A valve is a device or natural object that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically fittings, but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure. The word is derived from the Latin valva, the moving part of a door, in turn from volvere, to turn, roll.
A two-strokeengine is a type of internal combustion engine that completes a power cycle with two strokes of the piston during one power cycle, this power cycle being completed in one revolution of the crankshaft. A four-stroke engine requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust functions occurring at the same time.
A poppet valve is a valve typically used to control the timing and quantity of gas or vapor flow into or out of an engine, but with many other applications.
In an internal combustion engine, the cylinder head sits above the cylinders and forms the roof of the combustion chamber. In sidevalve engines, the head is a simple sheet of metal; whereas in more modern overhead valve and overhead camshaft engines, the cylinder head is a more complicated block often containing inlet and exhaust passages, coolant passages, valves, camshafts, spark plugs and fuel injectors. Most straight engines have a single cylinder head shared by all of the cylinders and most V engines have two cylinder heads.
A hemispherical combustion chamber is a type of combustion chamber in a reciprocating internal combustion engine with a domed cylinder head notionally in the approximate shape of a hemisphere. An engine featuring this type of hemispherical chamber is known as a hemi engine.
A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid to flow through it in only one direction.
The VR6 engines, commonly referred to as the “staggered six” is a 6-cylinder engine configuration developed by VW. The name VR6 comes from the combination of German words “Verkürzt” and “Reihenmotor” meaning “shortened inline engine”. It was developed specifically for transverse engine installations and FWD vehicles. The VR6 is a highly compact engine, thanks to the narrower angle of 10.5 to 15-degrees between cylinder banks, as opposed to the traditional V6 angles ranging from 45 to 90-degrees. The compact design is cheaper to manufacture, since only one cylinder head is required for all 6 cylinders, much like a traditional inline-6 engine.
A collet is a segmented sleeve, band or collar. One of the two radial surfaces of a collet is usually tapered and the other is cylindrical. The term collet commonly refers to a type of chuck that uses collets to hold either a workpiece or a tool but has other mechanical applications.
In internal combustion engines with carburetors, a choke valve or choke modifies the air pressure in the intake manifold, thereby altering the air–fuel ratio entering the engine. Choke valves are generally used in naturally aspirated engines to supply a richer fuel mixture when starting the engine. Most choke valves in engines are butterfly valves mounted upstream of the carburetor jet to produce a higher partial vacuum, which increases the fuel draw.
Bevel gears are gears where the axes of the two shafts intersect and the tooth-bearing faces of the gears themselves are conically shaped. Bevel gears are most often mounted on shafts that are 90 degrees apart, but can be designed to work at other angles as well. The pitch surface of bevel gears is a cone, known as a pitch cone. Bevel gears transfer the energy from linear to vertical power, making it very useful in machines widely used in mechanical settings.
Cylinder head porting refers to the process of modifying the intake and exhaust ports of an internal combustion engine to improve their air flow. Cylinder heads, as manufactured, are usually suboptimal for racing applications due to being designed for maximum durability. Ports can be modified for maximum power, minimum fuel consumption, or a combination of the two, and the power delivery characteristics can be changed to suit a particular application.
The intake/inlet over exhaust, or "IOE" engine, known in the US as F-head, is a four-stroke internal combustion engine whose valvetrain comprises OHV inlet valves within the cylinder head and exhaust side-valves within the engine block.
A valve job is an operation which is performed on any four stroke cycle, internal combustion engine, the purpose of which is to resurface the mating surfaces of the poppet valves and their respective valve seats that control the intake and exhaust of the air/fuel mixture that powers the motion of the pistons after the start cycle.
A valve guide is a cylindrical piece of metal, pressed or integrally cast into the cylinder head of most types of reciprocating engines, to positively locate a poppet valve so that it may make proper contact with its valve seat. Along with a corresponding valve spring, it is one of the components of any engine’s valve train.
The VR5 engines are a family of petroleum fuelled Internal combustion engines developed by the Volkswagen Group and produced from 1997 to 2006. They are derived from the VR6 engine family, also developed by Volkswagen, but with one less cylinder. The VR5 is a highly compact, thanks to the narrower angle of 15° and a displacement of 2,324 cc. The VR5 was the first production block to use five cylinders in a VR design with a 15-degree angle.
This article briefly describes the components and systems found in jet engines.
The Honda XBR 500 is a 500cc Japanese sports motorcycle launched by Honda in 1985 and in response to the Yamaha SR500. It is powered by a single-cylinder four-valve engine with the valve stem axes arranged radially relative to the geometric centre of the hemispherical combustion chamber - and actuated by rockers and intermediate sub-rockers. Displacing 498 cc (30.4 cu in) and producing 27 or 44 hp, the engine, having its origins in the Honda XR series off-road models, features a "quasi-dry sump", the bulk of the oil being stored in a separate tank below the seat but a proportion of the lubricant remaining in the crankcase sump. The steel-braided hoses connecting the oil tank to the engine are a strong visual element.
A bash valve is a valve within a piston engine, used to control the admission of the working fluid. They are directly actuated valves, operated by contact between the piston and the valve tip.
The mechanism of diving regulators is the arrangement of components and function of gas pressure regulators used in the systems which supply breathing gases for underwater diving. Both free-flow and demand regulators use mechanical feedback of the downstream pressure to control the opening of a valve which controls gas flow from the upstream, high-pressure side, to the downstream, low-pressure side of each stage. Flow capacity must be sufficient to allow the downstream pressure to be maintained at maximum demand, and sensitivity must be appropriate to deliver maximum required flow rate with a small variation in downstream pressure, and for a large variation in supply pressure, without instability of flow. Open circuit scuba regulators must also deliver against a variable ambient pressure. They must be robust and reliable, as they are life-support equipment which must function in the relatively hostile seawater environment, and the human interface must be comfortable over periods of several hours.
