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Variable Valve Lift
Variable valve lift (VVL) is an automotive piston engine technology which varies the height a valve opens in order to improve performance, fuel economy or emissions. There are two main types of VVL: discrete, which employs fixed valve lift amounts, and continuous, which is able to vary the amount of lift. Continuous valve lift systems typically allow for the elimination of the throttle valve. When used in conjunction with variable valve timing (VVT), variable valve lift can potentially offer infinite control over the intake and exhaust valve timing. History In 1958 Porsche made application for a German patent, also applied for and published as British Patent GB861369 in 1959. The Porsche patent used an oscillating cam to increase the valve lift and duration. The desmodromic cam driven via a push/pull rod from an eccentric shaft or swashplate. It is unknown if any working prototype was ever made. Fiat was the first auto manufacturer to patent a functional automotive variable valve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Piston Engine
A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common features of all types. The main types are: the internal combustion engine, used extensively in motor vehicles; the steam engine, the mainstay of the Industrial Revolution; and the Stirling engine for niche applications. Internal combustion engines are further classified in two ways: either a spark-ignition (SI) engine, where the spark plug initiates the combustion; or a compression-ignition (CI) engine, where the air within the cylinder is compressed, thus heating it, so that the heated air ignites fuel that is injected then or earlier.''Thermodynamics: An Engineering Approach'' by Yunus A. Cengal and Michael A. Boles Common features in all types There may be one or more pistons. Each piston is inside a cylinder, into which a gas is intro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VarioCam
VarioCam is an automobile variable valve timing technology developed by Porsche. VarioCam varies the timing of the intake valves by adjusting the tension on the timing chain connecting the intake and exhaust camshafts. VarioCam was first used on the 1992 3.0 L engine in the Porsche 968. Porsche's more recent VarioCam Plus combines variable valve timing with two-stage lift on the intake side. The two-stage valve-lift function is performed by electro-hydraulically operated switchable tappets. Each of these 12 tappets consists of concentric lifters which can be locked together by means of a pin. The inner lifter is actuated by a small cam lobe, while the outer ring element is moved by a pair of larger-profile lobes. The timing of each valve is seamlessly adjusted by means of an electro-hydraulically operated rotary vane adjuster at the head of each intake camshaft. Valve timing and the valve profile are continuously altered according to conditions and engine load. For improved r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Camless
A camless or free-valve piston engine is an engine that has poppet valves operated by means of electromagnetic, hydraulic, or pneumatic actuators instead of conventional cams. Actuators can be used to both open and close valves, or to open valves closed by springs or other means. Camshafts normally have one lobe per valve, with a fixed valve duration and lift. Although many modern engines use camshaft phasing, adjusting the lift and valve duration in a working engine is more difficult. Some manufacturers use systems with more than one cam lobe, but this is still a compromise as only a few profiles can be in operation at once. This is not the case with the camless engine, where lift and valve timing can be adjusted freely from valve to valve and from cycle to cycle. It also allows multiple lift events per cycle and, indeed, no events per cycle—switching off the cylinder entirely. Camless development Camless valve trains have long been investigated by several companies, including ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable Displacement
Variable displacement is an automobile engine technology that allows the engine displacement to change, usually by deactivating cylinders, for improved fuel economy. The technology is primarily used in large, multi-cylinder engines. Many automobile manufacturers have adopted this technology as of 2005, although the concept has existed for some time prior to this. Theory of operation Cylinder deactivation is used to reduce the fuel consumption and emissions of an internal combustion engine during light-load operation. In typical light-load driving the driver uses only around 30 percent of an engine’s maximum power. In these conditions, the throttle valve is nearly closed, and the engine needs to work to draw air. This causes an inefficiency known as pumping loss. Some large capacity engines need to be throttled so much at light load that the cylinder pressure at top dead centre is approximately half that of a small 4-cylinder engine. Low cylinder pressure results in lower fuel e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Valvematic
VVT-i, or Variable Valve Timing with intelligence, is an automobile variable valve timing technology developed by Toyota. It was first introduced in 1995 with the ''2JZ-GE'' engine found in the JZS155 Toyota Crown and Crown Majesta. The VVT-i system replaces the Toyota VVT system first introduced in 1991 with the five-valve per cylinder '' 4A-GE'' engine found in the AE101 Corolla Levin and Sprinter Trueno. The VVT system is a 2-stage hydraulically controlled cam phasing system. VVT-i varies the timing of the intake valves by adjusting the relationship between the camshaft drive (belt or chain) and intake camshaft. Engine oil pressure is applied to an actuator to adjust the camshaft position. Adjustments in the overlap time between the exhaust valve closing and intake valve opening result in improved engine efficiency. Variants of the system, including VVTL-i, Dual VVT-i, VVT-iE, VVT-iW and Valvematic, have followed. VVTL-i VVTL-i (Variable Valve Timing and Lift intellig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable Valve Event And Lift
Nissan Variable Valve Event and Lift (commonly abbreviated as VVEL) is an automobile variable valve timing technology developed by Nissan. Nissan VVEL was first introduced to the US market in late-2007 on the 2008 Infiniti G37 Coupe sporting the new "VVEL" VQ37VHR engine (VQ37VHR motor specs: 11.0:1 CR, 95.5mm bore, 86mm stroke, 7500rpm redline). VVEL variable valve timing is also used in the VK50VE V8 engine from the Infiniti FX50. A rocker arm and two types of links open the intake-valves by transferring the rotational movement of a drive shaft with an eccentric cam to the output cam. The movement of the output cam is varied by rotating the control shaft with a DC stepper motor and changing the fulcrums of the links. This makes the continuous adjustment of the amount of the valve's lift (e.g., the amount of intake opening), during the intake valve event in the four-stroke cycle, possible. CVTC and VVEL together control the valve phases and its valve events, allowing free-con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Advanced VTEC
VTEC (Variable Valve Timing & Lift Electronic Control) is a system developed by Honda to improve the volumetric efficiency of a four-stroke internal combustion engine, resulting in higher performance at high RPM, and lower fuel consumption at low RPM. The VTEC system uses two (or occasionally three) camshaft profiles and hydraulically selects between profiles. It was invented by Honda engineer Ikuo Kajitani. It is distinctly different from standard VVT (variable valve timing) systems which change only the valve timings and do not change the camshaft profile or valve lift in any way. Context and description Japan levies a tax based on engine displacement, and Japanese auto manufacturers have correspondingly focused their research and development efforts toward improving the performance of their smaller engine designs. One method for increasing performance into a static displacement includes forced induction, as with models such as the Toyota Supra and Nissan 300ZX which us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Throttle
A throttle is the mechanism by which fluid flow is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases (by the use of a throttle), but usually decreased. The term ''throttle'' has come to refer, informally, to any mechanism by which the power or speed of an engine is regulated, such as a car's accelerator pedal. What is often termed a ''throttle'' (in an aviation context) is also called a thrust lever, particularly for jet engine powered aircraft. For a steam locomotive, the valve which controls the steam is known as the regulator. Internal combustion engines In an internal combustion engine, the throttle is a means of controlling an engine's power by regulating the amount of fuel or air entering the engine. In a motor vehicle the control used by the driver to regulate power is sometimes called the throttle, accelerator, or gas Automobile pedal, pedal. For a gasoline engine, the throttle most commonly regul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VANOS
VANOS is a variable valve timing system used by BMW on various automotive petrol engines since 1992. The name is an abbreviation of the German words for ''variable camshaft timing'' (german: variable Nockenwellensteuerung). The initial version (retrospectively renamed "single VANOS") was solely used on the intake camshaft, while the later "double VANOS" systems are used on intake and exhaust camshafts. Since 2001, VANOS is often used in conjunction with the valvetronic variable valve lift system. Operation VANOS is a variator system that varies the timing of the valves by moving the position of the camshafts in relation to the drive gear. The relative timing between inlet and exhaust valves is changed. At lower engine speeds, the position of the camshaft is moved so the valves are opened later, as this improves idling quality and smooth power development. As the engine speed increases, the valves are opened earlier: this enhances torque, reduces fuel consumption and lowers emi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Valvetronic
The Valvetronic system is a BMW variable valve lift system which, in combination with VANOS, allows infinite adjustment of the intake valve timing and duration. The system claims to improve fuel economy and emissions, and negates the need for a throttle body in regular use. First introduced by BMW on the 316ti compact in 2001, Valvetronic has since been added to many of BMW's engines. The first application of this technology in a turbocharged engine was the N55 engine. See also * VANOS: BMW's variable valve timing * Prince engine Prince is the codename for a family of straight-four 16-valve all-aluminium gasoline engines with variable valve lift and variable valve timing developed by PSA Peugeot Citroën and BMW. It is a compact engine family of 1.4–1.6 L in disp ... References Variable valve timing BMW {{Auto-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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