92-612: Or 5.9L (360ci) LA V8, optional 4-barrel carburetor The XR311 was a prototype military vehicle of US origin that was procured in limited numbers during the 1970s. It was originally developed as the High Mobility Combat Vehicle , or HMCV (not to be confused with the JGSDF MCV , which was also called the "HMCV" for a short time). Development of the XR311 commenced as a private venture in 1969, with
184-424: A TOW missile installation for use in the anti-tank/AFV role, three had an M2HB machine-gun for use in the reconnaissance role and three had 7.62mm M60 machine guns and the crew armor kit for use in the escort/security role. These trials were completed in 1972. They were then tested by the 2nd Armored Division. In 1974 they were also tested in the 2nd Armored Reconnaissance Scout Vehicle competition along with
276-420: 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
368-424: A torsion-bar spring and hydraulic telescopic shock absorber at each station. A stabilizer bar is provided for the rear suspension to limit body roll. Maximum speed is 80–90 mph for vehicles with the 318ci engine, dropping to 67 mph at full load. Acceleration was 12 seconds 0–60 mph time, falling to 10 seconds with the 360ci engine. The steering is power-assisted and the tubeless tires feature
460-467: 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,
552-460: A "mud tire"). Disc brakes are fitted on all four wheels. The electrical system is 24V DC , and two batteries with a capacity of 45 Amp/Hr are provided. The alternator is of the integral rectifier and regulator type. The XR311 is provided with a heavy duty towing pintle as well as a trailer wiring harness receptacle. It is air-transportable and can be air-dropped . Carburetor A carburetor (also spelled carburettor or carburetter )
644-412: A 5.89:1 drive ratio are used front and rear, and a lockable center differential ensures traction to all wheels. The fully independent suspension uses modified Dana 44 centersections, and used many off the shelf parts from the front wheel drive Oldsmobile Toronado / Cadillac Eldorado (e.g., CV joints and boots, spindle and bearings, and 11-inch disk brakes), and is of a double-wishbone design with
736-527: A Grand Prix racing car for the Auto Union company. The high power of the design caused one of the rear wheels to experience excessive wheel spin at any speed up to 160 km/h (100 mph). In 1935, Porsche commissioned the engineering firm ZF to design a limited-slip differential to improve performance. The ZF "sliding pins and cams" became available, and one example was the Type B-70 used during
828-403: A case with a standard differential, the slipping or non-contacting wheel will receive the majority of the power (in the form of low-torque, high-rpm rotation), while the contacting wheel will remain stationary with respect to the ground. The torque transmitted by an open differential will always be equal at both wheels; if one tire is on a slippery surface, the supplied torque will easily overcome
920-591: A clutch-type limited-slip differential under the Twin Traction trademark, promoting it as an aid for driving in severe winter weather. In 1957, General Motors (GM) introduced a competing system for Chevrolet branded vehicles under the Positraction name. Within a few years, other American automotive brands introduced similar systems under a variety of names, including Safe-T-Track for GM's Pontiac brand and Anti Spin for its Oldsmobile brand, while
1012-426: A cylindrical chamber of fluid filled with a stack of perforated discs rotates with the normal motion of the output shafts. The inside surface of the chamber is coupled to one of the driveshafts, and the outside coupled to the differential carrier. Half of the discs are connected to the inner, the other half to the outer, alternating inner/outer in the stack. Differential motion forces the interleaved discs to move through
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#17327879703101104-429: 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
1196-475: 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. Limited-slip differential A limited-slip differential ( LSD ) is a type of differential gear train that allows its two output shafts to rotate at different speeds but limits
1288-440: 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
1380-414: A maximum load of 386 kg (851 lb). The minimum ground clearance is 11 inches, and a full length skid pan protects the hull and drivetrain, which allows the vehicle to slide over obstacles. The transmission is a Chrysler A-727 " TorqueFlite " torque converter automatic , with three forward and one reverse gears. The XR311 is a full-time 4WD vehicle . "Trak-lok" limited-slip differentials with
1472-428: A more complex torque-split and should be considered in the case when the outputs are spinning the same speed and when spinning at different speeds. The torque difference between the two axles is called Trq d . (In this work it is called Trq f for torque friction ). Trq d is the difference in torque delivered to the left and right wheel. The magnitude of Trq d comes from the slip-limiting mechanism in
1564-403: A mounting bracket on the hood until needed again. The passenger compartment is in the center of the vehicle with the driver on the left and the passenger seat to the right. There is space for 0.93 cubic metres (33 cu ft) of cargo behind the passenger seats. The engine and transmission are at the rear of the hull and there is an external load-carrying platform above this which can take
1656-468: A number of vehicles including the original FMC Technologies and Lockheed Martin designs. It has been stated that an XR311 with TOW missile installation cost around $ 50,000. The XR311 was designed to carry out a wide variety of roles including anti-tank, reconnaissance patrol , convoy escort, command and control , medivac , military police , mortar carrier, internal security and forward air defense communications vehicle. There were several models of
1748-464: 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
1840-415: A resisting torque between either the two outputs, or the outputs and the differential housing. There are many mechanisms used to create this resisting torque. Types of limited-slip differential typically are named from the type of the resisting mechanism. Examples include viscous and clutch-based LSDs. The amount of limiting torque provided by these mechanisms varies by design. A limited-slip differential has
1932-406: 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
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#17327879703102024-418: A special high-pressure inner tire tube, which provides a built-in backup in case air pressure is lost from the main tire itself, as well as providing lateral support to eliminate leakage from the tire bead during high speed cornering. The tires are self-cleaning, meaning mud and other materials are flung free from the tread grooves by centrifugal force, rather than sticking to the tire (more commonly known as
2116-467: A traditional limited-slip differential. The systems harness various chassis sensors such as speed sensors, anti-lock braking system (ABS) sensors, accelerometers , and microcomputers to electronically monitor wheel slip and vehicle motion. When the chassis control system determines a wheel is slipping, the computer applies the brakes to that wheel. A significant difference between the limited-slip differential systems listed above and this brake-based system,
2208-534: Is statically indeterminate but is in the range of ½ Trq in ±( ½ Trq d ) . Several types of LSD are commonly used in passenger cars. In this differential the maximum torque difference between the two outputs, Trq d , is a fixed value at all times regardless of torque input to the differential or speed difference between the two outputs. Typically this differential used spring-loaded clutch assemblies. These limited-slip differentials use helical gears, clutches or cones (an alternative type of clutch) where
2300-518: Is a completely separate design from the most common beveled spider gear designs seen in most automotive applications. As torque is applied to the gears, they are pushed against the walls of the differential housing, creating friction. The friction resists the relative movement of the outputs and creates the limiting torque Trq d . Unlike other friction-based LSD designs that combine a common spider gear "open" differential in combination with spring-loaded friction components that inhibit differentiation,
2392-753: 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
2484-448: Is a significant speed difference between the right and left wheel, and internal damping to avoid hysteresis . The newest gerotor pump based system has computer regulated output for more versatility and no oscillation. An electronic limited-slip differential will typically have a planetary or bevel gear set similar to that of an open differential and a clutch pack similar to that in a torque sensitive or gerotor pump based differential. In
2576-452: Is applied in the opposite direction it behaves like an open differential. In the case of a FWD car it is argued to be safer than a 2-way differential. The argument is if there is no additional coupling on over run, i.e. a 1-way LSD as soon as the driver lifts the throttle, the LSD unlocks and behaves somewhat like a conventional open differential. This is also the best for FWD cars, as it allows
2668-510: Is built around a tubular-steel frame safety roll-cage which protects the passenger compartment if the vehicle rolls over. This cage is covered by a heavy-gauge sheet metal forming the skin of the vehicle. An internally mounted electrical extraction winch with a capacity of 5,000 kg (11,023 lb) can be mounted at the front of the vehicle if required, and the 2-piece windshield can be removed to provide greater visibility and protect from flying glass fragments. The glass halves are stored in
2760-421: Is designed to function in this manner, which was promoted to provide a different benefit: if one rear drive wheel momentarily leaves the ground when it hits a bump with the differential under load, the airborne wheel will not spin freely and cause the vehicle to break traction when the spinning wheel touches the ground again. A 1-way differential will provide its limiting action in only one direction. When torque
2852-550: Is far less than is required to move the vehicle. Meanwhile, the tire on the slippery surface will simply spin, absorbing all of the actual power output (which is a function of torque provided over the course of revolutions), even though both wheels are provided the same (very low) amount of torque. In this situation, a limited-slip differential prevents excessive power from being allocated to one wheel, and so keeps both wheels in powered rotation. The advantages of LSD in high-power, rear-wheel drive automobiles were demonstrated during
FMC XR311 - Misplaced Pages Continue
2944-415: 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
3036-419: Is held stationary by being mounted to the vehicle frame). This coined the terms "one wheel peel" or "one tire fire". As such, "Muscle-Cars" with LSD or "posi" (positraction) had a distinct advantage to their wheel-spinning counterparts. Mechanical limited-slip differentials are considered essential to perform a proper drift . Both limited-slip differentials and open differentials have a gear train that allows
3128-400: 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
3220-405: 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
3312-664: 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
3404-462: Is that brake-based systems do not inherently send the greater torque to the slower wheel, plus the added brake friction material wear that results from the use of such a system if the vehicle is driven in an environment where the brake-based system will activate on a regular basis. BMW 's electronic limited-slip differential used on the F10 5 Series is an example of such a system. Another example began on
3496-735: Is the Porsche PSD system used on the Porsche 928 . An additional example is the SAAB XWD ( Haldex Generation 4) with eLSD, which uses a common (electronically controlled via the vehicle computer network) hydraulic power pack to control both the longitudinal and transversal torque transfer of the XWD system. The same Haldex system is used on several other GM Epsilon based vehicles such as the Cadillac SRX etc. These systems are alternatives to
3588-399: 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
3680-541: 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
3772-534: The Ford Motor Company introduced Traction-Lok for Ford vehicles and Directed Power for its Lincoln cars. Chrysler purchased Power-Lok units from Dana Incorporated and Spin-Resistant units from Borg-Warner , marketing both under the Sure-Grip name on Chrysler, Dodge , and Plymouth vehicles. Limited-slip differentials became very popular and sought after during the muscle car era in
FMC XR311 - Misplaced Pages Continue
3864-498: The 1960s and 1970s. Despite the myriad marketing names used by competing brands, the popularity of Chevrolet vehicles resulted in Positraction becoming a generic trademark in the U.S. for limited-slip differentials generally. The main advantage of a limited-slip differential is demonstrated by considering the case of a standard (or "open") differential in off-roading or snow situations where one wheel begins to slip. In such
3956-414: 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
4048-475: The 1992 film My Cousin Vinny , the proof of innocence of two young men falsely accused of murder relies heavily on a photograph of tire marks made by a car which has a limited-slip differential, which (as Marisa Tomei 's character famously declares in an Oscar -winning performance) "was not available on the '64 Buick Skylark ," the car driven by the defendants. She argues that the evidence proves, rather, that
4140-517: The Second World War in the military VWs ( Kübelwagen and Schwimmwagen ), although technically this was not a limited-slip differential, but a system composed of two freewheels , which sent the whole of the engine power to the slower-turning of the two wheels. Limited-slip differentials were widely introduced by U.S. automakers in the late 1950s and were marketed under a wide variety of trademarked names. In early 1956, Packard introduced
4232-419: The United States "Muscle-Car" era from the mid 1960s through the early 1970s. Cars of this era normally were rear-wheel drive and did not feature independent suspension for the rear tires (but instead used a live axle ). With a live axle, when high torque is applied through the differential, the traction on the right rear tire is lower as the axle naturally wants to turn with the torsion of the drive shaft (but
4324-770: The XR311: The following kits were available for the basic vehicle: crew compartment armor kit, consisting of a high-hardness steel doors, side body panels, toe panel, firewall, bulletproof windshield and bulletproof side windows, armored radiator, armored fuel tank, top and door kit (waterproof fabric with plastic windows and hinged doors) various communications installations, high output alternators (100 and 180 amp), litter-carrying kit, jump seat for two additional passengers, explosion-resistant reticulated foam fuel-tank filler, radial tires or foam-filled run-flat tires , extreme climate kits for winterization or desert temperatures, tool kit and portable fire extinguisher . The XR311
4416-413: 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
4508-421: The available traction at a very low number. For example, the right tire might begin to spin as soon as 70 N⋅m (50 lb⋅ft) of torque is placed on it, since it is on an icy surface. Since the same amount of torque is always felt at both wheels, regardless of the speed at which they are turning, this means that the wheel with traction cannot receive more than 70 N⋅m (50 lb⋅ft) of torque either, which
4600-450: 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
4692-572: The car to turn in on throttle release, instead of ploughing forward. A 1.5-way differential refers to one where the forward and reverse limiting torques, Trq d_fwd, d_rev , are different but neither is zero as in the case of the 1-way LSD. This type of differential is common in racing cars where a strong limiting torque can aid stability under engine braking. Geared, torque-sensitive mechanical limited-slip differentials use worm gears and spur gears to distribute and differentiate input power between two drive wheels or front and back axles. This
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#17327879703104784-420: 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
4876-548: 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
4968-466: 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
5060-408: 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
5152-534: The coupling is proportional to the input torque. With no load, the coupling is reduced to the static coupling. The behavior on over run (particularly sudden throttle release) determines whether the LSD is 1 way, 1.5 way, or 2 way. A 2-way differential will have the same limiting torque Trq d in both the forward and reverse directions. This means the differential will provide some level of limiting action under engine braking. The early Packard Twin Traction unit
5244-406: The differential and may be a function of input torque (as in the case of a gear differential), or the difference in the output speeds (as in the case of a viscous differential). The torque delivered to the outputs is: When traveling in a straight line, where one wheel starts to slip (and spin faster than the wheel with traction), torque is reduced to the slipping wheel ( Trq 2 ) and provided to
5336-565: The differential center, internal pressure rings (adjoining the clutch stack) are forced sideways by the pinion cross shaft trying to climb the ramp, which compresses the clutch stack. The more the clutch stack is compressed, the more coupled the wheels are. The mating of the vertical ramp (80–85° in practice to avoid chipping) surfaces in a one-way LSD on overrun produces no cam effect or corresponding clutch stack compression. Broadly speaking, there are three input torque states: load, no load, and over run. During load conditions, as previously stated,
5428-459: The differential. This is not serviceable; when the differential's behavior deteriorates, the VLSD center must be replaced. This style limited-slip differential works by using a gerotor pump to hydraulically compress a clutch to transfer torque to the wheel that is rotating slower. The gerotor pump uses the differential carrier or cage to drive the outer rotor of the pump and one axle shaft to drive
5520-447: The drive wheels are minimally coupled. The amount of preload (hence static coupling) on the clutches or cones is affected by the general condition (wear) and by how tightly they are loaded. The clutch type has a stack of thin clutch-discs, half of which are coupled to one of the drive shafts, the other half of which are coupled to the spider gear carrier. The clutch stacks may be present on both drive shafts, or on only one. If on only one,
5612-535: The electronic unit the clamping force on the clutch is controlled externally by a computer or other controller. This allows the control of the differential’s limiting torque, Trq d , to be controlled as part of a total chassis management system. An example of this type of differential is Subaru’s DCCD used in the Subaru WRX STi. The Jeep Quadra-Drive II four-wheel-drive system produced beginning in 2005 utilizes this type of differential. Another example
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#17327879703105704-593: The engagement force of the gears or clutch is a function of the input torque applied to the differential (as the engine applies more torque the gears or clutches grip harder and Trq d increases). Torque sensing LSDs respond to driveshaft torque, so that the more driveshaft input torque present, the harder the clutches, cones or gears are pressed together, and thus the more closely the drive wheels are coupled to each other. Some include spring loading to provide some small torque so that with little or no input torque (trailing throttle/gearbox in neutral/main clutch depressed)
5796-485: 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
5888-418: 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
5980-632: The first of two prototypes being completed in 1970. The vehicle was developed as a possible replacement for the by that time over ten years old M151 jeep , years prior to the Lamborghini Cheetah and other competitors, including AM General 's design for the HMMWV , which was eventually selected. As a result of the trials of these two prototypes the US Army purchased ten improved or second generation models in 1971. Of these ten vehicles, four had
6072-426: The first year (1992) production of the re-styled, and new 4.6L V-8 overhead cam Ford Crown Victoria model with its optional anti-lock brakes. This option was available on the 1992 Crown Victoria, onward; on those cars equipped with anti-lock brakes. In The Beach Boys ' song " 409 ", the lyrics mention the presence of a limited-slip differential: "...My four-speed, dual-quad, Positraction 4-0-9 (4-0-9, 4-0-9)." In
6164-433: 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
6256-407: 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
6348-414: 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
6440-431: The fluid against each other. In some viscous couplings when speed is maintained the fluid will accumulate heat due to friction. This heat will cause the fluid to expand, and expand the coupler causing the discs to be pulled together resulting in a non-viscous plate to plate friction and a dramatic drop in speed difference. This is known as the hump phenomenon and it allows the side of the coupler to gently lock. In contrast to
6532-426: 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
6624-465: 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
6716-424: 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
6808-405: The inner rotor. When there is a difference between the left and right wheels' speed, the pump pressurizes the hydraulic fluid causing the clutch to compress, thereby causing the torque to be transferred to the wheel that is rotating slower. These pump-based systems have lower and upper limits on applied pressure which allows the differential to work like a conventional or open differential until there
6900-409: 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
6992-411: 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
7084-490: 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
7176-462: The maximum difference between the two shafts. Limited-slip differentials are often known by the generic trademark Positraction , a brand name owned by General Motors and originally used for its Chevrolet branded vehicles. In an automobile, such limited-slip differentials are sometimes used in place of a standard differential, where they convey certain dynamic advantages, at the expense of greater complexity. In 1932, Ferdinand Porsche designed
7268-540: The mechanical type, the limiting action is much softer and more proportional to the slip, and so is easier to cope with for the average driver. New Process Gear used a viscous coupling of the Ferguson style in several of their transfer cases including those used in the AMC Eagle . Viscous LSDs are less efficient than mechanical types, that is, they "lose" some power. In particular, any sustained load which overheats
7360-480: 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
7452-419: The output shafts to spin at different speeds while holding the sum of their speeds proportional to that of the input shaft. Automotive limited-slip differentials have some type of mechanism that applies a torque (internal to the differential) that resists the relative motion of the output shafts. In simple terms, this means they have some mechanism which resists a speed difference between the outputs, by creating
7544-484: 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
7636-411: The ramps are symmetrical, the LSD is 2 way. If they are saw toothed (i.e. one side of the ramp is vertical), the LSD is 1 way. If both sides are sloped, but are asymmetric, the LSD is 1.5 way. An alternative is to use the natural separation force of the gear teeth to load the clutch. An example is the center differential of the 2011 Audi Quattro RS 5. As the input torque of the driveshaft tries to turn
7728-480: The remaining drive shaft is linked to the clutched drive shaft through the spider gears. In a cone type the clutches are replaced by a pair of cones which are pressed together achieving the same effect. One method for creating the clamping force is the use of a cam-ramp assembly such as used in a Salisbury/ramp style LSD. The spider gears mount on the pinion cross shaft which rests in angled cutouts forming cammed ramps. The cammed ramps are not necessarily symmetrical. If
7820-497: 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
7912-405: The silicone results in sudden permanent loss of the differential effect. They do have the virtue of failing gracefully, reverting to semi-open differential behavior. Typically a visco-differential that has covered 60,000 miles (97,000 km) or more will be functioning largely as an open differential. The silicone oil is factory sealed in a separate chamber from the gear oil surrounding the rest of
8004-421: The slower wheel ( Trq 1 ). In the case when the vehicle is turning and neither wheel is slipping, the inside wheel will be turning slower than the outside wheel. In this case the inside wheel will receive more torque than the outside wheel, which can result in understeer. When both wheels are spinning at the same speed, the torque distribution to each wheel is: This means the maximum torque to either wheel
8096-399: 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
8188-549: 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
8280-415: The torque bias sensing design is inherent in its design, not as an add-on, but is still an LSD type. The result is a differential that does not bind up like some LSD types and locking ones, but still gives increased power delivery under many road conditions. Examples include: Speed-sensitive differentials limit the torque difference between the outputs, Trq d , based on the difference in speed between
8372-454: The two output shafts. Thus for small output speed differences the differential’s behavior may be very close to an open differential. As the speed difference increases, the limiting torque increases. This results in different dynamic behavior as compared to a torque sensitive differential. The viscous type is generally simpler because it relies on hydrodynamic friction from fluids with high viscosity . Silicone -based oils are often used. Here,
8464-530: 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
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