The edelbrock carburetor has three 3 basic systems that meter fuel to the engine. An altitude compensating system of a carburetor for obtaining a desirable enriched air fuel ratio. Carburetor according to the type of metering system. Learn vocabulary, terms, and more with flashcards, games, and other study tools. To carburate or carburet and thus carburation or carburetion, respectively means to mix the air and fuel or to.
The main metering system supplies fuel to the engine at all speeds above idling. Introduction the stromberg nars, narsa, and nar6 carburetors are designed to meet the. A carburetor american english or carburettor british english is a device that mixes air and fuel for internal combustion engines in the proper airfuel ratio for combustion. The main advantage of this system is that it is not affected. An orifice bypassing the check valve allows fuel to be drawn up from the fuel tank, through the carburetor fuel pump, metering system and into the primer bulb. The following text will describe the opera tion of these systems for ease in troubleshooting. Metering characteristics of carburetors unt digital library. The autolite model 4300 carburetor operation, adjustment and overhaul vol. By understanding the operation of each you will be better prepared to calibrate your carburetor. The free end of the metering lever should be 0 to 0. The idle system supplies the airfuel mixture to operate the engine at idle and low speeds. These particular power valves are located in the metering block of the carburetor behind the jets so changes are relatively simple and straightforward. This, therefore, gives a basic carburetor with a wide range of r. Quadrajet carburetor 4mv4mcm4mem4mc service manual 9d5.
By addition of a stepped tapered fuel metering needle, the fuel can now be metered in relationship to the choke venturi size and throttle plate poition. The diaphragm defines in part a pressure controlled fuel metering chamber on one side and a reference chamber at atmospheric pressure on the other side. The idle system, primary main system, and secondary main system. The 0807871 and 0805831 are designed as universaltype, 2barrel racing carburetors. Walbro wyj carburetor manual and parts list for the correct identification, repair and service of the wyj series carburetor found in trimmers and blowers. This is the metering area of this rodjet combination with the rod fully inserted in the jet. The amount of fuel added is dependent upon the size of the power valve channel restriction in the metering block. The fundamental parts of the carburetor idle system include a section of the main discharge tube, a low speed jet, an idle air bleed, a bypass, a idle passage, an economizer, an idle screw port, and an idle mixture screw. Unbolt and remove the carburetor from the manifold. View free online images or download the full walbro wyj carburetor manual pdf which can be printed or saved on any suitable device using a pdf reader. View and download yamaha xj700n service manual online. The small amount of air is supplied through the air jet position on the outer face of. Choke system there are six different systems fuelair circuits in a carburetor that make it work. The recommended disassembly, cleaning, inspection and assembly procedures are also given.
Fuel from the fuel bowl passes through the mixture metering sleeve, fuel channel, power jet, and into the main nozzle bore, where it passes through the idle supply opening in main nozzle, through the. At idle speeds and up to approximately 1,000 to 1,300 rpm the main jet has little or no fuel passing through it. This carburetor body serves as the mounting point for the various essential carburetor system components, which are grouped together to create carburetor circuits. The main disadvantage of basing a carburetor s operation on bernoullis principle is that, being a fluid dynamic device, the pressure reduction in a venturi tends to be proportional to the square of the intake airspeed. A fuel metering system for a combustion engine carburetor utilizes a nonconvoluted, planar, flexible diaphragm which does not require a molding process to form a traditional convolution. The fuel jets are much smaller and fuel flow is limited mainly by the fuels viscosity, so that the fuel flow tends to be. It is sometimes colloquially shortened to carb in the uk and north america or carby in australia. Each of the carburetor circuits is designed to provide a certain function to the carburetor. May 12, 2019 this is an electronic reproduction of the original ford printed manual. This is because the throttle valve is almost closed and there is little air swept past the discharge nozzle. When the air passes through venturi, it generates a lowpressure field across the throat.
Fuel metering system powerplant flashcards quizlet. The main metering system is designed to supply the leanest fuel mixture for cruising in the 35 mph and over range. A separate system is necessary for idling because the main metering system can be erratic at very low engine speeds. Fuel metering is controlled by the main metering jets and the power valve, that adds additional fuel as needed, and which is restricted or opened by a combination of vacuum and spring pressure. The float system figures 6 or 7 consists of a fuel. However, the main metering system is required to supply fuel to the engine both at. The main metering jet is placed in the fuel passage between the float chamber and the discharge nozzle.
Main jet main metering system as the throttle plates open in response to speed andor load demand, the air flow through the carburetor main venturi increases in velocity, inducing an increased depression on the main metering system, causing airfuel mixture to flow from the main discharge nozzle. View product sample this is an electronic reproduction of the original ford printed manual. Us4153652a altitude compensating system of a carburetor. Metering systems the edelbrock carburetor has three 3 basic systems that meter fuel to the engine. Wyj starting procedure by depressing the purge bulb 45 times, air is forced through the umbrella check valve. Quadrajet carburetor 4mv4mcm4mem4mc service manual.
Nov 10, 2017 a basic carburettor has two jets, an idling jet and a main jet. Technical information bulletin the corvette restoration page. With metering diaphragm cover 4 screws, metering diaphragm and gasket removed. Models 2g, 2gc, 2gv service manual carburetor parts. What system must supply fuel to the carburetor or the metering device under all conditions of ground and air operation. It also gives a description of the bureau of standards carburetor test plant, test equipment and measuring instruments used to determine. Report presents the results of an extensive experimental investigation of the performance of different types of carburetors as effecting the maintenance under all conditions of correct ratio between the weights of fuel and air. What is the main metering system in a simple carburetor. There are six different systems airfuel circuits in a carburetor that make it work. Its purpose is to limit the fuel flow when the throttle valve is wide open. Floattype carburetors main metering system flight mechanic.
Autolite model 4300 carburetor pdf download ford manuals. Engine vacuum pulls this airfuel mixture and discharges it through the. Main metering system the main metering system is designed to supply the leanest fuel mixture for cruising in the 35 mph and over range. Fuel from the engine fuel pump first passes through the fuel inlet filter and on through the float needle seat, past the float needle into the carburetor float bowl. At low rpms, the idling system is independent of the main metering jet. This is an electronic reproduction of the original ford printed manual.
The purpose of the metering system is to control fuel flow. B if the metering lever is the same as figure b in the following schematic, the free end of the metering. The metering system used in the carburetor is of the plain tube type with an air bleed to the main discharge nozzle which is secured in a boss in the air intake with the discharge holes near the center of the venture. Install the carburetormounting studs provided in the proper location on the intake manifold carburetor. The lowspeed jet is a restriction in the idle passage that limits maximum fuel flow in the idle system. What is the fuel metering force in a floattype carburetor. Its operation is much like a float and inlet needle on a conventional float bowl carburetor. Edelbrock performer 1406 owners manual 39 pages performer series carburetor. Carburetor models carburetor qwtels listed on side of indicate the side used for that carburetor metering system. Float system the quadrajet carburetor has a centrally located fuel chamber in the float bowl figure 5.
The fuel discharged by this system is determined by the drop in pressure in the venturi throat. The main advantage of this system is that it is not affected by the orientation of the engine. The fuel chamber is centered between the carburetor bores to assure an adequate fuel supply to all metering systems with respect to car inclination or severity of turns. There are six basic systems used in the rochester model g 2bore carburetor.
In other words, this is the metering area at cruise speed and at idle. A if the metering lever is the same as figure a in the following schematic, place a straight edge or zama z gauge across the carburetor body. Carburetor basics tech article chevy high performance magazine. Fuel from the main metering jet enters the main well and is mixed with air from the high speed air bleed. The way these systems are arranged in the carburetor determines the carburetor s size and shape. In order to operate in any position, the systems normally on gravity namely the float and inlet needle, and the gravity flow fuel system need to be replaced with mechani cal devices. A basic carburettor has two jets, an idling jet and a main jet. Us20020195726a1 fuel metering system for a carburetor. The main metering system supplies fuel to the engine at all speeds above idling and consists of. In the air bleed jet types of carburetors, the fuel is supplied to the main discharge nozzle through the main metering jet at low speeds.
As the main metering system will not function at very low air flows low engine speed an idling system is provided. The basics of jetting a holley carburetor racingjunk news. The secondary unit has its one float bowl and a dual carburetor main metering system and idle system. Jul 14, 2017 the fuel enrichment circuit of a holley carburetor is based upon a power valve system. In holleys quest for maximum performance and tuneability, this carburetor 0807871 has been updated with a new metering block with changeable emulsion bleeds.
Dec 14, 2016 carburetor main fuel system with the throttle plate fully open, the carburetor main fuel system takes effect. The diaphragm carburetor replaces the float with a metering diaphragm and uses a fuel. A typical main metering system is illustrated in figure 212. This consists of an idle tube with an idle metering orifice near the bottom and air bleed holes in the side, an idle air bleed and an adjustable idle discharge nozzle.
It is responsible to form a correct mixture of airfuel. With the throttle fully closed, the idle jet provides just enough fuel to allow the engine to idle, usually somewhere between 400 and 800rpm. This system will add approximately 68 jet numbers of fuel to the engine under demand. Permanent jets and air bleeds calibrate the main metering system for efficient part throttle operation.
They are float, idle, main metering, power, accelerator pump and choke systems. Carburetor main fuel system with the throttle plate fully open, the carburetor main fuel system takes effect. Main jet main metering system as the throttle plates open in response to speed andor load demand, the air flow through the carburetor main venturi increases. Since the throttle valve controls the mass airflow through the carburetor venturi, it must be considered a major unit in the main metering system as well as in other carburetor systems. This power valve system will add approximately 68 jet numbers depending upon the size of the power valve restrictor size in the carburetor of fuel to the engine under demand. Fuel level is very important, because it must be maintained to give proper carburetor metering throughout all ranges of engine operation. This allows you to tune your fuel curve to match your engines performance.
Venturi main metering jet main discharge nozzle passage. Metering lever adjustment instructions are pictured below using our metering lever gage. The fuel pump on a diaphragm carburetor uses the vacuum and pressure pulse from the engines. Start studying engine fuel and fuel metering systems. Adjusting the metering lever c, lever gage soc 500 1. A carburetor doesnt really need a powerenrichment circuit.
The metering system controls the flow of fuel into the nozzle. If the intake manifold is being changed at this time, install the new manifold according to the manifold manufacturers directions. The way these systems are arranged in the carburetor determines the carburetors size and shape. The six circuits are the float, idle, main metering, power, accelerator pump, and choke. This air passes through the pump body and out the overflow tube. Technical information bulletin the corvette restoration. Whats the purpose of a main metering system in a carburetor. Some wyj carburetors have as an option a purge system, this purge system allows the customer to purge the metering system of air and replace it with fuel for easier starting.