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2898763_f520 AirFuel Carburettor_parts_carbs


THE FLOAT SYSTEM (Refer To Fig. 8)

The function of the float system is to maintain a constant level of fuel in the float chambers at all times and under all conditions of operation. Fuel enters the carburetor at the fuel inlet, flows through the float needle valve and seat and into the float chambers.

When the fuel reaches a given level, the floats shut-off the fuel supply at the needle valve. The float chambers are vented internally by a vent tube which connects the float chambers with the air horn


With the throttle valves closed, as shown in Figure 9, and the engine running at slow idle speed, fuel from the float chambers is metered into the idle tubes through an orifice at the base of each idle tube. The air taken in through the idle air bleed holes mixes with the fuel at the top of the idle tubes.

The mixture of air and fuel flows down the channels where it is mixed with additional air entering through the secondary idle air bleeds. The mixture is discharged at the lower idle discharge holes. The quantity of fuel discharged is controlled by adjustable idle needle valves. As the throttle valves are opened slightly, the air-fuel mixture is also discharged from the upper idle discharge holes to supply the additional fuel required for increased engine speed.


The main metering system controls the flow of fuel during the intermediate or part throttle range of operation. With the throttle valves in a partially open position, as shown in Figure 10, fuel flows from the float chambers through the main metering jets and enters the main discharge jets where it is mixed with air taken in through the high speed air bleeders.

This mixture of air and fuel is then discharged into the air stream through the auxiliary venturi tubes. The main body and main discharge jets are so designed that should vapor bubbles form in the fuel in the main discharge system, due to high temperatures, the vapor bubbles will collect in the outside channels surrounding the main discharge jets, rise and vaporize in the domes of the high speed bleeders, thus preventing “percolation.”


The power system is incorporated into the carburetor to provide a richer mixture for maximum power and high speed operation. The extra fuel for power is supplied by a vacuum controlled power piston which automatically operates the power by-pass jet in accordance with throttle opening.

Intake manifold vacuum is maintained above the vacuum piston through a vacuum channel which leads to the manifold flange of the carburetor, as shown in Figure 11. During partial throttle operation, the vacuum above the vacuum piston is sufficient to overrule the compression spring and hold the piston in the “UP” position.

When the throttle valves are opened to the point where the manifold vacuum drops to approximately four to five inches of mercury, the compression spring then moves the piston “DOWN” to open the power by-pass jet and meter additional fuel into the main metering system


To insure a smooth uninterrupted flow of power for acceleration, additional fuel must be metered into the engine. This is accomplished through the use of an accelerating pump which is operated by vacuum.

As the throttle valves are opened, the accelerating pump piston is moved “DOWN” either by a pump lever or by a drop in vacuum above the piston to close the inlet ball check valve and force a metered quantity of extra fuel through the outlet ball check valve and pump discharge nozzle into the air stream, as shown in Figure 12.

With the return of the accelerating pump lever to the released position or the return to normal engine vacuum, the outlet ball check valve “CLOSES” while the inlet ball check valve “REOPENS,” thus permitting fuel from the float chamber to enter and refill the accelerating pump cylinder, as shown in Figure 13.

Choke System

When the engine is cold, the fuel tends to condense into large drops in the manifold, rather than vaporizing. By supplying a richer mixture (8:1 to 9:1), there will be enough vapor to assure complete combustion. The carburetor is fitted with a choke system to provide this richer mixture. The choke system provides a very rich mixture to start the engine and to make the mixture less rich gradually, as the engine reaches operating temperature. The two types of choke systems are the manual and automatic:

  • The manual choke system (fig. 4-29) was once the most popular way of controlling the choke plate; however, because of emissions regulations the possible danger when used with catalytic converters and technological advances in automatic choke systems, manual chokes are not often used today. In the manual choke system, the choke plate is operated by a flexible cable that extends into the operator’s compartment. As the control is pulled out, the choke plate will be closed, so the engine can be started. As the control is pushed back in, the position of the choke plate is adjusted to provide the proper mixture. The following are two features that are incorporated into the manual choke to reduce the possibility of the engine flooding by automatically admitting air into the engine.




The mixing of the gasoline fuel with air so that a combustible mixture is obtained. The carburetor performs this job, supplying a combustible mixture of varying degrees of richness to suit engine operating conditions. The mixture must be rich ( have a higher percentage of fuel) for starting, accelleration, and high speed operation. A less rich ( leaner) mixture is desirable at intermediate speed with a warm engine. The carburetor has several system through which air-fuel mixture flows during different operating conditions. These systems produce the varying richness of the air-fuel mixture required for the varying operating conditions.


When a liquid changes to vapor ( gas form), it is said to evaporate. Water placed in an open pan will evaporate. It changes from a liquid to a vapor. Clothes hung on a line dry: the water in the clothes turn into vapor. When the clothes are well spread out, they dry more rapidly than they are bunched together. This illustrates an important fact about evaporation. The greater the surface exposed, the more rapidly evaporation takes place. A pint of water in a tall glass, takes a while to evaporate. But a pint of water in a shallow pan evaporates much more quickly.


In order to produce very quick vaporization of the liquid gasoline, it is sprayed into the air passing through the carburetor. Spraying the liquid turns it into many fine droplets. This effect is called atomization because the liquid is broken up into small droplets (but not actually into atoms, as the name implies). Each droplet is exposed to air on all sides so that it vaporizes very quickly. Thus, during normal running of the engine, the gasoline sprayed int the air passing through the carburetor turns to vapor, or vaporizes almost instantly.


A simple carburetor could be made from a round cylinder with a constricted section, a fuel nozzle, and a round disc, or valve. The round cylinder is called air horn . The constricted section the venturi, and the valve the throttle valve. The throttle valve can be tilted more or less to open or close the air horn. In the horizontal position , it shut off, or throttles, the air flow through the air horn. When the throttle is turned away from this position, air can flow through the air horn.


As air flows through the constriction, or venturi, a partial vacuum is produced at the venturi. This vacuum causes the fuel nozzle to deliver a spray of gasoline into the passing air 

stream. The venturi effect ( of producing a vacuum) can be illustrated with the set up of a drawing showing three dishes of mercury ( a heavy metallic liquid ) are conned by a tubes to an air horn with a venturi. The greater the vacuum, the higher the mercury is pushed up in the tube by atmospheric pressure. Note that the greatest vacuum is right at the venturi. Also, it should be remembered that the faster the air flows through, the greater the vacuum.

Why is there a vacuum in the venturi? A simple explanation might be as follows: The air is made up of countless molecules. As air moves into the top of air horn, all the air molecules move at the same speed. But if all are to get through the venturi, they must speed up and move through faster. For instance, let us look in two molecules, one behind the other. As the first molecule enters the venturi, it speeds up, tending to leave the second molecule behind. The second molecule also speeds up as it enter the venturi. But the first molecule has , in effect, a head start. Thus, the two molecules are further apart in the venturi than they were before they entered it. Now, imagine a great number of particles going through the same action. As they pass through the venturi, they are further apart than before they entered. This is just another way of saying that a partial vacuum exist in the venturi. A partial vacuum is thinning out of the air, more-than-normal distance between air molecules.


The partial vacuum occurs in the venturi, just where the end of the fuel nozzle is located. The other end of the fuel nozzle in a fuel reservoir (the float bowl). Atmospheric pressure pushes o the fuel through a vent in the float-bowl cover. With the vacuum at the upper end of the nozzle, fuel is pushed up through the nozzle. The fuel enters the passing air stream as a fine spray. It quickly turns to vapor as the droplets of fuel evaporate. The more air that flows through the air horn, the greater the vacuum in the venturi. The greater the vacuum, the more fuel is delivered.


The throttle valve can be tilted in the air horn to allow more or less air to flow through. When it is tilted to allow more air to flow, larger amount of air-fuel mixture is delivered to the engine. The engine develops more power and tends to run faster. But if the throttle valve is positioned (tilted) to throttle off, then only small amount of air-fuel mixture is delivered . The engine produces less power and tends to slow down. The throttle valve is linked to an accelerator pedal in the driver’s compartment. This permits the driver to position the throttle valve to suit operating requirements.


The fuel system must vary the air-fuel ratio to to suit different operating requirements. The mixture must be rich ( have a high proportion of fuel) for starting. It must be leaner ( have a lower proportion of fuel) for part-throttle medium-speed operation. ( See graph of of air-fuel ratios as related to various car speed.) Ratios, and the speed at which they are obtained , vary with different cars. In example shown, a rich mixture of about 9:1 ( 9 pounds of air to each pound of fuel ) is supplied for starting. Then during the idle, the mixture leans out to about 12:1 atr medium speed, the mixture further leans out to about 15:1. But at higher speeds, with a wide opened throttle, the mixture is enriched to about 13:1 . Opening the throttle for acceleration at any speed causes a momentary enrichment of the mixture. This result from special carburetor system which we will study later.


The systems (or circuits as they are sometimes called) in the carburetor are:

1. Float system

2. Idle system

3. Main-metering system

4. Power system

5. Accelerator-pump system

6. Choke system FLOAT SYSTEM

The float system includes the float bowl and a float and needle-valve arrangement. The float and the needle valve maintain a constant level of fuel in the float bowl. If the level is too high, then too much fuel will feed from the fuel nozzle. If it is too low, too little fuel will feed. In either event, poor engine performance will result. (see simplified drawing of a carburetor float system) If fuel enters the float bowl faster than it is withdrawn, the fuel level rises. This causes the float to move up and push the needle valve into the valve seat. This, in turn, shut off the fuel inlet so that no fuel can enter. Then, if the fuel level ddrops, the float moves down and releases the needle valve so that the fuel inlet is opened. Now fuel can enter. In actual operation, the fuel is kept in an almost constant level. The float tends to hold the needle valve partly closed so that the incoming fuel just balances the fuel being withdrawn.

A number of years ago, some 4 barrel carburetors had two sets of float. The four barrel carburetor is, in effect, two barrel carburetors. The primary barrels supply the engine during most operating conditions. But the secondary barrels come in operation during acceleration and high speed, for improved performance. The idea of using two floats was to provide, in effect, separate float systems for each pair of barrels. However, more recent four barrel carburetors have a single centrally located float. The two-float system requires a large float bowl and has other disadvantages that the single or dual floats do not. For example, the single or dual floats are more centrally located so they respond more accurately to fuel needs. Also the float bowl is smaller so less of a problem of evaporation and less possibility of atmospheric pollution from escaping HC.


The float bowls of carburetors are vented into the carburetor air horn at a point above the choke valve. The purpose of the vent is to equalize the effects of a clogged air cleaner. For example, suppose the air cleaner has become clogged with dirt. The passage of air through it is then restricted. As a result, a partial vacuum develops in the carburetor air horn. Therefore somewhat greater vacuum is applied to the fuel nozzle (since this vacuum is added to the venturi vacuum.) However, the partial vacuum resulting from the clogged air cleaner is also applied to the float bowl (through the vent). Therefore, the only driving force that pushes pressure. Thus, the vent makes up for the effect of a clogged air cleaner. If the bowl were vented to the atmosphere, then atmospheric pressure would be the driving force. This would produce a greater fuel flow from the fuel nozzle, and the mixture would be too rich.


When the throttle is closed or only slightly opened, only a small amount of air can pass through the air horn. The air speed is low, and very little vacuum develops in the venturi. This means that the fuel nozzle does not feed fuel. Thus, the carburetor must have another system to supply fuel when the throttle is closed or slightly opened.

This system, is called the idle, it includes passages through which air and fuel can flow. The air passage is called the air bleed. With the throttle closed, there is a high vacuum below the throttle valve from the intake manifold. Atmospheric pressure pushes air and fuel through the passages . They mix and flow pastthe tapered point of the idle air-fuel- mixture adjustment screw. The mixture has a high proportion of fuel (very rich). It leans out somewhat as it mixes with the small amount of air that gets past the closed throttle valve. But the final mixture is still rich enough for good idling. The richness can be adjusted by turning the idle

Air-fuel-mixture adjustment screw in or out. This permit less or more air-fuel mixture to flow past the screw.

CAUTION: In late model cars, the idle air-fuel mixture screw is fixed or has a locking cap on it. The reason for this is that it is illegal to adjust the idle mixture beyond specific limits. It has been set according to federal standards and must not be tampered with.


Suppose the throttle valve is opened enough so that its edge moves well past the low speed port. Now there is little difference in vacuum between the upper and lower parts of the air horn. Thus little air-fuel mixture discharges from the low-speed port. However, under this condition,, enough air moves through the air hoprn to produce a vacuum in the venturi. As a result, the fuel nozzle centered in the venturi ( called the main nozzle or high speed nozzle) begins to discharge fuel. The main nozzle supplies the fuel during operation with the throttle 

pqrtly to fully opened. The circuit from the float bowl to the main nozzle is called the main metering system.

The wider the throttle is opened and the faster the air flows through the air horn, the greater the vacuum in the venturi. This means that additional fuel will be discharged from the main nozzle (because of the greater vacuum). As a result, a nearly constant air-fuel ratio is maintained by the main metering system from part –to-wide –open throttle.


For high speed full power wide open operation, the air-fuel mixture must be enriched. Additional devices are incorporated in the carburetor to provide this enriched mixture during high speed full power operation. They are operated mechanically or by intake manifold vacuum.


This system includes a metering rod jet ( a carefully calibrated orifice or opening ) and metering rod with two or more steps of different diameters. The metering rod is attached to the throttle linkage. When the throttle is opened, the meteering rod is lifted. But wheb the throttle is partly closed, the larger diameter of the metering rod is in the metering–rod jet. This partly restricts fuel flow to the main nozzle. However, enough fuel does flow for normal part-throttle operation. When the throttle is open wide, the rod is lifted enough to cause the smaller diameter , or step, to move up into the metering rod jet. Now, the jet is less restricted, and more fuel can flow. The main nozzle is therefore supplied with more fuel, and the resulting air-fuel mixture is richer.


This system is operated by intake manifold vacuum. It includes a vacuum piston or diaphragm linked to a valve or a metering rod. In one of the many designs, during the part throttle operation, the piston is held in the lower by intake manifold vacuum. However, when the throttle is opened wide, manifold vacuum is reduced. This allows the spring under the vacuum piston to push the piston upward. This motion raises the metering rod so that the smaller diameter of the rod clears the jet. Now more fuel can flow to handle the full power requirements of the engine.

A carburetor use a spring- loaded diaphragm to control the position of the metering rod. The action is similar to that of the carburetor using a spring loaded piston. When the throttle is opened so that intake manifold vacuum is reduced, the spring raises the diaphragm. This allows the metering rod to be lifted so that its smaller diameter clears the jet, allowing more fuel to flow.


In some carburetors, a combination full power system is used. It is operated both mechanically and by vacuum from the intake manifold. In such carburetor, a metering rod is

linked to a vacuum diaphragm as well as to the throttle linkage. Thus, movement of the throttle to “full open” lifts the metering rod to enrich the mixture. Or loss of intake manifold vacuum (as during a hard pull up a hill or during acceleration) causes the vacuum diaphragm spring to raise the metering rod for an enriched mixture.


Mahalagang Pangarap

     Kung ikaw ang tatanungin ano ang iyong pangarap?

     Siyempre kung ako ang tatanungin mangangarap ako na buo ang aking pamilya dahil
mahalaga sa akin ito. At mahal na mahal ko sila dahil mahahalaga at sila ang nag-alaga at nagtiyagang palakihin ako. At kung mawawala sila parang maglalaho ang buhay ko at mawawalang saysay ito.

     Meron akong kilala na may katulad sa sitwasyon ko nangangarap siya na sana matagal pa niya makasama ang kanyang pamilya dahil nga may sakit ang mga ito. Ito ay si Rayl at magkatulad kami ng pangarap gusto namin makasama ang aming pamilya ng matagal upang sila naman ang aalagaan namin. At gusto niya rin sama-sama lahat sila upang masaya ang pamilya. Dahil mahal niya ang mga ito.

     At kung mangangarap talaga ako gusto ko makasama ko pa ng matagal ang aking pamilya dahil mahal na mahal ko sila.

Raor at Lemnir

Cedrick -> Ang lalaking matapang
Lemnir ->Ang asawa ni Cedrick
Raor ->Ang pinaghihinalaan ni Lemnir

  Sa bahay at mall .

Lemnir :Bakit wala nanaman si Cedrick.
             Saan nanaman siya.
              (Nakalipas ang isang oras)
Lemnir :Oh! Cedrick saan ka pumunta?
Cedrick :Wala naman. Pumunta lang ako sa mall.
Lemnir :ano naman ginawa mo? Sino kasama mo?
Cedrick :Wala ako kasama! (Habang kabado)
             (Ilang saglit umalis ulit si Cedrick at nagtaka
              si Lemnir. Sinundan niya ito.)
Lemnir : Ah…h.h.h. kaya pala lagi ka wala kasi
            may kasama kang iba.
Cedrick :Sino kang babae ka?
Raor :Anong sino? Diba magkasama tayo.
         Hoy! babae.. ako kirida ng asawa mo.
Lemnir :Ah! Ikaw ba yun! Isa kang taksil
            Cedrick. Minahal kita tapos ganyan .
Cedrick :Hindi na kita mahal! Ayaw ko na sayo.
Lemnir :mas hindi kita mahal! Taksil!!!
            Maghiwalay na tayo.

            *Wakas* …..

Pangalagaan. Inang kalikasan

Maduming paligid, ang linisin natin.
Upang tayo’y maging, mas linisin natin,
HUwag magtatapon, kahit saan-saan,
Upang ang epekto, ay magbago naman.

Inang kalikasan, ating alagaan.
At sa ating buhay, ito’y ating yaman.
Huwag makinig at, may isip at puso.
Sa mundong ito ay, isinilang ako.

Kailangan natin, magsama-sama at,
Magtulungan upang, bumuo ng isang,
Organisadong grupo, upang makatulong,
Sa isang layuning, pangkapaligiran.