Ultra XP850 Almost there!

[Ironmike]

I guess this is really a follow up from a post I made last year. Was running really rich at any cruise speed and ok at WOT. Took everyone's advice and did some surgery. Here's what I did and where I am now.

The T-slot restrictors from factory where huge. I have them at .062 now, all four corners. That helped a lot. Was a little lean during brisk acceleration(front barrels only). So... next I opened up the power valve restrictors up front to .077. I run 2 4.5 power valves. Helped a bit.

Next I put on a 1/2 inch HVHS Supersucker and drove it around for about a hour today. Plugs look exactly like I would want ..............on the passenger bank. Drivers side maybe a bit too lean. Almost new looking.

At WOT, it's hard to watch the A/F gauge but I got a glimpse of it and it appears lean-ish. 2nd gear nearing redline(6800) I saw 14 to 1. BUT again, that thing will rev so friggin fast I'm on the rev limiter in the blink of an eye.

So now I am much better cruising(13ish to 1) but not perfect. WOT a bit lean. Drivers side leaner that pass side.

Here's the set up: 78 jets up front. 86 in the back
37 MAB's up front. 34 in the back
And the real kicker is 4.5 P valves both up front AND in the back. I know with P valves your jetting should be square, but that aint gonna work

I'm thinking I should open up the secondary PVRC as I did with the front. That should get me richer at WOT. ......i think.

How can I get the passenger bank a bit more fuel, without enrichening my cruise AFR?

Smaller MAB on that side? Bigger jet on that side? Sounds crazy, but I saw Holdener do it on the dyno once.


I have done nothing to the emulsion circuit on the metering blocks, which are many. It's ridiculous that Holley did that, but I have no clue how to correct it, if it even needs correcting.


So, this is a lot to digest, I know, but I'm sooo close!

 

[PROSTOCKTOM]

Increase your jet size on the drivers side only to richen that side up.

Tom

 

[Newbomb Turk]

I guess this is really a follow up from a post I made last year. Was running really rich at any cruise speed and ok at WOT. Took everyone's advice and did some surgery. Here's what I did and where I am now.

The T-slot restrictors from factory where huge. I have them at .062 now, all four corners. That helped a lot. Was a little lean during brisk acceleration(front barrels only). So... next I opened up the power valve restrictors up front to .077. I run 2 4.5 power valves. Helped a bit.

Next I put on a 1/2 inch HVHS Supersucker and drove it around for about a hour today. Plugs look exactly like I would want ..............on the passenger bank. Drivers side maybe a bit too lean. Almost new looking.

At WOT, it's hard to watch the A/F gauge but I got a glimpse of it and it appears lean-ish. 2nd gear nearing redline(6800) I saw 14 to 1. BUT again, that thing will rev so friggin fast I'm on the rev limiter in the blink of an eye.

So now I am much better cruising(13ish to 1) but not perfect. WOT a bit lean. Drivers side leaner that pass side.

Here's the set up: 78 jets up front. 86 in the back
37 MAB's up front. 34 in the back
And the real kicker is 4.5 P valves both up front AND in the back. I know with P valves your jetting should be square, but that aint gonna work

I'm thinking I should open up the secondary PVRC as I did with the front. That should get me richer at WOT. ......i think.

How can I get the passenger bank a bit more fuel, without enrichening my cruise AFR?

Smaller MAB on that side? Bigger jet on that side? Sounds crazy, but I saw Holdener do it on the dyno once.


I have done nothing to the emulsion circuit on the metering blocks, which are many. It's ridiculous that Holley did that, but I have no clue how to correct it, if it even needs correcting.


So, this is a lot to digest, I know, but I'm sooo close!

The first thing I’d do is get rid of those huge MAB’s. That’s one reason why your jets are so big plus the power valves.

Thats also why it runs better with late opening power valves. You are starting the booster way too soon with those huge MAB’s.

I start at .026 and never go over .030 and I don’t like doing that.

With a good booster I can use something like an .022-.023 MAB.

That’s just too much MAB.

 

[TT5.9mag]

Tell us what the emulsion is currently. It’s probably all 5 huge like every billet block has these days. You’ll likely end up at 3 holes per block. The intake has more to do with distribution bank to bank than the carb but you absolutely can jet one side richer or leaner and see if it helps.

 

[Ironmike]

The first thing I’d do is get rid of those huge MAB’s. That’s one reason why your jets are so big plus the power valves.

Thats also why it runs better with late opening power valves. You are starting the booster way too soon with those huge MAB’s.

I start at .026 and never go over .030 and I don’t like doing that.

With a good booster I can use something like an .022-.023 MAB.

That’s just too much MAB.

wait a minute. I thought smaller bleeds increases fuel flow by starting the booster sooner.........

Says in my Holley book smaller bleeds increase fuel/ richer. Do I have it wrong?

I have run smaller bleeds, but man if i went to .026's, I'd have 60 something jets in all the way around. Not sounding right for a 600-ish HP smallblock.

But i will listen to your explanation.

 

[Newbomb Turk]

wait a minute. I thought smaller bleeds increases fuel flow by starting the booster sooner.........

Says in my Holley book smaller bleeds increase fuel/ richer. Do I have it wrong?

I have run smaller bleeds, but man if i went to .026's, I'd have 60 something jets in all the way around. Not sounding right for a 600-ish HP smallblock.

But i will listen to your explanation.

If that’s what the book says, it’s wrong. I’m not sure what book you have but the two volume Taylor books cover this. So do Obert and Larew.

The main air bleed affects both ends of the fuel curve, but it affects both ends differently.

At low air flow (before the booster starts) the MAB acts like an emulsion bleed and at high air flows (after the booster starts) it acts like an air bleed.

So…at low air flow the bigger MAB makes the fuel in the main well lighter, so it starts the booster sooner and at high air flow the bigger bleed kills more signal, making the fuel curve leaner at WOT.

At low air flow the smaller MAB is letting less air into the main well so the fuel is heavier and that delays the start of the booster. Once the booster starts, the smaller air bleed doesn’t kill the signal as much, making the fuel curve richer at WOT.

If you think of the fuel curve as a flat line (you have to picture this in your mind until I do a video on this) from idle to wide open throttle. The X axis is lean/rich with lean at the top and rich at the bottom. The Y axis is idle to WOT, left to right.

And let’s say that stoichometric (14.7:1) is the middle of the graph and the straight line is on 14.7:1 from idle to WOT.

We know the engine won’t want that straight fuel curve so we have to tune it. Let’s ignore idle tuning, emulsion and main jetting and just look at the MAB.

Let’s say with a .026 MAB the line on the graph at idle through 2200ish is lean (you are on the T slots at a part throttle cruise) and then you open the throttle and at 2500 it starts to go rich because the booster started. Now you are on the main jet and whatever the A/F ratio is, it is until the .026 main air bleed doesn’t bleed off as much signal and it goes rich at say…5500.

Let’s use the same numbers except we use your .037 MAB. Now instead of the fuel curve being lean to about 2200, the bigger MAB is making the fuel in the main well lighter, so it’s easier to get to the booster. So instead of the booster starting at 2500, now it’s starting at 2000. Of course at 5500 on the same main jet it’s leaner because the bigger MAB is bleeding off more signal.

So the smaller MAB delays the start of the booster because the fuel in the main well has less air, is heavier and can’t move as easily up the well to the booster. That makes the bottom of the fuel curve leaner because you have less overlap between the T slots and the main jets.

The bigger MAB makes the fuel in the well lighter, so it’s easier gets to the booster easier and starts the booster sooner so now you have more overlap with the T slots and the fuel curve is richer.

So the book is wrong. You need to cut the MAB on both sides down to .026, get rid of the secondary power valve (you don’t need it because you do not cruise on the secondary main jets like you do the primary main jets), leave your main jets where you have them. Make sure you only have two emulsion holes open. They only need to be between .026-.028 for down leg boosters. If you have 4 emulsion blocks, you usually start tuning with 1-3 open and 2-4 blocked. I’ve had to use 2-3 open and 1-4 blocked depending on booster signal but you have to test for that.

If you have 5 emulsion blocks 1-3-5 are blocked and 2-4 are open to start.

If you have 3 emulsion blocks 1-3 are open and 2 is blocked to start tuning.

If you are going to tune emulsion you need to think of the fuel as a spring, or even a slinky. It’s elastic. If you want to make any part of the fuel curve richer you can open the emulsion up. The top of the emulsion stack is idle and the bottom is WOT.

You use emulsion to fine tune the fuel curve. Adding air makes that part of the fuel curve richer. Taking away air makes the fuel curve leaner.

On some of my tunnel ram stuff (and one single 4 I can think of) only have one emulsion hole open. The booster signal is so good it doesn’t need any help pulling fuel.

That’s a brief, simple explanation of how the MAB affects the system.

A bigger main air bleed makes the fuel curve richer at low air flow (because the booster starts sooner) and leaner at high air flow because it bleeds off more signal.

A smaller main air bleed makes he fuel curve leaner at low air flow (because it delays the start of the booster) and richer at higher air flow because it bleeds off less signal.

Edit for the fourth time lol: NACA number 49 covers this and has some graphs. If we ask @Mattax real nice he can post some of those graphs because they help visualize what’s happening.

You can download the paper. It’s worth reading.

 

[TT5.9mag]

@Newbomb Turk have you noticed the emulsion tuning being that deliberate? IE top-idle and bottom-WOT. Sometimes it does what you explained and sometimes I feel like it doesn’t do much at all. Maybe it’s related to the carb size and cu/in (signal) relationship or how much power the engine makes. Great post btw.

 

[Newbomb Turk]

@Newbomb Turk have you noticed the emulsion tuning being that deliberate? IE top-idle and bottom-WOT. Sometimes it does what you explained and sometimes I feel like it doesn’t do much at all. Maybe it’s related to the carb size and cu/in (signal) relationship or how much power the engine makes. Great post btw.

That’s true. Sometimes it isnt that clearly defined. I’m not sure why.

For the most part, that’s how the changes should work but, like I said the fuel in the main well is like a slinky.

Now that I think about it even the kill bleed has some influence on the emulsion stack and I’m not clear on why that is. I personally have never had to change the kill bleed size but I know guys who have had to do it.

It may also be in the relationship to how big the MAB is, how many and how big the emulsion holes are and booster signal.

At this point any carb I’m building is getting annular boosters because the signal is so much better. And especially on pump gas carbs.

Pump gas is blended for EFI do the distillation curve, RVP and all that stuff is blended for EFI. Using even the best downleg booster the fuel isn’t atomized nearly enough.

And since most guys are using a cold air intake (air gap style) there is far less heat to vaporize the fuel. You end up running a bigger main jet just to get enough vaporized fuel in the chamber to get all of the oxygen paired up with the fuel.

Of course, you have all that extra fuel and eventually it does burn but it’s so late all it does is drive up the EGT and makes zero power.

You can’t always see this on the plugs, but you can see it with EGT. If you don’t or can’t measure EGT you can pop the header off and look at the exhaust port.

It will be wet with partially burned fuel, and it will be gooey and sticky. And it can quite thick. That’s a big tell you have issues getting the fuel vaporized before the plug goes off. I’ve had aluminum heads come in that were so dirty we couldn’t get them clean.

A paper roll would just gum up with it, so I’d take a used burr I didn’t care much about and grind it out of there.

Also, you find that sometimes in that situation guys are running a range or two hotter plug than what you might think it should be. Thats because all that extra fuel isn’t atomized cooling the plug. And they start fouling plugs.

So they use a hotter plug to stop that. It’s a bandaid but at least it’s not fouling plugs.

Edit:I am reading a book on ballistics and in the background my mind was covering emulsion and why it behaves like it does, and that the fuel in the main well acts like a spring.

The forces that act on the main well go both ways. I other words, as the low pressure area at the booster is lower than the main well, the fuel column moves up the main well to the booster and into the cylinder.

This is all good except for the dirty little variable of reversion. It also works on the booster, but in reverse.

If the booster sees high pressure under it from a reversion pulse, two things occur.

1. The fuel will move back up into the main well and compressing what’s already in there. Obviously when the high pressure is removed and the fuel changes direction and heads back up the main well and to the booster.

2. Some of that reversion pulse will force air and fuel back up through the booster the wrong direction. The booster is dumb and only knows pressure differential. When that happens, it picks up more fuel on the way past the booster the wrong direction. You now have essentially double the fuel through the booster minus what backed up into the main well.

Once the pressure differential changes back to the “normal” direction it picks up fuel again, for the third time. You now have a seriously rich condition that is made worse by the EGR gases from the reversion pulse itself.

This is one reason (I believe) that the emulsion circuit sometimes doesn’t behave as we think it should. Reversion is affecting the booster and by consequence the main well. In fact, reversion can be so bad it will shut the booster off and no fuel will flow through it until the reversion is changed by changing rpm, load or both.

Which is why I try to get guys to consider almost ANYTHING that will reduce reversion pulses in the intake tract.

That can be steeper than orthodox valve seat angles. I reverse flowed almost every port I did when I had my flow bench. You start to see traits develop, especially with a lot of overlap.

Not back cutting the valves if you find the port is flowing too well in reverse.

The use of anti reversion plates. This is a big one. Most don’t see the expected results because to get a true anti reversion plate to function you have to modify the intake manifold flange. If you don’t do that, they don’t work.

Proper runner taper is a big deal. It’s hard to control in a single 4 manifold but you do what you can.

That’s my quick thoughts on why the emulsion system doesnt behave as we think it should at times.

Back to my ballistics book…

 

[Ironmike]

OK Turk. I'm going to try it. BUT I'm guessing I'm gonna be really rich at cruise RPM and really lean at WOT(without the rear P valve)...........keeping the same jetting as you suggested. As far as emulsions, I may leave those alone at first. don't want too many changes at once.

I was hesitant last year to muck around with my T slots, but I did it and you were right. Big improvements.

I'm hoping it's like slalom skiing on water. It just don't make sense pulling hard across that wake until you finally do it. THEN it all makes sense at once!

Let you guys know how it turns out, good or bad.

I almost forgot. This is right out of the paperwork that came with my carb. You can understand why I just don't get it. Yet. Read the underlined part.

 

[Newbomb Turk]

OK Turk. I'm going to try it. BUT I'm guessing I'm gonna be really rich at cruise RPM and really lean at WOT(without the rear P valve)...........keeping the same jetting as you suggested. As far as emulsions, I may leave those alone at first. don't want too many changes at once.

I was hesitant last year to muck around with my T slots, but I did it and you were right. Big improvements.

I'm hoping it's like slalom skiing on water. It just don't make sense pulling hard across that wake until you finally do it. THEN it all makes sense at once!

Let you guys know how it turns out, good or bad.

I almost forgot. This is right out of the paperwork that came with my carb. You can understand why I just don't get it. Yet. Read the underlined part.

View attachment 1716410406

Ok, last things first. The instructions say that because they never consider what happens at low air flow and they are just talking about what the MAB does at high air flow.

Now let’s talk about the rest of it.

When you reduce the size of the main air bleed you will start the booster at a later rpm than it is starting now. That will make the bottom of the fuel curve leaner because you are on the T slot without having the booster start. There needs to be some overlap between the T slot and the booster starting (when you actually start pulling fuel through the main jets) but most guys have too much overlap. So you are still in the rich part of the T slot and the booster is adding fuel and it’s rich down low.

So you should be leaner at a cruise just on the T slots. Of course when the booster does start (hopefully around 2500ish) you will be at the tail end of the T slot adding fuel and you will then cruise just on the primary main jets.

You need to tune the cruise for when you are just on the T slots by playing with the T slot restricters. Once you get that happy then you tune for cruise on the primary main jets.

You want to run the smallest primary main jet that doesn’t give a lean surge on as flat and level ground as you can find. So tune it for a touch of surge, then add two main jet sizes and don’t touch those again. You don’t tune WOT with the primary main jet.

At this point you can see why getting the power valve open at the right time is so critical. You’ve got your T slot cruise all dialed in and you’ve got your cruise on the primary main jets all nice and crispy. If you touch the throttle the PV needs to open soon enough so that it is adding fuel to cover the lean spot along with the accelerator pump.

Most guys find you can run a much smaller pump nozzle when everything else is correctly tuned. That saves fuel by not pumping all that extra fuel you only need because the rest of the tune is off.

So pay attention to what your manifold vacuum is while you are cruising on the main jets and then try to be 2-4 inches below that point to open the PV.

If you cruise at 15 inches the best you can do is a 10.5 PV but IIRC @RustyRatRod posted a link to someone selling 12.5 PV’s so that may be worth looking into.

After all that you can start tuning for WOT.

You should not need the secondary power valve because the much smaller MAB, now doing its job at high air flow will not bleed off as much signal as the bigger MAB and it will naturally be richer. Remember a smaller MAB makes the bottom of the fuel curve leaner because it delays the start of the booster and makes the top of the fuel curve fatter because it’s not bleeding off as much signal.

When you tune for WOT always tune the primary side by changing the size of the PVCR and NEVER the primary main jet once you’ve got your cruise all dialed in. If you change the primary main jet to add fuel at WOT you will now make the engine fat at a cruise wen you had it already nailed.

So any changes to the WOT fuel curve on the primary side is done with the PVCR’s and not the primary main jets.

You can figure the area of the PVCR and the primary main jet to get you close to what you’ll need for a secondary main jet.

Normally it’s a 6-10 split depending on the rest of your calibrations.

It’s that easy.

You’ll burn less fuel, make more power, have cleaner oil and have more fun driving it when you get the carb dialed in all good and toasty.

It just takes a bit of work but in the end it’s worth it.

 

[TT5.9mag]

@Newbomb Turk you’re writing AJ style posts except they're full of useful information. Thanks. I never even once considered what reversion would do to the booster and the effect that would have on the fuel in the main well. I know what I’ll be thinking about tonight when I’m trying to sleep.

 

[Ironmike]

it's starting to make sense to me. Except the Power valve stuff. At idle 1150RPM i'm only making 11 inches of vacuum. I have no idea where it is at cruise. Maybe I'll pick up a long piece of hose and bring the gauge in the car to check that.

Also, I'm usually over 2500 at cruise. 4.30 gears. I know 60 MPH is around 3100 RPM.

Anxious to try the smaller MAB's. Have to order those. Have 31's all the way up to 40.

 

[Newbomb Turk]

it's starting to make sense to me. Except the Power valve stuff. At idle 1150RPM i'm only making 11 inches of vacuum. I have no idea where it is at cruise. Maybe I'll pick up a long piece of hose and bring the gauge in the car to check that.

Also, I'm usually over 2500 at cruise. 4.30 gears. I know 60 MPH is around 3100 RPM.

Anxious to try the smaller MAB's. Have to order those. Have 31's all the way up to 40.

.026 would be far better than .031 especially if your cruise rpm is that high.

For the power valve, the tuning lie (it now can no longer be considered an error because it’s been proven an error for so long that if guys are still teaching it wrong they are just lying but I digress) of using half idle vacuum is wrong.

It always was wrong and in a few very limited situations it’s always wrong.

The power valve can be wide open at idle and it will not flow any fuel. ZERO.

That’s because it feeds through the booster when it adds fuel under load. If the booster isn’t started, the power valve can be wide open and it won’t affect anything.

There are a couple of exceptions to that that come to mind.

One is the blown power valve. This was an issue from the days of when Colt industries bought Holley. They made some power valves on worn out tooling or something that caused them to fail like that.

It is rare now.

The other is the power valve hitting the back of the cavity it sits in.

This holds the metering block away from the main body and causes a leak. The power valve gets blamed but it’s really a casting issue.

Every carb should be checked for this. Simply take the gasket off the metering block and with the power valve installed normally set the metering block on the main body.

It should sit flush. You will know if the power valve is hitting with that test. If it is, simply grind some clearance in the bolt boss or whatever it’s hitting until it doesn’t hit.

 

[Bewy]

Mike,
The Holley info in post #9 is correct. Holley knows how their carbs work.....& other venturi carbs work the same way. With no air flow through the venturiis, the fuel in the main well is the same as the fuel level in the float bowl [ actually, slightly lower because the idle fuel is drawn from the main well ]. If you look at the sight plugs in the fuel bowl, you will see that the fuel level [ bottom of the the threads ] is about 1/4-3/8" lower than the booster entrance on the main body [ this is called the spill height ]. The fuel in the well has to be lifted before it can enter the booster. The air bleed [ AB ] bleeds off some of the depression at the booster, where the suction [ vacuum ] is being applied. The depression/suction is created by the air flow past the booster. With a bigger AB, more suction is lost & more air speed [ rpm ] is reqd to build up enough suction to initiate flow. Small AB starts the main system earlier, & vice versa.

 

[Newbomb Turk]

Mike,
The Holley info in post #9 is correct. Holley knows how their carbs work.....& other venturi carbs work the same way. With no air flow through the venturiis, the fuel in the main well is the same as the fuel level in the float bowl [ actually, slightly lower because the idle fuel is drawn from the main well ]. If you look at the sight plugs in the fuel bowl, you will see that the fuel level [ bottom of the the threads ] is about 1/4-3/8" lower than the booster entrance on the main body [ this is called the spill height ]. The fuel in the well has to be lifted before it can enter the booster. The air bleed [ AB ] bleeds off some of the depression at the booster, where the suction [ vacuum ] is being applied. The depression/suction is created by the air flow past the booster. With a bigger AB, more suction is lost & more air speed [ rpm ] is reqd to build up enough suction to initiate flow. Small AB starts the main system earlier, & vice versa.

View attachment 1716410967

lol. Your ignorance contributes to the holleyitius you ***** about.

The information is WRONG. At best it’s half right.

It’s funny how easy it is to test this and learn how wrong you are.

In the end, Mike will learn who is full of ****.

 

[Ironmike]

uh oh. Simma down now!
Bleeds are coming tomorrow.

 

[Bewy]

Somehow, I do not think all these people can be wrong....[ below ]. The last link is from the late John Passini, who wrote several books on carburation. He was English, hence some of the quaint phrases....
Something else to think about:
- opening the throttle to activate the main system also pumps fuel in from the acc pump; how do you determine what is pump shot...& what is from the booster?
- if the O2 sensor says 'rich' about the same time the main system is expected to start, how do you determine whether it is JUST the main system fuel...or fuel coming from the tail end of the idle system?
- the reaction time of the O2 sensor to mixture variations.

 

[RustyRatRod]

@Newbomb Turk you’re writing AJ style posts except they're full of useful information.

Now that's funny right there, I don't care who you are. lol

 

[Newbomb Turk]

Somehow, I do not think all these people can be wrong....[ below ]. The last link is from the late John Passini, who wrote several books on carburation. He was English, hence some of the quaint phrases....
Something else to think about:
- opening the throttle to activate the main system also pumps fuel in from the acc pump; how do you determine what is pump shot...& what is from the booster?
- if the O2 sensor says 'rich' about the same time the main system is expected to start, how do you determine whether it is JUST the main system fuel...or fuel coming from the tail end of the idle system?
- the reaction time of the O2 sensor to mixture variations.

View attachment 1716411470

View attachment 1716411471

View attachment 1716411472

Read that VERY close.

They are talking about bleeding off signal. That only happens at high air flows when the booster has started.

C.F. Taylor covers this in his books. Larew and Obert do as well.

It seems these authors only discuss what the MAB does once the booster has started. Not what happens before it starts or getting it started.

Like I said above, at best they are half right. They really need to clean up how they write it because it causes massive confusion.

EDIT: read the last article very close. He is saying what I’m saying without actually saying it.

The emulsion stack gets its air from the MAB. Read it very close.

 

[92b]

Just to add to the confusion. I did a simple test on the dyno awhile back. My test was to see how main air bleed affected the timing of what rpm the booster started to flow. I tried various sized air bleeds and recorded the rpm at which the booster began to flow fuel. What I noticed was that regardless of main air bleed size the booster started flow at about the same rpm. In the last test I completely removed the main air bleed and the booster still started at the same rpm. I posted the results in a thread but I don't remember what thread it was. Maybe someone else does.

 

[TT5.9mag]

Just to add to the confusion. I did a simple test on the dyno awhile back. My test was to see how main air bleed affected the timing of what rpm the booster started to flow. I tried various sized air bleeds and recorded the rpm at which the booster began to flow fuel. What I noticed was that regardless of main air bleed size the booster started flow at about the same rpm. In the last test I completely removed the main air bleed and the booster still started at the same rpm. I posted the results in a thread but I don't remember what thread it was. Maybe someone else does.

What were the specifics of the carb? Do you know what emulsion stack was in it? And on what engine? Signal and amount of emulsion to the main well will affect how the MAB changes the booster.

 

[Newbomb Turk]

Just to add to the confusion. I did a simple test on the dyno awhile back. My test was to see how main air bleed affected the timing of what rpm the booster started to flow. I tried various sized air bleeds and recorded the rpm at which the booster began to flow fuel. What I noticed was that regardless of main air bleed size the booster started flow at about the same rpm. In the last test I completely removed the main air bleed and the booster still started at the same rpm. I posted the results in a thread but I don't remember what thread it was. Maybe someone else does.

I don’t remember that post but I’d love to read it if someone can find it.

Were you logging AFR while you were testing?

 

[92b]

Post in thread 'Annular boosters on a Tunnel Ram' Annular boosters on a Tunnel Ram

post108

 

[92b]

What were the specifics of the carb? Do you know what emulsion stack was in it? And on what engine? Signal and amount of emulsion to the main well will affect how the MAB changes the booster.

Check the thread I posted. Some of your answers are there.

 

[TT5.9mag]

Check the thread I posted. Some of your answers are there.

I do remember that now. I remember thinking when you posted that, I’d like to know the whole combination; compression, cu/in, carb size (750hp), and how much power it makes. I think at this point we all can agree that none of this stuff is set in stone or intuitive. Testing, testing, testing, is the ONLY way to know what will work on a specific combo. I’m looking for a quote from Tuner I posted here somewhere from RFS and it explained the relationship well and how all the variables interact. Be back shortly