103-813: A carburetor (also spelled carburettor or carburetter ) is a device used by a gasoline internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the Venturi tube in the main metering circuit, though various other components are also used to provide extra fuel or air in specific circumstances. Since the 1990s, carburetors have been largely replaced by fuel injection for cars and trucks, but carburetors are still used by some small engines (e.g. lawnmowers, generators, and concrete mixers) and motorcycles. In addition, they are still widely used on piston engine driven aircraft. Diesel engines have always used fuel injection instead of carburetors, as
206-433: A carburetor or fuel injection as port injection or direct injection . Most SI engines have a single spark plug per cylinder but some have 2 . A head gasket prevents the gas from leaking between the cylinder head and the engine block. The opening and closing of the valves is controlled by one or several camshafts and springs—or in some engines—a desmodromic mechanism that uses no springs. The camshaft may press directly
309-419: A cold start . In order to ensure an adequate supply at all times, carburetors include a reservoir of fuel, called a "float chamber" or "float bowl". Fuel is delivered to the float chamber by a fuel pump . A floating inlet valve regulates the fuel entering the float chamber, assuring a constant level. Unlike in a fuel injected engine, the fuel system in a carbureted engine is not pressurized. For engines where
412-409: A deflector head . Pistons are open at the bottom and hollow except for an integral reinforcement structure (the piston web). When an engine is working, the gas pressure in the combustion chamber exerts a force on the piston crown which is transferred through its web to a gudgeon pin . Each piston has rings fitted around its circumference that mostly prevent the gases from leaking into the crankcase or
515-428: A gas engine . Also in 1794, Robert Street patented an internal combustion engine, which was also the first to use liquid fuel , and built an engine around that time. In 1798, John Stevens built the first American internal combustion engine. In 1807, French engineers Nicéphore Niépce (who went on to invent photography ) and Claude Niépce ran a prototype internal combustion engine, using controlled dust explosions,
618-470: A locomotive operated by electricity.) In boating, an internal combustion engine that is installed in the hull is referred to as an engine, but the engines that sit on the transom are referred to as motors. Reciprocating piston engines are by far the most common power source for land and water vehicles , including automobiles , motorcycles , ships and to a lesser extent, locomotives (some are electrical but most use diesel engines ). Rotary engines of
721-410: A rotor (Wankel engine) , or a nozzle ( jet engine ). This force moves the component over a distance. This process transforms chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to. The first commercially successful internal combustion engine was created by Étienne Lenoir around 1860, and the first modern internal combustion engine, known as
824-466: A venturi (aka "barrel"). Fuel is introduced into the air stream through small tubes (the main jets ) at the narrowest part of the venturi, where the air is at its highest speed. Downstream of the venturi is a throttle (usually in the form of a butterfly valve ) which is used to control the amount of air entering the carburetor. In a car, this throttle is connected to the vehicle's throttle pedal, which varies engine speed. At lesser throttle openings,
927-594: A battery and charging system; nevertheless, this system is secondary and is added by manufacturers as a luxury for the ease of starting, turning fuel on and off (which can also be done via a switch or mechanical apparatus), and for running auxiliary electrical components and accessories. Most new engines rely on electrical and electronic engine control units (ECU) that also adjust the combustion process to increase efficiency and reduce emissions. Surfaces in contact and relative motion to other surfaces require lubrication to reduce wear, noise and increase efficiency by reducing
1030-404: A carefully timed high-voltage to the proper cylinder. This spark, via the spark plug, ignites the air-fuel mixture in the engine's cylinders. While gasoline internal combustion engines are much easier to start in cold weather than diesel engines, they can still have cold weather starting problems under extreme conditions. For years, the solution was to park the car in heated areas. In some parts of
1133-499: A common power source for lawnmowers , string trimmers , chain saws , leafblowers , pressure washers , snowmobiles , jet skis , outboard motors , mopeds , and motorcycles . There are several possible ways to classify internal combustion engines. By number of strokes: By type of ignition: By mechanical/thermodynamic cycle (these cycles are infrequently used but are commonly found in hybrid vehicles , along with other vehicles manufactured for fuel efficiency ): The base of
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#17327810031071236-429: A flexible diaphragm on one side of the fuel chamber, connected to a needle valve which regulates the fuel entering the chamber. As the flowrate of the air in the chamber (controlled by the throttling valve/butterfly valve) decreases, the diaphragm moves inward (downward), which closes the needle valve to admit less fuel. As the flowrate of the air in the chamber increases, the diaphragm moves outward (upward) which opens
1339-452: A hand crank. Larger engines typically power their starting motors and ignition systems using the electrical energy stored in a lead–acid battery . The battery's charged state is maintained by an automotive alternator or (previously) a generator which uses engine power to create electrical energy storage. The battery supplies electrical power for starting when the engine has a starting motor system, and supplies electrical power when
1442-408: A heat stove around the exhaust manifold. It was connected to the air filter intake via tubing and supplied warmed air to the air filter. A vacuum controlled butterfly valve pre heat tube on the intake horn of the air cleaner would open allowing cooler air when engine load increased. Internal combustion engine An internal combustion engine ( ICE or IC engine ) is a heat engine in which
1545-440: A low-pressure area in the idle passage/port thus causing fuel to flow through the idle jet. The idle jet is set at some constant value by the carburetor manufacturer, thus flowing a specified amount of fuel. Many carburetors use an off-idle circuit, which includes an additional fuel jet which is briefly used as the throttle starts to open. This jet is located in a low-pressure area behind the throttle. The additional fuel it provides
1648-457: A patent for a "gas or vapor engine", which ran on turpentine mixed with air. The design did not reach production. In 1875 German engineer Siegfried Marcus produced a car powered by the first petrol engine (which also debuted the first magneto ignition system). Karl Benz introduced his single-cylinder four-stroke powered Benz Patent-Motorwagen in 1885. All three of these engines used surface carburetors, which operated by moving air across
1751-408: A problem would occur as the compression ratio increased as the fuel was igniting due to the rise in temperature that resulted. Charles Kettering developed a lead additive which allowed higher compression ratios, which was progressively abandoned for automotive use from the 1970s onward, partly due to lead poisoning concerns. The fuel mixture is ignited at different progressions of the piston in
1854-731: A reciprocating internal combustion engine is the engine block , which is typically made of cast iron (due to its good wear resistance and low cost) or aluminum . In the latter case, the cylinder liners are made of cast iron or steel, or a coating such as nikasil or alusil . The engine block contains the cylinders . In engines with more than one cylinder they are usually arranged either in 1 row ( straight engine ) or 2 rows ( boxer engine or V engine ); 3 or 4 rows are occasionally used ( W engine ) in contemporary engines, and other engine configurations are possible and have been used. Single-cylinder engines (or thumpers ) are common for motorcycles and other small engines found in light machinery. On
1957-422: A separate ICE as an auxiliary power unit . Wankel engines are fitted to many unmanned aerial vehicles . ICEs drive large electric generators that power electrical grids. They are found in the form of combustion turbines with a typical electrical output in the range of some 100 MW. Combined cycle power plants use the high temperature exhaust to boil and superheat water steam to run a steam turbine . Thus,
2060-481: A separate blower avoids many of the shortcomings of crankcase scavenging, at the expense of increased complexity which means a higher cost and an increase in maintenance requirement. An engine of this type uses ports or valves for intake and valves for exhaust, except opposed piston engines , which may also use ports for exhaust. The blower is usually of the Roots-type but other types have been used too. This design
2163-416: A separate crankcase ventilation system. The cylinder head is attached to the engine block by numerous bolts or studs . It has several functions. The cylinder head seals the cylinders on the side opposite to the pistons; it contains short ducts (the ports ) for intake and exhaust and the associated intake valves that open to let the cylinder be filled with fresh air and exhaust valves that open to allow
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#17327810031072266-406: A single carburetor shared between all of the cylinders, though some high-performance engines historically had multiple carburetors. The carburetor works on Bernoulli's principle : the static pressure of the intake air reduces at higher speeds, drawing more fuel into the airstream. In most cases (except for the accelerator pump ), the driver pressing the throttle pedal does not directly increase
2369-405: Is a fly-back system, using interruption of electrical primary system current through some type of synchronized interrupter. The interrupter can be either contact points or a power transistor. The problem with this type of ignition is that as RPM increases the availability of electrical energy decreases. This is especially a problem, since the amount of energy needed to ignite a more dense fuel mixture
2472-421: Is also why diesel and HCCI engines are more susceptible to cold-starting issues, although they run just as well in cold weather once started. Light duty diesel engines with indirect injection in automobiles and light trucks employ glowplugs (or other pre-heating: see Cummins ISB#6BT ) that pre-heat the combustion chamber just before starting to reduce no-start conditions in cold weather. Most diesels also have
2575-503: Is commonplace in CI engines, and has been occasionally used in SI engines. CI engines that use a blower typically use uniflow scavenging . In this design the cylinder wall contains several intake ports placed uniformly spaced along the circumference just above the position that the piston crown reaches when at BDC. An exhaust valve or several like that of 4-stroke engines is used. The final part of
2678-542: Is driven downward with power, it first uncovers the exhaust port where the burned fuel is expelled under high pressure and then the intake port where the process has been completed and will keep repeating. Later engines used a type of porting devised by the Deutz company to improve performance. It was called the Schnurle Reverse Flow system. DKW licensed this design for all their motorcycles. Their DKW RT 125
2781-415: Is held in place relative to the engine block by main bearings , which allow it to rotate. Bulkheads in the crankcase form a half of every main bearing; the other half is a detachable cap. In some cases a single main bearing deck is used rather than several smaller caps. A connecting rod is connected to offset sections of the crankshaft (the crankpins ) in one end and to the piston in the other end through
2884-415: Is held shut by engine vacuum, is often used to do so. As the airflow through the carburetor increases the reduced manifold vacuum pulls the power valve open, allowing more fuel into the main metering circuit. In a two-stroke engine , the carburetor power valve operates in the opposite manner: in most circumstances the valve allows extra fuel into the engine, then at a certain engine RPM it closes to reduce
2987-406: Is higher. The result was often a high RPM misfire. Capacitor discharge ignition was developed. It produces a rising voltage that is sent to the spark plug. CD system voltages can reach 60,000 volts. CD ignitions use step-up transformers . The step-up transformer uses energy stored in a capacitance to generate electric spark . With either system, a mechanical or electrical control system provides
3090-400: Is limited mainly by the fuel's viscosity so that the fuel flow tends to be proportional to the pressure difference. So jets sized for full power tend to starve the engine at lower speed and part throttle. Most commonly this has been corrected by using multiple jets. In SU and other (e.g. Zenith-Stromberg ) variable jet carburetors, it was corrected by varying the jet size. The orientation of
3193-445: Is not possible to dedicate a stroke exclusively for each of them. Starting at TDC the cycle consists of: While a 4-stroke engine uses the piston as a positive displacement pump to accomplish scavenging taking 2 of the 4 strokes, a 2-stroke engine uses the last part of the power stroke and the first part of the compression stroke for combined intake and exhaust. The work required to displace the charge and exhaust gases comes from either
Carburetor - Misplaced Pages Continue
3296-404: Is often used to prevent icing. This system consists of a secondary air intake which passes around the exhaust, in order to heat the air before it enters the carburetor. Typically, the system is operated by the pilot manually switching the intake air to travel via the heated intake path as required. The carburetor heat system reduces the power output (due to the lower density of heated air) and causes
3399-660: Is spelled "carburetor" in American English and "carburettor" in British English . Colloquial abbreviations include carb in the UK and North America or Carby in Australia. Air from the atmosphere enters the carburetor (usually via an air cleaner ), has fuel added within the carburetor, passes into the inlet manifold , then through the inlet valve(s) , and finally into the combustion chamber . Most engines use
3502-514: Is the Wärtsilä-Sulzer RTA96-C turbocharged 2-stroke diesel, used in large container ships. It is the most efficient and powerful reciprocating internal combustion engine in the world with a thermal efficiency over 50%. For comparison, the most efficient small four-stroke engines are around 43% thermally-efficient (SAE 900648); size is an advantage for efficiency due to the increase in the ratio of volume to surface area. See
3605-399: Is used to compensate for the reduced vacuum that occurs when the throttle is opened, thus smoothing the transition from the idle circuit to the main metering circuit. In a four-stroke engine it is often desirable to provide extra fuel to the engine at high loads (to increase the power output and reduce engine knocking ). A 'power valve', which is a spring-loaded valve in the carburetor that
3708-539: The Carter Carburetor WCFB and the identical Rochester 4GC, introduced in various General Motors models for 1952. Oldsmobile referred the new carburetor as the "Quadri-Jet" (original spelling) while Buick called it the "Airpower". In the United States, carburetors were the common method of fuel delivery for most US-made gasoline (petrol) engines until the late 1980s, when fuel injection became
3811-611: The Otto engine , was created in 1876 by Nicolaus Otto . The term internal combustion engine usually refers to an engine in which combustion is intermittent , such as the more familiar two-stroke and four-stroke piston engines, along with variants, such as the six-stroke piston engine and the Wankel rotary engine . A second class of internal combustion engines use continuous combustion: gas turbines , jet engines and most rocket engines , each of which are internal combustion engines on
3914-618: The Pyréolophore , which was granted a patent by Napoleon Bonaparte . This engine powered a boat on the Saône river in France. In the same year, Swiss engineer François Isaac de Rivaz invented a hydrogen-based internal combustion engine and powered the engine by electric spark. In 1808, De Rivaz fitted his invention to a primitive working vehicle – "the world's first internal combustion powered automobile". In 1823, Samuel Brown patented
4017-432: The combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high- temperature and high- pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons ( piston engine ), turbine blades ( gas turbine ),
4120-473: The external links for an in-cylinder combustion video in a 2-stroke, optically accessible motorcycle engine. Dugald Clerk developed the first two-cycle engine in 1879. It used a separate cylinder which functioned as a pump in order to transfer the fuel mixture to the cylinder. In 1899 John Day simplified Clerk's design into the type of 2 cycle engine that is very widely used today. Day cycle engines are crankcase scavenged and port timed. The crankcase and
4223-414: The 1970s. EEC legislation required all vehicles sold and produced in member countries to have a catalytic converter after December 1992. This legislation had been in the pipeline for some time, with many cars becoming available with catalytic converters or fuel injection from around 1990. A significant concern for aircraft engines is the formation of ice inside the carburetor. The temperature of air within
Carburetor - Misplaced Pages Continue
4326-619: The Wankel design are used in some automobiles, aircraft and motorcycles. These are collectively known as internal-combustion-engine vehicles (ICEV). Where high power-to-weight ratios are required, internal combustion engines appear in the form of combustion turbines , or sometimes Wankel engines. Powered aircraft typically use an ICE which may be a reciprocating engine. Airplanes can instead use jet engines and helicopters can instead employ turboshafts ; both of which are types of turbines. In addition to providing propulsion, aircraft may employ
4429-412: The air speed through the venturi is insufficient to maintain the fuel flow, therefore the fuel is instead supplied by the carburetor's idle and off-idle circuits . At greater throttle openings, the speed of air passing through the venturi increases, which lowers the pressure of the air and draws more fuel into the airstream. At the same time, the reduced manifold vacuum results in less fuel flow through
4532-489: The associated process. While an engine is in operation, the crankshaft rotates continuously at a nearly constant speed . In a 4-stroke ICE, each piston experiences 2 strokes per crankshaft revolution in the following order. Starting the description at TDC, these are: The defining characteristic of this kind of engine is that each piston completes a cycle every crankshaft revolution. The 4 processes of intake, compression, power and exhaust take place in only 2 strokes so that it
4635-450: The barrels consist of "primary" barrel(s) used for lower load situations and secondary barrel(s) activating when required to provide additional air/fuel at higher loads. The primary and secondary venturi are often sized differently and incorporate different features to suit the situations in which they are used. Many four-barrel carburetors use two primary and two secondary barrels. A four-barrel design of two primary and two secondary barrels
4738-419: The carburetor can be reduced by up to 40 °C (72 °F), due to a combination of the reduced air pressure in the venturi and the latent heat of the evaporating fuel. The conditions during the descent to landing are particularly conducive to icing, since the engine is run at idle for a prolonged period with the throttle closed. Icing can also occur in cruise conditions at altitude. A carburetor heat system
4841-548: The carburetor is a key design consideration. Older engines used updraft carburetors, where the air enters from below the carburetor and exits through the top. From the late 1930s, downdraft carburetors become more commonly used (especially in the United States), along with side draft carburetors (especially in Europe). The main metering circuit consists of a pipe which reduces to a narrows before widening again, forming
4944-466: The choke based on the temperature of the engine's coolant liquid, an electrical resistance heater to do so, or air drawn through a tube connected to an engine exhaust source. A choke left closed after the engine has warmed up increases the engine's fuel consumption and exhaust gas emissions, and causes the engine to run rough and lack power due to an over-rich fuel mixture. However, excessive fuel can flood an engine and prevent it from starting. To remove
5047-619: The combustion gases to escape. The valves are often poppet valves but they can also be rotary valves or sleeve valves . However, 2-stroke crankcase scavenged engines connect the gas ports directly to the cylinder wall without poppet valves; the piston controls their opening and occlusion instead. The cylinder head also holds the spark plug in the case of spark ignition engines and the injector for engines that use direct injection. All CI (compression ignition) engines use fuel injection, usually direct injection but some engines instead use indirect injection . SI (spark ignition) engines can use
5150-455: The compressed air and combustion products and slide continuously within it while the engine is in operation. In smaller engines, the pistons are made of aluminum; while in larger applications, they are typically made of cast iron. In performance applications, pistons can also be titanium or forged steel for greater strength. The top surface of the piston is called its crown and is typically flat or concave. Some two-stroke engines use pistons with
5253-432: The compressed charge, four-cycle engine. In 1879, Karl Benz patented a reliable two-stroke gasoline engine. Later, in 1886, Benz began the first commercial production of motor vehicles with an internal combustion engine, in which a three-wheeled, four-cycle engine and chassis formed a single unit. In 1892, Rudolf Diesel developed the first compressed charge, compression ignition engine. In 1926, Robert Goddard launched
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#17327810031075356-404: The compression-based combustion of diesel requires the greater precision and pressure of fuel-injection. The name "carburetor" is derived from the verb carburet , which means "to combine with carbon", or, in particular, "to enrich a gas by combining it with carbon or hydrocarbons ". Thus a carburetor mixes intake air with hydrocarbon-based fuel, such as petrol or AutoGas (LPG). The name
5459-410: The corresponding ports. The intake manifold connects to the air filter directly, or to a carburetor when one is present, which is then connected to the air filter . It distributes the air incoming from these devices to the individual cylinders. The exhaust manifold is the first component in the exhaust system . It collects the exhaust gases from the cylinders and drives it to the following component in
5562-400: The crankcase or a separate blower. For scavenging, expulsion of burned gas and entry of fresh mix, two main approaches are described: Loop scavenging, and Uniflow scavenging. SAE news published in the 2010s that 'Loop Scavenging' is better under any circumstance than Uniflow Scavenging. Some SI engines are crankcase scavenged and do not use poppet valves. Instead, the crankcase and the part of
5665-401: The crankcase pressure is slightly below intake pressure, to let it be filled with a new charge; this happens when the piston is moving upwards. When the piston is moving downwards the pressure in the crankcase increases and the reed valve closes promptly, then the charge in the crankcase is compressed. When the piston is moving downwards, it also uncovers the exhaust port and the transfer port and
5768-413: The crankcase to the port in the cylinder to provide for intake and another from the exhaust port to the exhaust pipe. The height of the port in relationship to the length of the cylinder is called the "port timing". On the first upstroke of the engine there would be no fuel inducted into the cylinder as the crankcase was empty. On the downstroke, the piston now compresses the fuel mix, which has lubricated
5871-431: The cylinder below the piston is used as a pump. The intake port is connected to the crankcase through a reed valve or a rotary disk valve driven by the engine. For each cylinder, a transfer port connects in one end to the crankcase and in the other end to the cylinder wall. The exhaust port is connected directly to the cylinder wall. The transfer and exhaust port are opened and closed by the piston. The reed valve opens when
5974-411: The cylinder block has fins protruding away from it to cool the engine by directly transferring heat to the air. The cylinder walls are usually finished by honing to obtain a cross hatch , which is able to retain more oil. A too rough surface would quickly harm the engine by excessive wear on the piston. The pistons are short cylindrical parts which seal one end of the cylinder from the high pressure of
6077-407: The cylinder. Because there is no obstruction in the cylinder of the fuel to move directly out of the exhaust port prior to the piston rising far enough to close the port, early engines used a high domed piston to slow down the flow of fuel. Later the fuel was "resonated" back into the cylinder using an expansion chamber design. When the piston rose close to TDC, a spark ignited the fuel. As the piston
6180-414: The cylinder. At low rpm, the spark is timed to occur close to the piston achieving top dead center. In order to produce more power, as rpm rises the spark is advanced sooner during piston movement. The spark occurs while the fuel is still being compressed progressively more as rpm rises. The necessary high voltage, typically 10,000 volts, is supplied by an induction coil or transformer. The induction coil
6283-413: The early engines which used Hot Tube ignition. When Bosch developed the magneto it became the primary system for producing electricity to energize a spark plug. Many small engines still use magneto ignition. Small engines are started by hand cranking using a recoil starter or hand crank. Prior to Charles F. Kettering of Delco's development of the automotive starter all gasoline engined automobiles used
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#17327810031076386-453: The efficiency is higher because more energy is extracted from the fuel than what could be extracted by the combustion engine alone. Combined cycle power plants achieve efficiencies in the range of 50–60%. In a smaller scale, stationary engines like gas engines or diesel generators are used for backup or for providing electrical power to areas not connected to an electric grid . Small engines (usually 2‐stroke gasoline/petrol engines) are
6489-483: The engine in steady-state conditions, the inertia of fuel (being higher than that of air) causes a temporary shortfall as the throttle is opened. Therefore, an accelerator pump is often used to briefly provide extra fuel as the throttle is opened. When the driver presses the throttle pedal, a small piston or diaphragm pump injects extra fuel directly into the carburetor throat. The accelerator pump can also be used to "prime" an engine with extra fuel prior to attempting
6592-543: The engine is off. The battery also supplies electrical power during rare run conditions where the alternator cannot maintain more than 13.8 volts (for a common 12 V automotive electrical system). As alternator voltage falls below 13.8 volts, the lead-acid storage battery increasingly picks up electrical load. During virtually all running conditions, including normal idle conditions, the alternator supplies primary electrical power. Some systems disable alternator field (rotor) power during wide-open throttle conditions. Disabling
6695-418: The excess fuel, many carburetors with automatic chokes allow it to be held open (by manually, depressing the accelerator pedal to the floor and briefly holding it there while cranking the starter) to allow extra air into the engine until the excess fuel is cleared out. Another method used by carburetors to improve the operation of a cold engine is a fast idle cam , which is connected to the choke and prevents
6798-435: The field reduces alternator pulley mechanical loading to nearly zero, maximizing crankshaft power. In this case, the battery supplies all primary electrical power. Gasoline engines take in a mixture of air and gasoline and compress it by the movement of the piston from bottom dead center to top dead center when the fuel is at maximum compression. The reduction in the size of the swept area of the cylinder and taking into account
6901-623: The first internal combustion engine to be applied industrially. In 1854, in the UK, the Italian inventors Eugenio Barsanti and Felice Matteucci obtained the certification: "Obtaining Motive Power by the Explosion of Gases". In 1857 the Great Seal Patent Office conceded them patent No.1655 for the invention of an "Improved Apparatus for Obtaining Motive Power from Gases". Barsanti and Matteucci obtained other patents for
7004-595: The first liquid-fueled rocket. In 1939, the Heinkel He 178 became the world's first jet aircraft . At one time, the word engine (via Old French , from Latin ingenium , "ability") meant any piece of machinery —a sense that persists in expressions such as siege engine . A "motor" (from Latin motor , "mover") is any machine that produces mechanical power . Traditionally, electric motors are not referred to as "engines"; however, combustion engines are often referred to as "motors". (An electric engine refers to
7107-433: The float chamber is located close to the engine, heat from the engine (including for several hours after the engine is shut off) can cause the fuel to heat up to the point of vaporization. This causes air bubbles in the fuel (similar to the air bubbles that necessitate brake bleeding ), which prevents the flow of fuel and is known as 'vapor lock'. To avoid pressurizing the float chamber, vent tubes allow air to enter and exit
7210-407: The float chamber. These tubes usually extend into the carburetor throat, placed to prevent fuel from sloshing out of them into the carburetor. If an engine must be operated when the carburetor is not in an upright orientation (for example in a chainsaw or airplane), a float chamber and gravity activated float valve would not be suitable. Instead, a diaphragm chamber is typically used. This consists of
7313-414: The flow of air at the entrance to the carburetor. This increases the vacuum in the main metering circuit, causing more fuel to be supplied to the engine via the main jets. Prior to the late 1950s the choke was manually operated by the driver, often using a lever or knob on the dashboard . Since then, automatic chokes became more commonplace. These either use a bimetallic thermostat to automatically regulate
7416-604: The following conditions: The main advantage of 2-stroke engines of this type is mechanical simplicity and a higher power-to-weight ratio than their 4-stroke counterparts. Despite having twice as many power strokes per cycle, less than twice the power of a comparable 4-stroke engine is attainable in practice. In the US, 2-stroke engines were banned for road vehicles due to the pollution. Off-road only motorcycles are still often 2-stroke but are rarely road legal. However, many thousands of 2-stroke lawn maintenance engines are in use. Using
7519-426: The fuel entering the engine. Instead, the airflow through the carburetor increases, which in turn increases the amount of fuel drawn into the intake mixture. The main disadvantage of basing a carburetor's operation on Bernoulli's 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. The fuel jets are much smaller and fuel flow
7622-465: The fuel entering the engine. This is done in order to extend the engine's maximum RPM, since many two-stroke engines can temporarily achieve higher RPM with a leaner air-fuel ratio. This is not to be confused with the unrelated exhaust power valve arrangements used on two-stroke engines. A metering rod or step-up rod system is sometimes used as an alternative to a power valve in a four-stroke engine in order to supply extra fuel at high loads. One end of
7725-517: The gudgeon pin and thus transfers the force and translates the reciprocating motion of the pistons to the circular motion of the crankshaft. The end of the connecting rod attached to the gudgeon pin is called its small end, and the other end, where it is connected to the crankshaft, the big end. The big end has a detachable half to allow assembly around the crankshaft. It is kept together to the connecting rod by removable bolts. The cylinder head has an intake manifold and an exhaust manifold attached to
7828-505: The high temperature and pressure created by the engine in its compression process. The compression level that occurs is usually twice or more than a gasoline engine. Diesel engines take in air only, and shortly before peak compression, spray a small quantity of diesel fuel into the cylinder via a fuel injector that allows the fuel to instantly ignite. HCCI type engines take in both air and fuel, but continue to rely on an unaided auto-combustion process, due to higher pressures and temperature. This
7931-416: The higher pressure of the charge in the crankcase makes it enter the cylinder through the transfer port, blowing the exhaust gases. Lubrication is accomplished by adding two-stroke oil to the fuel in small ratios. Petroil refers to the mix of gasoline with the aforesaid oil. This kind of 2-stroke engine has a lower efficiency than comparable 4-strokes engines and releases more polluting exhaust gases for
8034-451: The highest thermal efficiencies among internal combustion engines of any kind. Some diesel–electric locomotive engines operate on the 2-stroke cycle. The most powerful of them have a brake power of around 4.5 MW or 6,000 HP . The EMD SD90MAC class of locomotives are an example of such. The comparable class GE AC6000CW , whose prime mover has almost the same brake power, uses a 4-stroke engine. An example of this type of engine
8137-424: The idle and off-idle circuits. During cold weather fuel vaporizes less readily and tends to condense on the walls of the intake manifold, starving the cylinders of fuel and making cold starts difficult. Additional fuel is required (for a given amount of air) to start and run the engine until it warms up, provided by a choke valve . While the engine is warming up the choke valve is partially closed, restricting
8240-407: The intake air filter to be bypassed, therefore the system is only used when there is a risk of icing. If the engine is operating at idle RPM, another method to prevent icing is to periodically open the throttle, which increases the air temperature within the carburetor. Carburetor icing also occurs on other applications and various methods have been employed to solve this problem. On inline engines
8343-410: The intake air travelling through the carburetor is pressurized (such as where the carburetor is downstream of a supercharger ) the entire carburetor must be contained in an airtight pressurized box to operate. However, this is not necessary where the carburetor is upstream of the supercharger. Problems of fuel boiling and vapor lock can occur in carbureted engines, especially in hotter climates. Since
8446-490: The intake and exhaust manifolds are on the same side of the head. Heat from the exhaust is used to warm the intake manifold and in turn the carburetor. On V configurations, exhaust gases were directed from one head through the intake cross over to the other head. One method for regulating the exhaust flow on the cross over for intake warming was a weighted eccentric butterfly valve called a heat riser that remained closed at idle and opened at higher exhaust flow. Some vehicles used
8549-419: The intake manifold is an air sleeve that feeds the intake ports. The intake ports are placed at a horizontal angle to the cylinder wall (I.e: they are in plane of the piston crown) to give a swirl to the incoming charge to improve combustion. The largest reciprocating IC are low speed CI engines of this type; they are used for marine propulsion (see marine diesel engine ) or electric power generation and achieve
8652-429: The inventor of the diesel engine, Rudolf Diesel , was using peanut oil to run his engines. Renewable fuels are commonly blended with fossil fuels. Hydrogen , which is rarely used, can be obtained from either fossil fuels or renewable energy. Various scientists and engineers contributed to the development of internal combustion engines. In 1791, John Barber developed the gas turbine . In 1794 Thomas Mead patented
8755-480: The needle valve to admit more fuel, allowing the engine to generate more power. A balanced state is reached which creates a steady fuel reservoir level, that remains constant in any orientation. Other components that have been used on carburetors include: The basic design for a carburetor consists of a single venturi (main metering circuit), though designs with two or four venturi (two-barrel and four-barrel carburetors respectively) are also quite commonplace. Typically
8858-407: The oil into the combustion chamber. A ventilation system drives the small amount of gas that escapes past the pistons during normal operation (the blow-by gases) out of the crankcase so that it does not accumulate contaminating the oil and creating corrosion. In two-stroke gasoline engines the crankcase is part of the air–fuel path and due to the continuous flow of it, two-stroke engines do not need
8961-402: The outer side of the cylinder, passages that contain cooling fluid are cast into the engine block whereas, in some heavy duty engines, the passages are the types of removable cylinder sleeves which can be replaceable. Water-cooled engines contain passages in the engine block where cooling fluid circulates (the water jacket ). Some small engines are air-cooled, and instead of having a water jacket
9064-460: The part of the cylinder below the exhaust port is used as a pump. The operation of the Day cycle engine begins when the crankshaft is turned so that the piston moves from BDC upward (toward the head) creating a vacuum in the crankcase/cylinder area. The carburetor then feeds the fuel mixture into the crankcase through a reed valve or a rotary disk valve (driven by the engine). There are cast in ducts from
9167-427: The path. The exhaust system of an ICE may also include a catalytic converter and muffler . The final section in the path of the exhaust gases is the tailpipe . The top dead center (TDC) of a piston is the position where it is nearest to the valves; bottom dead center (BDC) is the opposite position where it is furthest from them. A stroke is the movement of a piston from TDC to BDC or vice versa, together with
9270-412: The piston in the cylinder and the bearings due to the fuel mix having oil added to it. As the piston moves downward it first uncovers the exhaust, but on the first stroke there is no burnt fuel to exhaust. As the piston moves downward further, it uncovers the intake port which has a duct that runs to the crankcase. Since the fuel mix in the crankcase is under pressure, the mix moves through the duct and into
9373-409: The power wasting in overcoming friction , or to make the mechanism work at all. Also, the lubricant used can reduce excess heat and provide additional cooling to components. At the very least, an engine requires lubrication in the following parts: In 2-stroke crankcase scavenged engines, the interior of the crankcase, and therefore the crankshaft, connecting rod and bottom of the pistons are sprayed by
9476-482: The preferred method. One of the last motorsport users of carburetors was NASCAR, which switched to electronic fuel injection after the 2011 Sprint Cup series . NASCAR still uses the four-barrel carburetor in the NASCAR Xfinity Series . In Europe, carburetors were largely replaced by fuel injection in the late 1980s, although fuel injection had been increasingly used in luxury cars and sports cars since
9579-403: The primary power supply for vehicles such as cars , aircraft and boats . ICEs are typically powered by hydrocarbon -based fuels like natural gas , gasoline , diesel fuel , or ethanol . Renewable fuels like biodiesel are used in compression ignition (CI) engines and bioethanol or ETBE (ethyl tert-butyl ether) produced from bioethanol in spark ignition (SI) engines. As early as 1900
9682-497: The rods is tapered, which sits in the main metering jets and acts as a valve for fuel flow in the jets. At high engine loads, the rods are lifted away from the jets (either mechanically or using manifold vacuum), increasing the volume of fuel can flow through the jet. These systems have been used by the Rochester Quadra jet and in the 1950s Carter carburetors. While the main metering circuit can adequately supply fuel to
9785-452: The same invention in France, Belgium and Piedmont between 1857 and 1859. In 1860, Belgian engineer Jean Joseph Etienne Lenoir produced a gas-fired internal combustion engine. In 1864, Nicolaus Otto patented the first atmospheric gas engine. In 1872, American George Brayton invented the first commercial liquid-fueled internal combustion engine. In 1876, Nicolaus Otto began working with Gottlieb Daimler and Wilhelm Maybach , patented
9888-684: The same principle as previously described. ( Firearms are also a form of internal combustion engine, though of a type so specialized that they are commonly treated as a separate category, along with weaponry such as mortars and anti-aircraft cannons.) In contrast, in external combustion engines , such as steam or Stirling engines , energy is delivered to a working fluid not consisting of, mixed with, or contaminated by combustion products. Working fluids for external combustion engines include air, hot water, pressurized water or even boiler -heated liquid sodium . While there are many stationary applications, most ICEs are used in mobile applications and are
9991-400: The stem of the valve or may act upon a rocker arm , again, either directly or through a pushrod . The crankcase is sealed at the bottom with a sump that collects the falling oil during normal operation to be cycled again. The cavity created between the cylinder block and the sump houses a crankshaft that converts the reciprocating motion of the pistons to rotational motion. The crankshaft
10094-399: The throttle from closing fully while the choke is in operation. The resulting increase in idle speed provides a more stable idle for a cold engine (by better atomizing the cold fuel) and helps the engine warm up quicker. The system within a carburetor that meters fuel when the engine is running at low RPM. The idle circuit is generally activated by vacuum under the throttle plate, which causes
10197-542: The top of a vessel containing the fuel. The first float-fed carburetor design, which used an atomizer nozzle , was introduced by German engineers Wilhelm Maybach and Gottlieb Daimler in their 1885 Grandfather Clock engine . The Butler Petrol Cycle car—built in England in 1888—also used a float-fed carburetor. The first carburetor for a stationary engine was patented in 1893 by Hungarian engineers János Csonka and Donát Bánki . The first four-barrel carburetors were
10300-423: The volume of the combustion chamber is described by a ratio. Early engines had compression ratios of 6 to 1. As compression ratios were increased, the efficiency of the engine increased as well. With early induction and ignition systems the compression ratios had to be kept low. With advances in fuel technology and combustion management, high-performance engines can run reliably at 12:1 ratio. With low octane fuel,
10403-549: The world, the oil was actually drained and heated overnight and returned to the engine for cold starts. In the early 1950s, the gasoline Gasifier unit was developed, where, on cold weather starts, raw gasoline was diverted to the unit where part of the fuel was burned causing the other part to become a hot vapor sent directly to the intake valve manifold. This unit was quite popular until electric engine block heaters became standard on gasoline engines sold in cold climates. For ignition, diesel, PPC and HCCI engines rely solely on
10506-529: Was commonly used in V8 engines to conserve fuel at low engine speeds while still affording an adequate supply at high. The use of multiple carburetors (e.g., a carburetor for each cylinder or pair of cylinders) also results in the intake air being drawn through multiple venturi. Some high-performance engines have used multiple two-barrel or four-barrel carburetors, for example six two-barrel carburetors on Ferrari V12s. In 1826, American engineer Samuel Morey received
10609-405: Was one of the first motor vehicles to achieve over 100 mpg as a result. Internal combustion engines require ignition of the mixture, either by spark ignition (SI) or compression ignition (CI) . Before the invention of reliable electrical methods, hot tube and flame methods were used. Experimental engines with laser ignition have been built. The spark-ignition engine was a refinement of
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