Ram-air intake

A ram-air intake is any intake design which uses the dynamic air pressure created by vehicle motion to increase the static air pressure inside of the intake manifold on an internal combustion engine, thus allowing a greater massflow through the engine and hence increasing engine power. Design features Ram air intakes on a 1973 Mustang Mach 1 Motorcycle with gooseneck mounted hypercharger air intake The ram-air intake works by reducing the intake air velocity by increasing the cross-sectional area of the intake ducting. When gas velocity goes down the dynamic pressure is reduced, while the static pressure is increased. The increased static pressure in the plenum chamber has a positive effect on engine power, both because of the pressure itself and the increased air density that this higher pressure gives. Ram-air systems are used on high-performance vehicles, most often on motorcycles and performance cars. The 1990 Kawasaki Ninja ZX-11 C1 model used a ram-air intake, the very first on any production motorcycle.Ram-air was a feature on some cars in the sixties, falling out of favor in the seventies, but recently making a comeback. While ram-air may increase the volumetric efficiency of an engine, they can be difficult to combine with carburetors, which rely on a venturi-engineered pressure drop to draw fuel through the main jet. As the pressurised ram-air may kill this venturi effect, the carburetor will need to be designed to take this into account; or the engine may need fuel-injection. Modern parachutes and kites use a ram-air system to pressurize a series of cells to provide the aerofoil shape. At low speeds (subsonic speeds) increases in static pressure are however limited to a few percent. Given that the air velocity is reduced to zero without losses the pressure increase can be calculated accordingly. The lack of losses also means without heating the air. Thus a ram-air intake also is a cold air intake. In some cars the intake is placed behind the radiator, where not only the air is hot, but the pressure is below ambient pressure. The ram-air intake effect may be small, but so are other mild tuning techniques to increase cylinder filling like using larger, fresh air filters, high flow mass flow sensors, velocity stacks, tuned air box and large tubes from the filter to the engine. References Cabello, Cabello; Baz, Pablo (2015-06-13). "Sistema aerodinámico Ram-Air: funcionamiento" . Motociclismo (in Spanish). Retrieved 2016-08-20. Burns, John (December 24, 2013). "30 Years of Ninjas: 1984 GPz900 Ninja to 1990 ZX-11!". Cycle World. Retrieved December 2, 2016. "Ram Air: Test". Sport Rider. October 1999. Retrieved December 2, 2016.

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Manifold vacuum

Manifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere. Manifold vacuum is an effect of a piston's movement on the induction stroke and the choked flow through a throttle in the intake manifold of an engine. It is a measure of the amount of restriction of airflow through the engine, and hence of the unused power capacity in the engine. In some engines, the manifold vacuum is also used as an auxiliary power source to drive engine accessories and for the crankcase ventilation system. Manifold vacuum should not be confused with venturi vacuum, which is an effect exploited in carburetors to establish a pressure difference roughly proportional to mass airflow and to maintain a somewhat constant air/fuel ratio. It is also used in light airplanes to provide airflow for pneumatic gyroscopic instruments. Overview The rate of airflow through an internal combustion engine is an important factor determining the amount of power the engine generates. Most gasoline engines are controlled by limiting that flow with a throttle that restricts intake airflow, while a diesel engine is controlled by the amount of fuel supplied to the cylinder, and so has no "throttle" as such. Manifold vacuum is present in all naturally aspirated engines that use throttles (including carbureted and fuel injected gasoline engines using the Otto cycle or the two-strokecycle; diesel engines do not have throttle plates). The mass flow through the engine is the product of the rotation rate of the engine, the displacement of the engine, and the density of the intake stream in the intake manifold. In most applications the rotation rate is set by the application (engine speed in a vehicle or machinery speed in other applications). The displacement is dependent on the engine geometry, which is generally not adjustable while the engine is in use (although a handful of models do have this feature, see variable displacement). Restricting the input flow reduces the density (and hence pressure) in the intake manifold, reducing the amount of power produced. It is also a major source of engine drag (see engine braking), as the engine must pump material from the low-pressure intake manifold into the exhaust manifold (at ambient atmospheric pressure). When the throttle is opened (in a car, the accelerator pedal is depressed), ambient air is free to fill the intake manifold, increasing the pressure (filling the vacuum). A carburetoror fuel injection system adds fuel to the airflow in the correct proportion, providing energy to the engine. When the throttle is opened all the way, the engine's air induction system is exposed to full atmospheric pressure, and maximum airflow through the engine is achieved. In a naturally aspirated engine, output power is limited by...

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Naturally aspirated engine

A naturally aspirated engine is an internal combustion engine in which oxygen intake depends solely on atmospheric pressure and does not rely on forced induction through a turbocharger or a supercharger. Many sports cars specifically use naturally aspirated engines to avoid turbo lag. Description In a naturally aspirated engine, air for combustion (diesel cycle in a diesel engine or specific types of Otto cycle in petrol engines—namely petrol direct injection), or an air/fuel mixture (traditional Otto cycle petrol engines)—is drawn into the engine’s cylinders by atmospheric pressure acting against a partial vacuum that occurs as the piston travels downwards toward bottom dead centre during the intake stroke. Owing to innate restriction in the engine's inlet tract, which includes the intake manifold, a small pressure drop occurs as air is drawn in, resulting in a volumetric efficiency of less than 100 percent—and a less than complete air charge in the cylinder. The density of the air charge, and therefore the engine's maximum theoretical power output, in addition to being influenced by induction system restriction, is also affected by engine speed and atmospheric pressure, the latter of which decreases as the operating altitude increases. This is in contrast to a forced-induction engine, in which a mechanically driven supercharger or an exhaust-driven turbocharger is employed to facilitate increasing the mass of intake air beyond what could be produced by atmospheric pressure alone. Nitrous oxide can also be used to artificially increase the mass of oxygen present in the intake air. This is accomplished by injecting liquid nitrous oxide into the intake, which supplies significantly more oxygen in a given volume than is possible with atmospheric air. Nitrous oxide is 36.352% oxygen by mass as compared with atmospheric air at 20.95%. Nitrous oxide also boils at −127.3 °F (−88.5 °C) at atmospheric pressures and offers significant cooling from the latent heat of vaporization, which also aids in increasing the overall air charge density significantly compared to natural aspiration. As a two-stroke diesel engine is incapable of this natural aspiration, some method of charging the cylinders with scavenging air must be integrated into the engine design. This is usually achieved with a positive displacement blower driven by the crankshaft. The blower does not act as a supercharger in this application, as it is sized to produce a volume of air flow that is in direct proportion to engine's requirement for combustion, at a given power and speed. By the Society of Automotive Engineer's definition, a mechanically scavenged two-stroke diesel engine is considered to be naturally aspirated. Applications Most automobile petrol engines, as well as many small engines used for non-automotive purposes, are naturally aspirated. Most modern diesel engines powering highway vehicles are turbocharged to produce a more favourable power-to-weight ratio, a higher torque curve, as well as better fuel efficiency and...

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Air filter

A particulate air filter is a device composed of fibrous or porous materials which removes solid particulates such as dust, pollen, mold, and bacteria from the air. Filters containing an absorbent or catalyst such as charcoal (carbon) may also remove odors and gaseous pollutants such as volatile organic compounds or ozone. Air filters are used in applications where air quality is important, notably in building ventilation systems and in engines. Some buildings, as well as aircraft and other human-made environments (e.g., satellites and space shuttles) use foam, pleated paper, or spun fiberglass filter elements. Another method, air ionizers, use fibers or elements with a static electric charge, which attract dust particles. The air intakes of internal combustion engines and air compressors tend to use either paper, foam, or cotton filters. Oil bath filters have fallen out of favor. The technology of air intake filters of gas turbines has improved significantly in recent years, due to improvements in the aerodynamics and fluid dynamics of the air-compressor part of the gas turbines. HEPA filters HEPA filters (high-efficiency particulate air filters) remove at least 99.97% of particles that are 3 micormeters in diameter, and efficiently remove both larger and smaller particles. Automotive cabin air filters The cabin air filter is typically a pleated-paper filter that is placed in the outside-air intake for the vehicle's passenger compartment. Some of these filters are rectangular and similar in shape to the combustion air filter. Others are uniquely shaped to fit the available space of particular vehicles' outside-air intakes. The first automaker to include a disposable filter to clean the ventilation system was the Nash Motors "Weather Eye", introduced in 1940. Being a relatively recent addition to automobile equipment, this filter is often overlooked. Clogged or dirty cabin air filters can significantly reduce airflow from the cabin vents, as well as introduce allergens into the cabin air stream, and since the cabin air temperature depends upon the flow rate of the air passing through the heater core, the evaporator or both, they can greatly reduce the effectiveness of the vehicle's air conditioning and the heating performance. It is suggested that car air filters be changed every 12,000 – 15,000 miles, while others say 15,000 – 30,000 depending on the manufacturer's instructions or the car's manual. The poor performance of these filters is obscured by manufacturers by not using the minimum efficiency reporting value (MERV) rating system. Some people mistakenly believe that some of these are HEPA filters. Internal combustion engine air filters Used auto engine air filter, clean side Used auto engine air filter, dirty side Auto engine air filter clogged with dust and grime Low-temperature oxidation catalyst used to convert carbon monoxide to less toxic carbon dioxide at room temperature. It can also remove formaldehyde from the air. The combustion air filter prevents abrasive particulate matter from entering the engine's cylinders, where it would cause mechanical wear and oil contamination. Most fuel injected vehicles use a pleated paper filter...

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Diesel particulate filter

A diesel particulate filter (DPF) is a device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine. A diesel particulate filter (top left) in a Peugeot Off-road - DPF Installation Mode of action Wall-flow diesel particulate filters usually remove 85% or more of the soot, and under certain conditions can attain soot removal efficiencies approaching 100%. Some filters are single-use, intended for disposal and replacement once full of accumulated ash. Others are designed to burn off the accumulated particulate either passively through the use of a catalyst or by active means such as a fuel burner which heats the filter to soot combustion temperatures. This is accomplished by engine programming to run (when the filter is full) in a manner that elevates exhaust temperature, in conjunction with an extra fuel injector in the exhaust stream that injects fuel to react with a catalyst element to burn off accumulated soot in the DPF filter, or through other methods. This is known as "filter regeneration". Cleaning is also required as part of periodic maintenance, and it must be done carefully to avoid damaging the filter. Failure of fuel injectors or turbochargers resulting in contamination of the filter with raw diesel or engine oil can also necessitate cleaning. The regeneration process occurs at road speeds higher than can generally be attained on city streets; vehicles driven exclusively at low speeds in urban traffic can require periodic trips at higher speeds to clean out the DPF. If the driver ignores the warning light and waits too long to operate the vehicle above 40 miles per hour (64 km/h), the DPF may not regenerate properly, and continued operation past that point may spoil the DPF completely so it must be replaced. Some newer diesel engines, namely those installed in combination vehicles, can also perform what is called a Parked Regeneration, where the engine increases RPM to around 1400 while parked, to increase the temperature of the exhaust. Diesel engines produce a variety of particles during combustion of the fuel/air mix due to incomplete combustion. The composition of the particles varies widely dependent upon engine type, age, and the emissions specification that the engine was designed to meet. Two-stroke diesel engines produce more particulate per unit of power than do four-stroke diesel engines, as they burn the fuel-air mix less completely. Diesel particulate matter resulting from the incomplete combustion of diesel fuel produces soot (black carbon) particles. These particles include tiny nanoparticles—smaller than a thousandth of a millimeter (one micron). Soot and other particles from diesel engines worsen the particulate matter pollution in the air...

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Engine control unit

An engine control unit (ECU), also commonly called an engine control module (ECM), is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. It does this by reading values from a multitude of sensors within the engine bay, interpreting the data using multidimensional performance maps (called lookup tables), and adjusting the engine actuators accordingly. Before ECUs, air-fuel mixture, ignition timing, and idle speed were mechanically set and dynamically controlled by mechanical and pneumatic means. If the ECU has control over the fuel lines, then it is referred to as an Electronic Engine Management System (EEMS). The fuel injection system has the major role to control the engine's fuel supply. The whole mechanism of the EEMS is controlled by a stack of sensors and actuators. An ECU from a 1996 Chevrolet Beretta. Workings Control of air–fuel ratio Most modern engines use some type of fuel injection to deliver fuel to the cylinders. The ECU determines the amount of fuel to inject based on a number of sensor readings. Oxygen sensors tell the ECU whether the engine is running rich (too much fuel or too little oxygen) or running lean (too much oxygen or too little fuel) as compared to ideal conditions (known as stoichiometric). The throttle position sensors tell the ECU how far the throttle plate is opened when you press the accelerator. The mass air flow sensor measures the amount of air flowing into the engine through the throttle plate. The engine coolant temperature sensor measures whether the engine is warmed up or cool. If the engine is still cool, additional fuel will be injected. Air–fuel mixture control of carburetors with computers is designed with a similar principle, but a mixture control solenoid or stepper motor is incorporated in the float bowl of the carburetor. Control of idle speed Most engine systems have idle speed control built into the ECU. The engine RPM is monitored by the crankshaft position sensor which plays a primary role in the engine timing functions for fuel injection, spark events, and valve timing. Idle speed is controlled by a programmable throttle stop or an idle air bypass control stepper motor. Early carburetor-based systems used a programmable throttle stop using a bidirectional DC motor. Early throttle body injection (TBI) systems used an idle air control stepper motor. Effective idle speed control must anticipate the engine load at idle. A full authority throttle control system may be used to control idle speed, provide cruise control functions and top speed limitation. It also monitors the ECU section for reliability. Control of variable valve timing Some engines have Variable Valve...

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Engine tuning

Engine tuning is an adjustment, modification of the internal combustion engine, or modification to its control unit, otherwise known as its ECU (Engine Control Unit). It is adjusted to yield optimal performance, to increase an engine's power output, economy, or durability. These goals may be mutually exclusive, and an engine may be detuned with respect to output (work) in exchange for better economy or longer engine life due to lessened stress on engine components. Engine tuning has a lengthy history, almost as long as that of the development of the automobile, originating with the development of early racing cars and the post-war hot-rod movement. Tuning can describe a wide variety of adjustments and modifications, from the routine adjustment of the carburetor and ignition system to significant engine overhauls. At the other end of the scale, performance tuning of an engine can involve revisiting some of the design decisions taken at quite an early stage in the development of the engine. Setting the idle speed, fuel/air mixture, carburetor balance, spark plug and distributor point gaps, and ignition timing were regular maintenance items for all older engines and the final but essential steps in setting up a racing engine. On modern engines equipped with electronic ignition and fuel injection, some or all of these tasks are automated, although they still require periodic calibration.   Vintage engine testing equipment that can test ignition timing, ignition dwell, manifold vacuum and exhaust emissions Engine tune-up A tune-up usually refers to the routine servicing of the engine to meet the manufacturer's specifications. Tune-ups are needed periodically according to the manufacturer's recommendations to ensure that an automobile runs as expected. Relative to older automobiles, modern automobiles now typically require only a small number of tune-ups over the course of an approximate 250,000-kilometre (160,000 mi) or a 10-year lifespan. This can be attributed to improvements in the production process, with imperfections and errors reduced by computer automation, and also significant improvement in the quality of consumables, such as the availability of fully synthetic engine oil. Tune-ups may include the following: Adjustment of the carburetor idle speed and the air-fuel mixture Inspection and possible replacement of ignition system components like spark plugs, contact breaker points, distributor cap and distributor rotor Replacement of the air filter and other filters Inspection of emission controls Valvetrain adjustment In early days, mechanics finishing the tune-up of a performance car such as a Ferrari would take it around a track several times to burn out any built-up carbon; this is known as an Italian tuneup. Chip tuning Modern engines are equipped with an engine management system (EMS)/Engine Control Unit (ECU) which can be modified to different settings, producing different...

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