Holy Grail Carb

[dwilfong]

David thy where used with ex throttles ?

 

[Jim Allen]

.625" & .725" bore, automatic fuel metering, type carburetors have been used on both gas & nitro engines for many years.

JA

 

[Tom Foley]

David thy where used with ex throttles ?

Barrel rotates within the housing along with the "Ring of fuel " without obstructions .

 

[dwilfong]

The one I have is like a normal carb.

The ring is in the rotating barrel.

 

[Tom Foley]

The one I have is like a normal carb.

The ring is in the rotating barrel.

I think that's what I said lol .

Barrel rotates within the housing along with the "Ring of fuel " without obstructions .

 

[David Bryant]

David thy where used with ex throttles ?

yep, sorry, meant to add: those two Cee Bee carb's (above) are straight "Jet Ring" venturi's, not rotating barrel carburetors. And they are meant to be used with an exhaust throttle. But they give you some idea on what the "annular" style discharge ring looks like.

 

[Charles Perdue]

Almost any design carb, consisting of two or more tubes will work to some degree. Even the very basic one consisting of one large tube for the carb bore with another tube coming in from the side carrying the fuel will work. The differences beyond that is how well it meters the fuel to what the engine requires and to what degree that it vaporizes the fuel and keeps the fuel suspended in the airflow among other requirements. The fact that in our nitro engines, we require about a 4 to 1 air/fuel ratio, makes it very difficult to vaporize and keep the fuel suspended in the airflow

Before I began to build my own carbs, I collected and borrowed many carbs including some of Mr. Carl Breys carbs. I also made more than one or two different carbs designs including different styles of the annular discharge carbs. (I even made a toy boat carb with a flexible bore for a variable-venturi carb, was too difficult to manufacture)

While the annular discharge carbs were better than a lot of the other designs available at that time, the largest drawback to them was, after they vaporized the fuel, they were not able to keep the fuel from collecting back on the insides of the carb bore. The reason for this is the highest velocity of the air through the carb is down the center of the bore. The closer to the inside wall of the carb bore, the slower the velocity is. This is where the annular discharge carbs dispense their fuels. This along with the shape of the venturi, would cause a vortex (tumbling) in the air/fuel mixture and this would push the fuel back toward the inside of the carb bore where it would condense back into larger droplets of fuel.

There will be some that disagree, but look it up for yourself, the different designs of the discharge nozzles used on automotive racing carbs and you will find the different types used and their benefits and drawbacks. Where the annular discharge designs are used, they are kept very short to help offset this problem. That and the gasoline/alcohol fuels are much easier to keep in suspension.

Charles

 

[dwilfong]

Charles

I had a great conversation with Andy at the nitro nats this year about fuel delivery. Jerry and Danny where there and could not believe he was giving up the farm.........LOL

The closer the fuel delivery to the window be it drum or disk has a big influlance on how the fuel stays in suspension.

Not every eng intake design will utilize the same fuel delivery system.

The closer to the window and how it flows in to the case have a lot to do with what works best.

I will hold my tong about any more ........

lets just say it takes two needles to do it right................................

Then again it may not be in the carb at all..........................................

 

[Danny King]

Charles

I had a great conversation with Andy at the nitro nats this year about fuel delivery. Jerry and Danny where there and could not believe he was giving up the farm.........LOL..

Not the first time I've seen him do this. LolAbout 25 yes ago I went to Indy with Andy. We ended up at either Marty Davis or John ackermans house but both of them were there. . And Andy started talking and I couldn't believe how much stuff he was revealing. Lmao. Keep in mind this was long before the Internet was utilized. Areas of the country did things different from others. Most guys would only talk to each other a cpl times a year.

Andy is not a bs'r so if he's talking it's worth trying to understand.

There are so many ideas to try in this hobby. We are nowhere near maximizing the hp especially in bigger motors.

 

[Danny King]

Danny

A 17mm / .670 butter fly will flow more than enough. The venture will be .600

The booster venture is designed to draw the fuel with the step it has made into it.

Yes the MAC .550 is my favorite stock carb.

You ever run that monster I sold you???????????????

No I haven't. In the last cpl weeks I just played with the 101 sg. First time since the nitro winter race. It's running 91 in full heat trim. Poor old boat is having a hard time staying together. So I need to redo it. I can't run it right now. I was just about to put that carb and plate on. I am running a dbl plug head but not the one u made. Atleast not yet. So much to try. So little time.

 

[dwilfong]

Yes there is a lot that has not bin tested to it full potential that is for sure.

Went out and bought a very small servo controlled pump that will hook to the receiver to try.

Direct injection will be the next thing I will try to achieve when I get back to testing.

I pulled mine out for the first time since Jan and found the tub was cracked again.

New boat is the next step for me also.

 

[David Bryant]

New boat is the next step for me also.

a new SGX?

 

[BobBonahoom]

I have a question for you guys about this. As the methanol vaporizes it cools a lot, which must hurt the vaporization of the nitro. I looked up the vapor pressure of nitromethane and it pretty low to begin with. It boils at 212 degrees F (same as water). At 80 degrees F only 5% of the liquid would be a vapor, but at 180 degrees F, 53% would be a vapor. Has anyone ever tried heating the fuel just before it enters the carb?

 

[Charles Perdue]

Bob when you heat the fuel or fuel/air mixture, it expands so it is less dense and you are actually allowing less fuel to enter the cylinder. One way around this is to compress this mixture in the engine.

Smokey Yunick, of NASCAR fame, designed a fuel setup like this using a turbo charger to keep this mixture the same density as it would be at normal temperatures. It worked great but the auto manufactures were not interested.

You can look this up as it was tested by Popular Mechanics Magazine.

Charles

 

[John Beardslee]

I have a question for you guys about this. As the methanol vaporizes it cools a lot, which must hurt the vaporization of the nitro. I looked up the vapor pressure of nitromethane and it pretty low to begin with. It boils at 212 degrees F (same as water). At 80 degrees F only 5% of the liquid would be a vapor, but at 180 degrees F, 53% would be a vapor. Has anyone ever tried heating the fuel just before it enters the carb?

Hi Bob,

A while back I asked Marty if he had checked the temperature of the gasses at the pipe pressure tap to fuel tank to see what might be going into the tank. My reason was to consider what type of filter I could use in the line - not really as cerebral as this conversation. At any rate he said he'd measured 720F so I would think that there is some heating of the fuel in the thank going on already but not sure how much. Something to at least consider.

Thanks, John

 

[dwilfong]

I brought up Smoky and heating the fuel a few years ago on one thread.

Now if you supper heat just the nitro and servo pump inject it in the cylinder????????

Open venture at the intake flowing just meth and oil mix. Ex throttle for control.

One of my brain storms that wont be settled till I try it...........LOL

 

[Tom Foley]

Some good thoughts here , I knew this would be informative . David , you are crazy !!!

 

[dwilfong]

It has bin tested already that all I will say...........................................

 

[shoboat]

David,

I think you need a carbon tub for your next test boat?

Those bigger motors just stress a wood tub out beyond belief.

The direct injection idea sounds promising, but computer

controlled fuel injection cannot be that far away? I know

some of the aero guys are working in this direction already.

Keep Thinking Of New Ideas,

Mark Sholund

 

[Jeff Lutz]

Yes there is a lot that has not bin tested to it full potential that is for sure.

Went out and bought a very small servo controlled pump that will hook to the receiver to try.

Direct injection will be the next thing I will try to achieve when I get back to testing.

I pulled mine out for the first time since Jan and found the tub was cracked again.

New boat is the next step for me also.

. I've put some fuel nipples in strange places myself..... And drilled holes in strange places also.... True direct injection like a Mercury optimax is fuel shot in with the exhaust completely sealed, (very difficult on our model engines) but there are some different ways to feed fuel to our engines and not fight the drum valve.