Active Valve Control System
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Active Valve Control System
The active valve control system (AVCS) is an automobile variable valve timing technology used by Subaru. It varies the timing of the valves by using hydraulic oil pressure to rotate the camshaft, known as "phasing", in order to provide optimal valve timing for engine load conditions. The system is closed loop using the camshaft sensors, crankshaft sensors, air flow meter, throttle position as well as oxygen sensors and/or Air-Fuel ratio sensors in order to calculate engine load. The ECU is programmed to operate control valves that adjust the delivery of the hydraulic pressure in order to move the camshaft into the position that will provide the engine with the best performance while meeting emissions standards. AVCS is used on the Version 7 and up EJ207 engines, the EJ204, EJ254, EJ255, EJ257, the second generation EZ30D (2005+ in the USA market) found in the Legacy Outback, Legacy 2.0R, 3.0R and the B9 Tribeca. A dual AVCS system phases both the intake and exhaust camshafts on t ...
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Variable Valve Timing
In internal combustion engines, variable valve timing (VVT) is the process of altering the timing of a valve lift event, and is often used to improve performance, fuel economy or emissions. It is increasingly being used in combination with variable valve lift systems. There are many ways in which this can be achieved, ranging from mechanical devices to electro-hydraulic and camless systems. Increasingly strict emissions regulations are causing many automotive manufacturers to use VVT systems. Two-stroke engines use a power valve system to get similar results to VVT. Background theory The valves within an internal combustion engine are used to control the flow of the intake and exhaust gases into and out of the combustion chamber. The timing, duration and lift of these valve events has a significant impact on engine performance. Without variable valve timing or variable valve lift, the valve timing is the same for all engine speeds and conditions, therefore compromises are neces ...
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Subaru
( or ; ) is the automaker, automobile manufacturing division of Japanese transportation conglomerate (company), conglomerate Subaru Corporation (formerly known as Fuji Heavy Industries), the Automotive industry#By manufacturer, twenty-first largest automaker by production worldwide in 2017. Subaru cars are known for their use of a flat engine, boxer engine layout in most vehicles above 1,500 cc. The Symmetrical All Wheel Drive drive-train layout was introduced in 1972. Both became standard equipment for mid-size and smaller cars in most markets by 1996. The lone exception is the Subaru BRZ, BRZ, introduced in 2012 via a partnership with Toyota, which pairs the boxer engine with rear-wheel-drive. Subaru also offers turbocharged versions of their passenger cars, such as the Subaru WRX, WRX, Subaru Legacy, Legacy and Subaru Outback, Outback XT, Subaru Ascent, Ascent, and formerly the Subaru Legacy, Legacy GT and Subaru Forester, Forester XT. In Western markets, Subaru vehi ...
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Hydraulic
Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counterpart of pneumatics, which concerns gases. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the applied engineering using the properties of fluids. In its fluid power applications, hydraulics is used for the generation, control, and transmission of power by the use of pressurized liquids. Hydraulic topics range through some parts of science and most of engineering modules, and cover concepts such as pipe flow, dam design, fluidics and fluid control circuitry. The principles of hydraulics are in use naturally in the human body within the vascular system and erectile tissue. Free surface hydraulics is the branch of hydraulics dealing with free surface flow, such as occurring in rivers, canals, lakes, estuar ...
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Motor Oil
Motor oil, engine oil, or engine lubricant is any one of various substances used for the lubrication of internal combustion engines. They typically consist of base oils enhanced with various additives, particularly antiwear additives, detergents, dispersants, and, for multi-grade oils, viscosity index improvers. The main function of motor oil is to reduce friction and wear on moving parts and to clean the engine from sludge (one of the functions of dispersants) and varnish (detergents). It also neutralizes acids that originate from fuel and from oxidation of the lubricant (detergents), improves sealing of piston rings, and cools the engine by carrying heat away from moving parts. In addition to the aforementioned basic constituents, almost all lubricating oils contain corrosion and oxidation inhibitors. Motor oil may be composed of only a lubricant base stock in the case of non- detergent oil, or a lubricant base stock plus additives to improve the oil's detergency, extreme p ...
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Camshaft
A camshaft is a shaft that contains a row of pointed cams, in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition systems and early electric motor speed controllers. Camshafts in piston engines are usually made from steel or cast iron, and the shape of the cams greatly affects the engine's characteristics. History Trip hammers are one of the early uses of a form of cam to convert rotating motion, e.g. from a waterwheel, into the reciprocating motion of a hammer used in forging or to pound grain. Evidence for these exists back to the Han Dynasty in China, and they were widespread by the medieval period. The camshaft was described in 1206 by engineer Al-Jazari. He employed it as part of his automata, water-raising machines, and water clocks such as the castle clock. Once the rotative version of the steam engine was developed in the late 18th century, the ...
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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. 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 of controlling the engine's fuel supply. The whole mechanism of the EEMS is controlled by a stack of sensors and actuators. Workings Control of air–fuel ratio Most modern engines use some type of fuel injection to deliver fuel to the cylinders. ...
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Subaru Legacy
The is a mid-size car built by Japanese automobile manufacturer Subaru since 1989. The maker's flagship car, it is unique in its class for offering all-wheel drive as a standard feature, and Subaru's traditional boxer engine. The Legacy was sold as the Liberty in Australia out of deference to Legacy Australia, an organisation dedicated to caring for the families of military service veterans. In 1996, a variant of the Legacy with heightened suspension called the Legacy Outback was introduced to compete in the burgeoning sport-utility vehicle class and proved to be a sales success for Subaru. The Outback line was split into its own model in 2008, known as the Subaru Outback. As of 2008, 3.6 million Legacy models have been built since its 1989 introduction. Production of the Legacy ended in Japan in June 2020, with the sixth-generation Legacy being last model being produced and marketed in Japan. First generation (BC/BF/BJ; 1989) The Legacy was introduced in 1989 to provide S ...
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Subaru Outback
The Subaru Outback is an automotive nameplate used by the Japanese automaker Subaru for two different vehicles: a crossover station wagon, the Outback (1994–present, also sold as in some markets), and an Impreza-derived hatchback, the Outback Sport (1994–2011). Most versions of the Outback wagon and Outback Sport have had all-wheel drive as standard equipment. Overview The original Outback station wagon was derived from the wagon variant of the second-generation Subaru Legacy. The first-generation Legacy, which made its debut in 1989, did not receive the cosmetic and suspension modifications to create an Outback version, although Subaru offered an Outdoor option package for the 1994 model year Legacy L all-wheel drive model, which added an compressed air strut height adjustable suspension, a luggage rack, a skidplate, and mud flaps. Earlier, a raised-roof "Touring Wagon" variant had been offered on the preceding Subaru Leone for the 1988 and 1989 model years. Subaru also ...
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Subaru Tribeca
The Subaru Tribeca is a mid-size crossover SUV made from 2005 to 2014. Released in some markets, including Canada, as the Subaru B9 Tribeca, the car derives its name from the Tribeca neighborhood of New York City. Built on the Subaru Legacy platform and sold in five- and seven-seat configurations, the Tribeca was intended to be sold alongside a slightly revised version known as the Saab 9-6X. Saab, at the time a subsidiary of General Motors (GM), abandoned the 9-6X program just prior to its release subsequent to GM's 2005 divestiture of its 20 percent stake in FHI. Inspired by the ''B9X'' concept car, the Tribeca's original design was criticized at launch and subsequently revised in 2007 for the 2008 model year, and the model name was shortened to simply ''Tribeca'' in all markets. Although not sold in Japan, North American markets received the Tribeca in 2005 for the 2006 model year, and it was introduced to Australasia and Europe in late 2006. In addition to these markets, the ...
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Active Valve Lift System
The I-Active Valve Lift System (i stands for intelligence) or i-AVLS is a valvetrain technology implemented by Subaru in the 2.5L naturally aspirated engines SOHC to improve emissions, efficiency and performance. Note that AVLS is different from AVCS used on other Subaru engines. AVLS improves performance and efficiency by changing which camshaft is operating which of the two intake valves. The camshafts on all AVLS Subaru engines have specially designed lobes for intake valves. They feature two different cam profiles: a low/mid lift profile or a high lift profile. The two intake valves in each cylinder are operated by a rocker arm with its own cam lobe. The cam utilized is selected by the 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 re ... (ECU). To select differen ...
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Exhaust Gas Recirculation
In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide () emissions reduction technique used in petrol/gasoline, diesel engines and some hydrogen engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. The exhaust gas displaces atmospheric air and reduces in the combustion chamber. Reducing the amount of oxygen reduces the amount of fuel that can burn in the cylinder thereby reducing peak in-cylinder temperatures. The actual amount of recirculated exhaust gas varies with the engine operating parameters. In the combustion cylinder, is produced by high-temperature mixtures of atmospheric nitrogen and oxygen, and this usually occurs at cylinder peak pressure. In a spark-ignition engine, an ancillary benefit of recirculating exhaust gases via an external EGR valve is an increase in efficiency, as charge dilution allows a larger throttle position and reduces associated pumping losses. Mazda's turbocharge ...
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Variable Valve Timing
In internal combustion engines, variable valve timing (VVT) is the process of altering the timing of a valve lift event, and is often used to improve performance, fuel economy or emissions. It is increasingly being used in combination with variable valve lift systems. There are many ways in which this can be achieved, ranging from mechanical devices to electro-hydraulic and camless systems. Increasingly strict emissions regulations are causing many automotive manufacturers to use VVT systems. Two-stroke engines use a power valve system to get similar results to VVT. Background theory The valves within an internal combustion engine are used to control the flow of the intake and exhaust gases into and out of the combustion chamber. The timing, duration and lift of these valve events has a significant impact on engine performance. Without variable valve timing or variable valve lift, the valve timing is the same for all engine speeds and conditions, therefore compromises are neces ...
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