Emulsion Part 2

[Walter R. Malik]

A slide carburetor is a whole lot different than a butterfly carburetor.
With the slide you are always changing the area of the venturi throughout its travel.

True. But does the analogy fit?

Apples and oranges are both fruit ... the only working similarity between those carburetors is they both mix metered fuel with air; going about it all differently.

The emulsion section of those carbs is usually an extension of the main jet holder.
That needle, varies the size of the conduit, (similar to the booster passage), from where emulsified fuel mixture enters the airstream and is profiled to match the ever changing venturi characteristics.

[jmarkaudio]

Any takers?

Where do you want it to go turbulent?

Hysteric

Do you want it to go turbulent? What you do not want is it to hit the transition area between Laminar and Turbulent in the area where the most load is seen.

Walter hit it, you want it to be enough to not be a significant restriction to fuel flow, to do this it must be larger than the main jet. With a downleg keeping the size from going too big and making flow through the booster too slow is important as well. What I see typically with 4150's on gas is .040" to .060" larger than the main jet with a downleg. I have seen more, a 4781 850 is about .080" more, with methanol some 4150's may get under .040", as .190 is the maximum safe passage size. With a downleg I like to see around .050 from what I think is the target jet will be. I think the 850 may have been better suited with around .160, as at .180 I can get plenty of E85 through the stock booster.

Dominators with annulars are typically .030 to .060 larger than the target jet size, a .160 to .170 booster pin and banjo passage will cover gas from a 1050 to 1250. E85 will run from .180 to .200 in those carb ranges, methanol from .200 up to the maximum diameter you can get a methanol pin, somewhere around .218 to .224. This is part of the issue with getting sufficient fuel through a Dominator on methanol, there just isn't enough material in the banjo and booster pins to go any larger. There are other ways to add fuel, and with more resources ($$$) there are some other possibilities. Braswell has a booster banjo and pin for their large format carbs that has a .250 passage, and with some work could be adapted to a Holley.

Someone made the comment on mainwells, the mainwell itself is usually capable of passing enough fuel, and also needs to be larger than the jet. Most are tapered, although I'm not convinced it needs to be. Taper in the stock metering blocks was there to allow the die casting pins to be extracted, without a minimum taper the pins would get stuck. Gas blocks are typically a #2 taper, roughly around .165 at the bottom and .190 at the angle channel. 3 circuity blocks with an idle tube are usually a #3 taper, around .185 at the bottom and .210 at the angle channel. Methanol blocks vary depending on the builder, the minimum on a 4150 I have seen is the #3 taper, most are at or over .200. E85 varies from a #2 up to a methanol passage depending on the size of the carb.

Angle channels I try to make just a little smaller than the booster passage, so that turbulence is minimized at the entrance to the booster.

[jmarkaudio]

One more thing, if the booster passage is too small it becomes a restriction point, this will disturb the effect of the emulsion system. Balancing the sizes is important to the correct operation of the carb.

[USMC_Spike]

So, what I don't understand is why the praise for the annular booster, which atomizes better then
then stock venturi...But the annulars ae large diameter so the signal is different yes?
What is the difference? someone please explain.

Then when you get to it and want o place it in your carb and get t he benefits from it...
it deosent do so well. Why? Why not? Help, what is going on with these.

Has the whole industry just let the annular market just be for the larger blow through
carbs, wth large diameter venturis....

Why not come out with some small diameter ANNULAR venturis that will work and flow properly with smaller carbs (maybe)_ or at least largers cabs but that will work out ok.

Why isn't it being done?

AND

I"m not a Braino, so please someone, sit me down and just 'splain it to me.

cheers,

Spike

[raceman14]

Spike,
The larger surface area and greater ratio of distribution holes in the annular ring of the booster when compared to one big hole in a downleg is what I have found to make the difference. I do things way different with my annular stuff than most folks but I shoot for maximum hp and really don't care about flat fuel curve or stoichiometric perfection...

Working on an acceleration based Superflow ChassisDYno has also taught me that it is equally as important to address the fuel burn curve of what fuel u are running as well as the spiark curve to maximize that same burn with the combustion chamber u are running.

I have found there is as much as 30-40RWHp in optimizing the fuel type, to engine type, to fuel curve and ignition curve, and while doing this all of this needs to be optimized for the acceleration curve of the drivetrain of ur vehicle.

I tell most racers it is like 5-Dimensional Chess, with all planes moving in their own plane as time and temperature changes.

In simple terms I make small incremental changes with only concern to increasing acceleration rate of the engine and of the 3800# wheel. After about 10 good changes you can start seeing 20-30 RWHP.

Not saying my way is the only way, it is just the on I use.

There is some good learning in studying the old Chrysler lean burn high timing engine control system. The fact that it did not work does not mean it was not good work.

[rabbit]

Walter hit it, you want it to be enough to not be a significant restriction to fuel flow, to do this it must be larger than the main jet. With a downleg keeping the size from going too big and making flow through the booster too slow is important as well. What I see typically with 4150's on gas is .040" to .060" larger than the main jet with a downleg. I have seen more, a 4781 850 is about .080" more, with methanol some 4150's may get under .040", as .190 is the maximum safe passage size. With a downleg I like to see around .050 from what I think is the target jet will be. I think the 850 may have been better suited with around .160, as at .180 I can get plenty of E85 through the stock booster.

Interesting, thanks for the explanation.

[Walter R. Malik]

Why not come out with some small diameter ANNULAR venturis that will work and flow properly with smaller carbs (maybe)_ or at least largers cabs but that will work out ok.

Why isn't it being done?

AND

I"m not a Braino, so please someone, sit me down and just 'splain it to me.

cheers,

Spike

There ARE boosters in the marketplace ... have you looked at the primary booster in the Holley "Truck Avenger" carbs; It is a regular Holley diameter "annular" booster.

As I have previously mentioned a Braswell diameter, downleg "annular" booster is manufactured by "Stealth Racing Carburetors". This stuff is not inexpensive however, it certainly IS available.

Annular boosters, presuming the same outside diameter, have more signal gain at "pullover" and don't increase a whole lot where with a regular booster the gain keeps increasing at a greater rate than an annular booster as total airflow increases. They have different signal curves ALONG with the annular booster providing a smaller droplet size.

[PRO SYSTEMS]

USMC SPIKE RE: Small diameter annulars - We were testing this concept for a set of Pro Stock carbs many years ago for Dodge.

We first tried it on 4150 carbs and built several different small 4150 series annular boosters that mounted inside the hoop of a dog leg booster.

What we found in engines with high rates of acceleration (video taped it to see what was happening) is that the tighter turns required for the fuel to get out and into the air stream created a lean condition when we would shock it to simulate a launch on the wet flow bench (similar to a transbrake). At first the fuel would only come out of the nearest side then it would fill the hoop.

The wider annular boosters do not have such tight turn radii so as a result we didnt see the same issue, the larger radii booster filled up the area quickly. We found it was better to run a larger venturi with the larger size annular booster than a smaller venturi and the small annular booster at the same achieved cfm rating.

So as a result, we abandoned the concept for use on Dominators as we assumed the same thing would result there as well. But since we had the 4150 built we tested it on track...it did the same thing there. It was lean on launch but once it filled the hoop it was ok, but nothing you wanted to spend any further development dollars toward.

The less turns (tightness of turns) and gyrations that the fuel encounters, the quicker you are going to shift recover and launch. Hence the simplicity of the booster on the SV1. So even in a failure you learn something.

Patrick James
PRO SYSTEMS

[Walter R. Malik]

USMC SPIKE RE: Small diameter annulars - We were testing this concept for a set of Pro Stock carbs many years ago for Dodge.

We first tried it on 4150 carbs and built several different small 4150 series annular boosters that mounted inside the hoop of a dog leg booster.

What we found in engines with high rates of acceleration (video taped it to see what was happening) is that the tighter turns required for the fuel to get out and into the air stream created a lean condition when we would shock it to simulate a launch on the wet flow bench (similar to a transbrake). At first the fuel would only come out of the nearest side then it would fill the hoop.

Patrick James
PRO SYSTEMS

To a point, this is true for a DRAG racer however, the phenomena can be greatly reduced by being sure that one of the holes withing the annular ring is slightly larger and directly in-line with the booster leg.

[levisnteeshirt]

I think what has to be kept in perspective is the speed of vaccum in the passage ,, and your not going to force the engine to draw more fuel than it really wants , you can to a point , but at what point is it beneficial ? If the carb your dealing with is smaller than what the engine really needs , then the added emulsion air helps cure an over rich condition. If you have plenty of time to experiment on a dyno to see IF any emulsion changes results in a more attractive fuel curve/ torque / hp ,, then go at it . I think all of this came from Nascar that has limitless testing available to them , but its not that practical in every day situations.

Anyway ,, this is the only explantion I have for how well the old 2 emulsion hole blocks work when you take billet or HP metering blocks off and put them on. They made the main well deeper , but added emulsion holes that have to lift it farther ? Lowered the PVCR so it hits the main well at a lower point , I would imagine this is to have a greater effect of the head pressure from fuel in the bowl to enhance the lift of the fuel higher in the main well ?? It has to change direction at this lowered point from the power valve inlet. Thats not good ,,

i think its the wrong direction IMO. The fuel should shear once its hits the air stream and vacuum in the booster and atomize , then its going to do this even more in the cylinder ,, the carb can only do so much and not more than its able to help the whole process IMO

[PRO SYSTEMS]

Walter, we messed with that, but what you actually wanted to do was have the hole inline smaller so that the fuel would go around the channel to fill the other side faster. It then made it kick more fuel to that far side after it filled the hoop, so that was a no go. Then we messed with channel size and offsetting the ledge and even bleed bypasses in the booster...it was just a dead end. But very educational.

Patrick James
PRO SYSTEMS

[Walter R. Malik]

Walter, we messed with that, but what you actually wanted to do was have the hole inline smaller so that the fuel would go around the channel to fill the other side faster. It then made it kick more fuel to that far side after it filled the hoop, so that was a no go. Then we messed with channel size and offsetting the ledge and even bleed bypasses in the booster...it was just a dead end. But very educational.

Patrick James
PRO SYSTEMS

The bigger hole "in-line" will certainly make the annulus fill slower but, that larger amount of immediate fuel tends to cover-up a lot of the lean point.
We discovered this on a #6425 annular "venturi" 2 barrel carb however, the condition might be a lot different with a booster having a much shorter length annulus to fill. The angle INTO the annulus was something I never thought about,
Geometrically, the smaller O.D. annulus would have less of an angle where the edge of the feed conduit diameter intersects.

As with most carburetor stuff ... it is ALL application specific.

[jmarkaudio]

What I have seen on a flow bench is that the smaller ID boosters have a lower booster signal, I have pulled from 1" of water and still it has a better signal when the ID is larger. The larger ID has more air flow through it, so it has a better signal AND flows more air through it. What this allows is a large carb to have sufficient signal to meter with. So unless the fuel is already being over atomized from a restricted carb size/high engine vacuum at WOT, I don't see any reason to run a smaller booster. Even on a larger 4150 the airflow loss with an standard annular isn't a lot.

[Walter R. Malik]

What I have seen on a flow bench is that the smaller ID boosters have a lower booster signal.
So unless the fuel is already being over atomized from a restricted carb size/high engine vacuum at WOT, I don't see any reason to run a smaller booster.

Exactly ... the thing with booster signal though, is that once you have an adequate amount, more is not beneficial; even detrimental in some cases.

In my opinion, The smaller diameter annular boosters are more about droplet size and the signal increase curve rather than absolute signal strength; that is what I have seen.

Like most carburetor things ... helps in some instances, hurts in others and just makes little performance difference in the rest.

[jmarkaudio]

I have not found a detriment to more booster signal in a non restricted application. Higher signal also creates a higher pressure differential for the fuel leaving the booster, it allows a larger carb to be used as well as passing more air through the larger hole for a given pressure drop.