
 
@92b Its great to see some testing. What 750 dp was your test conducted with? Main bodies? Metering blocks? Emulsion pack?
 
FWIW: because I'm by no means the sharpest crayon in the box, and am barely keeping up in this thread. I've purchased a Gopro type camera. The plan is to make a mount that I hope will allow me to video the boosters in real world driving conditions. I plan to somehow incorporate a tachometer in the view. Also plan to make a mount for an additional camera in the car to monitor gauges. Then hopefully learn how to edit and sync. both videos to show what happening and when. Because I understand better by doing than reading. Hope to gain a better understanding for my own personal knowledge.
 
MomsDuster said:
FWIW: because I'm by no means the sharpest crayon in the box, and am barely keeping up in this thread. I've purchased a Gopro type camera. The plan is to make a mount that I hope will allow me to video the boosters in real world driving conditions. I plan to somehow incorporate a tachometer in the view. Also plan to make a mount for an additional camera in the car to monitor gauges. Then hopefully learn how to edit and sync. both videos to show what happening and when. Because I understand better by doing than reading. Hope to gain a better understanding for my own personal knowledge.
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That's awesome Mark. Thank you. I know standing next to my car and slowly increasing throttle, at about 2700-3000rpm I can watch fuel erratically flowing the to the booster and get misses. It is thought it is a rich miss. I have made some carb adjustments and will try this again. You will have it on "film" with corresponding gauge readings. I am very interested in seeing what you have going on. I know annular boosters are more sensitive and respond quicker/differently than other boosters.
 
92b said:
I think the straw analogy works if you have a kill bleed larger than the main air bleed and an emultion package that has no holes that are above the fuel level prior to booster startup. Maybe.
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I might be wrong about the kill bleed . I have to look and see where that vents.
 
This post by Tuner on speed talk, for me sums up this entire conversation.

“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.”
 
71GSSDemon said:
Another thought about your dyno test, is what Mattax posted in the vacuum advance myth section, maybe it needs to be a higher load during your test?? Guessing here. Idle is surprisingly high load, and before emissions concerns, fairly rich. The engine is producing very little torque at 500 or even 600 rpm. A percentage of that goes to overcoming friction. So best to think of it as a high load, somewhat rich and dense situation.
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What I did was look up the power @50 mph on my chassis dyno. You can see those numbers on the picture of the chart I posted. I put hp numbers next to a couple of torqe numbers for reference. I think a 73 charger was 15 hp @50mph. I'm just taking Mustang dynos word for that. I think the loads I used should be close to cruising.
 
Rat Bastid said:
Did you get you numbers on a flow bench or on the car?

I remember reading about the SB2 head. Or maybe it was the SB2.2 head. It was one of them.

Anyway, the discussion was about why the passenger front booster always started sooner than the other boosters.

IIRC, no one had an answer for it and again IIRC, they just lived with it. I asked if it did the same with a 2X4 set up and I don’t think anyone said one way or the other.

So there may be some conditions where the bigger MAB could delay booster start up but as a general rule (as in most of the time) a bigger MAB will start the mains sooner.

It appears that some think that because a bleed has a certain characteristic at high air flows it behaves the same at low air flows.

That means they are excluding pressure differentials across the bleed, booster and fuel bowl vent.
Click to expand...
I did this on the engine dyno.
 
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