Internal combustion engine cooling
Internal combustion engine cooling uses either air or liquid to remove the waste heat from an internal combustion engine. For small or special purpose engines, cooling using air from the atmosphere makes for a lightweight and simple system. Watercraft can use water directly from the surrounding environment to cool their engines. For water-cooled engines on aircraft and surface vehicles, waste heat is transferred from a closed loop of water pumped through the engine to the surrounding atmosphere by a radiator. Water has a higher heat capacity than air, can thus move heat more away from the engine, but a radiator and pumping system add weight and cost. Higher-power engines generate more waste heat, but can move more weight, meaning they are water-cooled. Radial engines allow air to flow around each cylinder directly, giving them an advantage for air cooling over straight engines, flat engines, V engines. Rotary engines have a similar configuration, but the cylinders continually rotate, creating an air flow when the vehicle is stationary.
Aircraft design more favors lower weight and air-cooled designs. Rotary engines were popular on aircraft until the end of World War I, but had serious stability and efficiency problems. Radial engines were popular until the end of World War II, until gas turbine engines replaced them. Modern propeller-driven aircraft with internal-combustion engines are still air-cooled. Modern cars favor power over weight, have water-cooled engines. Modern motorcycles are lighter than cars, both cooling fluids are common; some sport motorcycles were cooled with both oil. Heat engines generate mechanical power by extracting energy from heat flows, much as a water wheel extracts mechanical power from a flow of mass falling through a distance. Engines are inefficient, so more. Internal combustion engines remove waste heat through cool intake air, hot exhaust gases, explicit engine cooling. Engines with higher efficiency less as waste heat; some waste heat is essential: it guides heat through the engine, much as a water wheel works only if there is some exit velocity in the waste water to carry it away and make room for more water.
Thus, all heat engines need cooling to operate. Cooling is needed because high temperatures damage engine materials and lubricants and becomes more important in hot climates. Internal-combustion engines burn fuel hotter than the melting temperature of engine materials, hot enough to set fire to lubricants. Engine cooling removes energy fast enough to keep temperatures low; some high-efficiency engines run without explicit cooling and with only incidental heat loss, a design called adiabatic. Such engines can achieve high efficiency but compromise power output, duty cycle, engine weight and emissions. Most internal combustion engines are fluid cooled using either air or a liquid coolant run through a heat exchanger cooled by air. Marine engines and some stationary engines have ready access to a large volume of water at a suitable temperature; the water may be used directly to cool the engine, but has sediment, which can clog coolant passages, or chemicals, such as salt, that can chemically damage the engine.
Thus, engine coolant may be run through a heat exchanger, cooled by the body of water. Most liquid-cooled engines use a mixture of water and chemicals such as antifreeze and rust inhibitors; the industry term for the antifreeze mixture is engine coolant. Some antifreezes use no water at all, instead using a liquid with different properties, such as propylene glycol or a combination of propylene glycol and ethylene glycol. Most "air-cooled" engines use some liquid oil cooling, to maintain acceptable temperatures for both critical engine parts and the oil itself. Most "liquid-cooled" engines use some air cooling, with the intake stroke of air cooling the combustion chamber. An exception is Wankel engines, where some parts of the combustion chamber are never cooled by intake, requiring extra effort for successful operation. There are many demands on a cooling system. One key requirement is to adequately serve the entire engine, as the whole engine fails if just one part overheats. Therefore, it is vital.
Liquid-cooled engines are able to vary the size of their passageways through the engine block so that coolant flow may be tailored to the needs of each area. Locations with either high peak temperatures or high heat flow may require generous cooling; this reduces the occurrence of hot spots. Air-cooled engines may vary their cooling capacity by using more spaced cooling fins in that area, but this can make their manufacture difficult and expensive. Only the fixed parts of the engine, such as the block and head, are cooled directly by the main coolant system. Moving parts such as the pistons, to a lesser extent the crank and rods, must rely on the lubrication oil as a coolant, or to a limited amount of conduction into the block and thence the main coolant. High performance engines have additional oil, beyond the amount needed for lubrication, sprayed upwards onto the bottom of the piston just for extra cooling. Air-cooled motorcycles rely on oil-cooling in addition to air-cooling of the cylinder barrels.
Liquid-cooled engines have a circulation pump. The first engines relied
A turbocharger, colloquially known as a turbo, is a turbine-driven forced induction device that increases an internal combustion engine's efficiency and power output by forcing extra compressed air into the combustion chamber. This improvement over a aspirated engine's power output is due to the fact that the compressor can force more air—and proportionately more fuel—into the combustion chamber than atmospheric pressure alone. Turbochargers were known as turbosuperchargers when all forced induction devices were classified as superchargers. Today the term "supercharger" is applied only to mechanically driven forced induction devices; the key difference between a turbocharger and a conventional supercharger is that a supercharger is mechanically driven by the engine through a belt connected to the crankshaft, whereas a turbocharger is powered by a turbine driven by the engine's exhaust gas. Compared with a mechanically driven supercharger, turbochargers tend to be more efficient, but less responsive.
Twincharger refers to an engine with a turbocharger. Turbochargers are used on truck, train and construction equipment engines, they are most used with Otto cycle and Diesel cycle internal combustion engines. Forced induction dates from the late 19th century, when Gottlieb Daimler patented the technique of using a gear-driven pump to force air into an internal combustion engine in 1885; the turbocharger was invented by Swiss engineer Alfred Büchi, the head of diesel engine research at Gebrüder Sulzer, engine manufacturing company in Winterthur, who received a patent in 1905 for using a compressor driven by exhaust gases to force air into an internal combustion engine to increase power output, but it took another 20 years for the idea to come to fruition. The first use of turbocharging technology based on his design was for large marine engines, when the German Ministry of Transport commissioned the construction of the "Preussen" and "Hansestadt Danzig" passenger liners in 1923. Both ships featured twin ten-cylinder diesel engines with output boosted from 1750 to 2500 horsepower by turbochargers designed by Büchi and built under his supervision by Brown Boveri.
During World War I French engineer Auguste Rateau fitted turbochargers to Renault engines powering various French fighters with some success. In 1918, General Electric engineer Sanford Alexander Moss attached a turbocharger to a V12 Liberty aircraft engine; the engine was tested at Pikes Peak in Colorado at 14,000 ft to demonstrate that it could eliminate the power loss experienced in internal combustion engines as a result of reduced air pressure and density at high altitude. Turbochargers were first used in production aircraft engines such as the Napier Lioness in the 1920s, although they were less common than engine-driven centrifugal superchargers. Ships and locomotives equipped with turbocharged diesel engines began appearing in the 1920s. Turbochargers were used in aviation, most used by the United States. During World War II, notable examples of U. S. aircraft with turbochargers—which included mass-produced ones designed by General Electric for American aviation use—include the B-17 Flying Fortress, B-24 Liberator, P-38 Lightning, P-47 Thunderbolt.
The technology was used in experimental fittings by a number of other manufacturers, notably a variety of experimental inline engine-powered Focke-Wulf Fw 190 prototype models, with some developments for their design coming from the DVL, a predecessor of today's DLR agency, but the need for advanced high-temperature metals in the turbine, that were not available for production purposes during wartime, kept them out of widespread use. Turbochargers are used in car and commercial vehicles because they allow smaller-capacity engines to have improved fuel economy, reduced emissions, higher power and higher torque. In contrast to turbochargers, superchargers are mechanically driven by the engine. Belts, chains and gears are common methods of powering a supercharger, placing a mechanical load on the engine. For example, on the single-stage single-speed supercharged Rolls-Royce Merlin engine, the supercharger uses about 150 horsepower, yet the benefits outweigh the costs. This is. Another disadvantage of some superchargers is lower adiabatic efficiency when compared with turbochargers.
Adiabatic efficiency is a measure of a compressor's ability to compress air without adding excess heat to that air. Under ideal conditions, the compression process always results in elevated output temperature. Roots superchargers impart more heat to the air than turbochargers. Thus, for a given volume and pressure of air, the turbocharged air is cooler, as a result denser, containing more oxygen molecules, therefore more potential power than the supercharged air. In practical application the disparity between the two can be dramatic, with turbochargers producing 15% to 30% more power based on the differences in adiabatic efficiency. By comparison, a turbocharger does not place a direct mechanical load on the engine, although turbochargers place exhaust back pressure on engines, increasing pumping losses; this is more ef
A seismometer is an instrument that responds to ground motions, such as caused by earthquakes, volcanic eruptions, explosions. Seismometers are combined with a timing device and a recording device to form a seismograph; the output of such a device — recorded on paper or film, now recorded and processed digitally — is a seismogram. Such data is used to locate and characterize earthquakes, to study the earth's internal structure. A simple seismometer, sensitive to up-down motions of the Earth, is like a weight hanging from a spring, both suspended from a frame that moves along with any motion detected; the relative motion between the weight and the frame provides a measurement of the vertical ground motion. A rotating drum is attached to the frame and a pen is attached to the weight, thus recording any ground motion in a seismogram. Any movement of the ground moves the frame; the mass tends not to move because of its inertia, by measuring the movement between the frame and the mass, the motion of the ground can be determined.
Early seismometers used optical levers or mechanical linkages to amplify the small motions involved, recording on soot-covered paper or photographic paper. Modern instruments use electronics. In some systems, the mass is held nearly motionless relative to the frame by an electronic negative feedback loop; the motion of the mass relative to the frame is measured, the feedback loop applies a magnetic or electrostatic force to keep the mass nearly motionless. The voltage needed to produce this force is the output of the seismometer, recorded digitally. In other systems the weight is allowed to move, its motion produces an electrical charge in a coil attached to the mass which voltage moves through the magnetic field of a magnet attached to the frame; this design is used in a geophone, used in exploration for oil and gas. Seismic observatories have instruments measuring three axes: north-south, east-west, vertical. If only one axis is measured, it is the vertical because it is less noisy and gives better records of some seismic waves.
The foundation of a seismic station is critical. A professional station is sometimes mounted on bedrock; the best mountings may be in deep boreholes, which avoid thermal effects, ground noise and tilting from weather and tides. Other instruments are mounted in insulated enclosures on small buried piers of unreinforced concrete. Reinforcing rods and aggregates would distort the pier as the temperature changes. A site is always surveyed for ground noise with a temporary installation before pouring the pier and laying conduit. European seismographs were placed in a particular area after a destructive earthquake. Today, they are concentrated in high-risk regions; the word derives from the Greek σεισμός, seismós, a shaking or quake, from the verb σείω, seíō, to shake. Seismograph is another Greek term from γράφω, gráphō, to draw, it is used to mean seismometer, though it is more applicable to the older instruments in which the measuring and recording of ground motion were combined, than to modern systems, in which these functions are separated.
Both types provide a continuous record of ground motion. The technical discipline concerning such devices is called seismometry, a branch of seismology; the concept of measuring the "shaking" of something means that the word "seismograph" might be used in a more general sense. For example, a monitoring station that tracks changes in electromagnetic noise affecting amateur radio waves presents an rf seismograph, and Helioseismology studies the "quakes" on the Sun. The first seismometer was made in China during the 2nd Century; the first Western description of the device comes from the French physicist and priest Jean de Hautefeuille in 1703. The modern seismometer was developed in the 19th century. In December 2018, a seismometer was deployed on the planet Mars by the InSight lander, the first time a seismometer was placed onto the surface of another planet. In AD 132, Zhang Heng of China's Han dynasty invented the first seismoscope, called Houfeng Didong Yi; the description we have, from the History of the Later Han Dynasty, says that it was a large bronze vessel, about 2 meters in diameter.
When there was an earthquake, one of the dragons' mouths would open and drop its ball into a bronze toad at the base, making a sound and showing the direction of the earthquake. On at least one occasion at the time of a large earthquake in Gansu in AD 143, the seismoscope indicated an earthquake though one was not felt; the available text says that inside the vessel was a central column that could move along eight tracks. The first earthquake recorded by this seismoscope was "somewhere in the east". Days a rider from the east reported this earthquake. By the 13th century, seismographic devices existed in the Maragheh observatory in Persia. French physicist and priest Jean de Hautefeuille built one in 1703. After 1880, most seismometers were descend
Hall effect sensor
A Hall effect sensor is a device, used to measure the magnitude of a magnetic field. Its output voltage is directly proportional to the magnetic field strength through it. Hall effect sensors are used for proximity sensing, speed detection, current sensing applications. A Hall sensor is combined with threshold detection so that it acts as and is called a switch. Seen in industrial applications such as the pictured pneumatic cylinder, they are used in consumer equipment, they can be used in computer keyboards, an application that requires ultra-high reliability. Hall sensors are used to time the speed of wheels and shafts, such as for internal combustion engine ignition timing and anti-lock braking systems, they are used in brushless DC electric motors to detect the position of the permanent magnet. In the pictured wheel with two spaced magnets, the voltage from the sensor will peak twice for each revolution; this arrangement is used to regulate the speed of disk drives. A Hall probe contains an indium compound semiconductor crystal such as indium antimonide, mounted on an aluminum backing plate, encapsulated in the probe head.
The plane of the crystal is perpendicular to the probe handle. Connecting leads from the crystal is brought down through the handle to the circuit box; when the Hall probe is held so that the magnetic field lines are passing at right angles through the sensor of the probe, the meter gives a reading of the value of magnetic flux density. A current is passed through the crystal which, when placed in a magnetic field has a "Hall effect" voltage developed across it; the Hall effect is seen. The natural electron drift of the charge carriers causes the magnetic field to apply a Lorentz force to these charge carriers; the result is what is seen as charge separation, with a buildup of either positive or negative charges on the bottom or on the top of the plate. The crystal measures 5 mm square; the probe handle, being made of a non-ferrous material, has no disturbing effect on the field. A Hall probe should be calibrated against a known value of magnetic field strength. For a solenoid the Hall probe is placed in the center.
In a Hall effect sensor, a thin strip of metal has a current applied along it. In the presence of a magnetic field, the electrons in the metal strip are deflected toward one edge, producing a voltage gradient across the short side of the strip. Hall effect sensors have an advantage over inductive sensors in that, while inductive sensors respond to a changing magnetic field which induces current in a coil of wire and produces voltage at its output, Hall effect sensors can detect static magnetic fields. In its simplest form, the sensor operates as an analog transducer, directly returning a voltage. With a known magnetic field, its distance from the Hall plate can be determined. Using groups of sensors, the relative position of the magnet can be deduced; when a beam of charged particles passes through a magnetic field, forces act on the particles and the beam is deflected from a straight path. The flow of electrons through a conductor form a beam of charged carriers; when an conductor is placed in a magnetic field perpendicular to the direction of the electrons, they will be deflected from a straight path.
As a consequence, one plane of the conductor will become negatively charged and the opposite side will become positively charged. The voltage between these planes is called the Hall voltage; when the force on the charged particles from the electric field balances the force produced by magnetic field, the separation of them will stop. If the current is not changing the Hall voltage is a measure of the magnetic flux density. There are two kinds of Hall effect sensors. One is linear; the key factor determining sensitivity of Hall effect sensors is high electron mobility. As a result, the following materials are suitable for Hall effect sensors: gallium arsenide indium arsenide indium phosphide indium antimonide graphene Hall effect sensors are linear transducers; as a result, such sensors require a linear circuit for processing of the sensor's output signal. Such a linear circuit: provides a constant driving current to the sensors amplifies the output signalIn some cases the linear circuit may cancel the offset voltage of Hall effect sensors.
Moreover, AC modulation of the driving current may reduce the influence of this offset voltage. Hall effect sensors with linear transducers are integrated with digital electronics; this enables advanced corrections to the sensor's characteristics and digital interfacing to microprocessor systems. In some solutions of IC Hall effect sensors a DSP is used, which provides for more choices among processing techniques; the Hall effect sensor interfaces may include input diagnostics, fault protection for transient conditions, short/open circuit detection. It may provide and monitor the current to the Hall effect sensor itself. There are precision IC products available to handle these features. A Hall effect sensor may operate as an electronic switch; such a switch is much more reliable. It can be operated at higher frequencies than a mechanical switch, it does not suffer from contact bounce because a solid state
Mass flow sensor
A mass flow sensor is a sensor used to determine the mass flow rate of air entering a fuel-injected internal combustion engine. The air mass information is necessary for the engine control unit to balance and deliver the correct fuel mass to the engine. Air changes its density with pressure. In automotive applications, air density varies with the ambient temperature and the use of forced induction, which means that mass flow sensors are more appropriate than volumetric flow sensors for determining the quantity of intake air in each cylinder. There are two common types of mass airflow sensors in use on automotive engines; these are the hot wire. Neither design employs technology. However, with additional sensors and inputs, an engine's ECU can determine the mass flow rate of intake air. Both approaches are used exclusively on electronic fuel injection engines. Both sensor designs output a 0.0–5.0 volt or a pulse-width modulation signal, proportional to the air mass flow rate, both sensors have an intake air temperature sensor incorporated into their housings for most post on-board diagnostics vehicles.
Vehicles prior to 1996 could have MAF without an IAT. An example is 1994 Infiniti Q45; when a MAF sensor is used in conjunction with an oxygen sensor, the engine's air/fuel ratio can be controlled accurately. The MAF sensor provides the open-loop controller predicted air flow information to the ECU, the oxygen sensor provides closed-loop feedback in order to make minor corrections to the predicted air mass. See manifold absolute pressure sensor; the VAF sensor measures the air flow into the engine with a spring-loaded air vane attached to a variable resistor. The vane moves in proportion to the airflow. A voltage is applied to the potentiometer and a proportional voltage appears on the output terminal of the potentiometer in proportion to the angle the vane rotates, or the movement of the vane may directly regulate the amount of fuel injected, as in the K-Jetronic system. Many VAF sensors have an air-fuel adjustment screw, which opens or closes a small air passage on the side of the VAF sensor.
This screw controls the air-fuel mixture by letting a metered amount of air flow past the air flap, thereby leaning or richening the mixture. By turning the screw clockwise the mixture is counterclockwise the mixture is leaned; the vane moves because of the drag force of the air flow against it. The drag force depends on air velocity and the shape of the vane, see drag equation; some VAF sensors include an additional intake air temperature sensor to allow the engines ECU to calculate the density of the air, the fuel delivery accordingly. The vane meter approach has some drawbacks: it restricts airflow which limits engine output its moving electrical or mechanical contacts can wear finding a suitable mounting location within a confined engine compartment is problematic the vane has to be oriented with respect to gravity. In some manufacturers fuel pump control was part on the VAF internal wiring. A hot wire mass airflow sensor determines the mass of air flowing into the engine’s air intake system.
The theory of operation of the hot wire mass airflow sensor is similar to that of the hot wire anemometer. This is achieved by heating a wire suspended in the engine’s air stream, like a toaster wire, with either a constant voltage over the wire or a constant current through the wire; the wire's electrical resistance increases as the wire’s temperature increases, which varies the electrical current flowing through the circuit, according to Ohm's law. When air flows past the wire, the wire cools, decreasing its resistance, which in turn allows more current to flow through the circuit, since the supply voltage is a constant; as more current flows, the wire’s temperature increases until the resistance reaches equilibrium again. The current increase or decrease is proportional to the mass of air flowing past the wire; the integrated electronic circuit converts the proportional measurement into a calibrated signal, sent to the ECU. If air density increases due to pressure increase or temperature drop, but the air volume remains constant, the denser air will remove more heat from the wire indicating a higher mass airflow.
Unlike the vane meter's paddle sensing element, the hot wire responds directly to air density. This sensor's capabilities are well suited to support the gasoline combustion process which fundamentally responds to air mass, not air volume; this sensor sometimes employs a mixture screw, but this screw is electronic and uses a variable resistor instead of an air bypass screw. The screw needs more turns to achieve the desired results. A hot wire burn-off cleaning circuit is employed on some of these sensors. A burn-off relay applies a high current through the platinum hot wire after the vehicle is turned off for a second or so, thereby burning or vaporizing any contaminants that have stuck to the platinum hot wire element; the hot film MAF sensor works somewhat similar to the hot wire MAF sensor, but instead it outputs a frequency signal. This sensor uses a hot film-grid instead of a hot wire, it is found in late 80’s early 90’s fuel-injected vehicles. The output frequency is directly proportional to the air mass entering the engine.
So as mass flow increases so does frequency. These sensors tend to cause intermittent problems due to internal electrical failures; the use of an oscilloscope is recommended to check the outp
A radar speed gun is a device used to measure the speed of moving objects. It is used in law-enforcement to measure the speed of moving vehicles and is used in professional spectator sport, for things such as the measurement of bowling speeds in cricket, speed of pitched baseballs and tennis serves. A radar speed gun is a Doppler radar unit that may be vehicle-mounted or static, it measures the speed of the objects at which it is pointed by detecting a change in frequency of the returned radar signal caused by the Doppler effect, whereby the frequency of the returned signal is increased in proportion to the object's speed of approach if the object is approaching, lowered if the object is receding. Such devices are used for speed limit enforcement, although more modern LIDAR speed gun instruments, which use pulsed laser light instead of radar, began to replace radar guns during the first decade of the twenty-first century, because of limitations associated with small radar systems; the radar speed gun was invented by John L. Barker Sr. and Ben Midlock, who developed radar for the military while working for the Automatic Signal Company in Norwalk, CT during World War II.
Automatic Signal was approached by Grumman Aircraft Corporation to solve the specific problem of terrestrial landing gear damage on the now-legendary PBY Catalina amphibious aircraft. Barker and Midlock cobbled a Doppler radar unit from coffee cans soldered shut to make microwave resonators; the unit was installed at the end of the runway, aimed directly upward to measure the sink rate of landing PBYs. After the war and Midlock tested radar on the Merritt Parkway. In 1947, the system was tested by the Connecticut State Police in Glastonbury, Connecticut for traffic surveys and issuing warnings to drivers for excessive speed. Starting in February 1949, the state police began to issue speeding tickets based on the speed recorded by the radar device. In 1948, radar was used in Garden City, New York. Speed guns use Doppler radar to perform speed measurements. Radar speed guns, like other types of radar, consist of receiver, they send out a radio signal in a narrow beam receive the same signal back after it bounces off the target object.
Due to a phenomenon called the Doppler effect, if the object is moving toward or away from the gun, the frequency of the reflected radio waves when they come back is different from the transmitted waves. When the object is approaching the radar, the frequency of the return waves is higher than the transmitted waves. From that difference, the radar speed gun can calculate the speed of the object from which the waves have been bounced; this speed is given by the following equation: v = Δ f f c 2 where c is the speed of light, f is the emitted frequency of the radio waves and Δf is the difference in frequency between the radio waves that are emitted and those received back by the gun. This equation holds only when object speeds are low compared to that of light, but in everyday situations, this is the case and the velocity of an object is directly proportional to this difference in frequency. After the returning waves are received, a signal with a frequency equal to this difference is created by mixing the received radio signal with a little of the transmitted signal.
Just as two different musical notes played together create a beat note at the difference in frequency between them, so when these two radio signals are mixed they create a "beat" signal. An electrical circuit measures this frequency using a digital counter to count the number of cycles in a fixed time period, displays the number on a digital display as the object's speed. Since this type of speed gun measures the difference in speed between a target and the gun itself, the gun must be stationary in order to give a correct reading. If a measurement is made from a moving car, it will give the difference in speed between the two vehicles, not the speed of the target relative to the road, so a different system has been designed to work from moving vehicles. In so-called "moving radar", the radar antenna receives reflected signals from both the target vehicle and stationary background objects such as the road surface, nearby road signs, guard rails and streetlight poles. Instead of comparing the frequency of the signal reflected from the target with the transmitted signal, it compares the target signal with this background signal.
The frequency difference between these two signals gives the true speed of the target vehicle. Modern radar speed guns operate at X, K, Ka, Ku bands. Radar guns that operate using the X band frequency range are becoming less common because they produce a strong and detectable beam. Most automatic doors utilize radio waves in the X band range and can affect the readings of police radar; as a result, K band and Ka band are most used by police agencies. Some motorists install radar detectors which can alert them to the presence of a speed trap ahead, the microwave signals from radar may change the quality of reception of AM and FM radio signals when tuned to a weak station. For these reasons, hand-held radar includes an on-off trigger and the radar is only turned on when the operator is about to make a measurement. Radar detectors are illegal in some areas. Traffic radar comes in many models. Hand-held units are b
Air–fuel ratio meter
An air–fuel ratio meter monitors the air–fuel ratio of an internal combustion engine. Called air–fuel ratio gauge, air–fuel meter, or air–fuel gauge, it reads the voltage output of an oxygen sensor, sometimes called AFR sensor or lambda sensor, whether it be from a narrow band or wide band oxygen sensor. The original narrow-band oxygen sensors became factory installed standard in the late 1970s and early 1980s. In recent years a newer and much more accurate wide-band sensor, though more expensive, has become available. Most stand-alone narrow-band meters have 10 LEDs and some have more. Common, narrow band meters in round housings with the standard mounting 2 1/16" and 2 5/8" diameters, as other types of car'gauges'; these have 10 or 20 LEDs. Analogue'needle' style gauges are available; as stated above, there are wide-band meters that are mounted in housings. Nearly all of these show the air–fuel ratio on a numeric display since the wide-band sensors provide a much more accurate reading; as wide-band sensors use more accurate electronics, these meters are more expensive.
Determining the condition of the oxygen sensor: A malfunctioning oxygen sensor will result in air–fuel ratios that respond more to changing engine conditions. A damaged or defective sensor may lead to increased fuel consumption and increased pollutant emissions as well as decreased power and throttle response. Most engine management systems will detect a defective oxygen sensor. Reducing emissions: Keeping the air–fuel mixture near the stoichiometric ratio of 14.7:1 allows the catalytic converter to operate at maximum efficiency. Fuel economy: An air–fuel mixture leaner than the stoichiometric ratio will result in near-optimal fuel mileage, costing less per distance traveled and producing the least amount of CO2 emissions. However, from the factory, cars are designed to operate at the stoichiometric ratio to maximize the efficiency and life of the catalytic converter. While it may be possible to run smoothly at mixtures leaner than the stoichiometric ratio, manufacturers must focus on emissions and catalytic converter life as a higher priority due to U.
S. EPA regulations. Engine performance: Carefully mapping out air–fuel ratios throughout the range of rpm and manifold pressure will maximize power output in addition to reducing the risk of detonation. Lean mixtures improve the fuel economy but cause sharp rises in the amount of nitrogen oxides. If the mixture becomes too lean, the engine may fail to ignite, causing misfire and a large increase in unburned hydrocarbon emissions. Lean mixtures burn hotter and may cause rough idle, hard starting and stalling, can damage the catalytic converter, or burn valves in the engine; the risk of spark knock/engine knocking is increased when the engine is under load. Mixtures that are richer than stoichiometric allow for greater peak engine power when using vaporized liquid fuel due to the mixture not being able to reach a homogenized state so extra fuel is added to ensure all oxygen is burned producing maximum power; the ideal mixture in this type of operation depends on the individual engine. For example, engines with forced induction such as turbochargers and superchargers require a richer mixture under wide open throttle than aspirated engines.
Forced induction engines can be catastrophically damaged by burning too lean for too long. The leaner the air–fuel mixture, the higher the combustion temperature is inside the cylinder. Too high a temperature will destroy an engine – melting the pistons and valves; this can happen if one ports the head and/or manifolds or increase boost without compensating by installing larger or more injectors, and/or increasing the fuel pressure to a sufficient level. Conversely, engine performance can be lessened by increasing fueling without increasing air flow into the engine. Furthermore, if an engine is leaned to the point where its exhaust gas temperature starts to fall, its cylinder head temperature will fall; this is only recommended in the cruising configuration, never when accelerating hard, but is becoming popular in aviation circles, where the appropriate engine monitoring gauges are fitted and the fuel air mixture can be manually adjusted. Cold engines typically require more fuel and a richer mixture when first started, because fuel does not vaporize as well when cold and therefore requires more fuel to properly "saturate" the air.
Rich mixtures burn slower and decrease the risk of spark knock/engine knocking when the engine is under load. However, rich mixtures increase carbon monoxide emissions; the early introduction of the oxygen sensor came about in the late 1970s. Since zirconia has been the material of choice for its construction; the zirconia O2 sensor produces its own voltage. The varying voltage will display on a scope as a waveform somewhat resembling a sine wave when in closed loop control; the actual voltage, generated is a measure of the oxygen, needed to complete the combustion of the CO and HC present at the sensor tip. The stoichiometric air-fuel ratio mixture ratio for gasoline engine is the theoretical air-fuel ratio at which all of the fuel will react with all of the available oxygen resulting in complete combustion. At or near this ratio, the combustion process produces the best balance between power and low emissions. At the stoichiometric air-fuel ratio, the generated O2 sensor voltage is about 450 mV.
The Engine Control Module recognizes a rich condition above the 450 mV level, a lean condi