A four-strokeengine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The four separate strokes are termed:
- Intake: Also known as induction or suction. This stroke of the piston begins at top dead center (T.D.C.) and ends at bottom dead center (B.D.C.). In this stroke the intake valve must be in the open position while the piston pulls an air-fuel mixture into the cylinder by producing a partial vacuum in the cylinder through its downward motion.
- Compression: This stroke begins at B.D.C, or just at the end of the suction stroke, and ends at T.D.C. In this stroke the piston compresses the air-fuel mixture in preparation for ignition during the power stroke (below). Both the intake and exhaust valves are closed during this stage.
- Combustion: Also known as power or ignition. This is the start of the second revolution of the four stroke cycle. At this point the crankshaft has completed a full 360 degree revolution. While the piston is at T.D.C. the compressed air-fuel mixture is ignited by a spark plug or by heat generated by high compression, forcefully returning the piston to B.D.C. This stroke produces mechanical work from the engine to turn the crankshaft.
- Exhaust: Also known as outlet. During the exhaust stroke, the piston, once again, returns from B.D.C. to T.D.C. while the exhaust valve is open. This action expels the spent air-fuel mixture through the exhaust port.
The vacuum brake is a braking system employed on trains and introduced in the mid-1860s. A variant, the automatic vacuum brake system, became almost universal in British train equipment and in countries influenced by British practice. Vacuum brakes also enjoyed a brief period of adoption in the United States, primarily on narrow-gauge railroads. Their limitations caused them to be progressively superseded by compressed air systems starting in the United Kingdom from the 1970s onward. The vacuum brake system is now obsolete; it is not in large-scale usage anywhere in the world, other than in South Africa, largely supplanted by air brakes.
Fluid power is the use of fluids under pressure to generate, control, and transmit power. Fluid power is conventionally subdivided into hydraulics and pneumatics. Although steam is also a fluid, steam power is usually classified separately from fluid power. Compressed-air and water-pressure systems were once used to transmit power from a central source to industrial users over extended geographic areas; fluid power systems today are usually within a single building or mobile machine.
Variable valve timing (VVT) is the process of altering the timing of a valve lift event in an internal combustion engine, 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.
VVT-i, or Variable Valve Timing with intelligence, is an automobile variable valve timing technology developed by Toyota. It was introduced in 1995 with the 2JZ-GE engine found in the JZS155 Toyota Crown and Crown Majesta.
Variable camshaft timing (VCT) is an automobile variable valve timing technology developed by Ford. It allows for more optimum engine performance, reduced emissions, and increased fuel efficiency compared to engines with fixed camshafts. It uses electronically controlled hydraulic valves that direct high pressure engine oil into the camshaft phaser cavity. These oil control solenoids are bolted into the cylinder heads towards the front of the engine near the camshaft phasers. The powertrain control module (PCM) transmits a signal to the solenoids to move a valve spool that regulates the flow of oil to the phaser cavity. The phaser cavity changes the valve timing by rotating the camshaft slightly from its initial orientation, which results in the camshaft timing being advanced. The PCM adjusts the camshaft timing depending on factors such as engine load and RPM.
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.
The GM Ecotec engine, also known by its codename L850, is a family of all-aluminium inline-four engines, displacing between 1.4 and 2.5 litres. Confusingly, the Ecotec name was also applied to both the Buick V6 Engine when used in Holden Vehicles, as well as the final DOHC derivatives of the previous GM Family II engine; the architecture was substantially re-engineered for this new Ecotec application produced since 2000. This engine family replaced the GM Family II engine, the GM 122 engine, the Saab H engine, and the Quad 4 engine. It is manufactured in multiple locations, to include Spring Hill Manufacturing, in Spring Hill, Tennessee, with engine blocks and cylinder heads cast at Saginaw Metal Casting Operations in Saginaw, Michigan.
A compression release engine brake, compression brake, or decompression brake is an engine braking mechanism installed on some diesel engines. When activated, it opens exhaust valves to the cylinders, right before the compression stroke ends, releasing the compressed gas trapped in the cylinders, and slowing the vehicle.
In automotive engineering, an exhaust manifold collects the exhaust gases from multiple cylinders into one pipe. The word manifold comes from the Old English word manigfeald and refers to the folding together of multiple inputs and outputs.
Engine braking occurs when the retarding forces within an internal combustion engine are used to slow down a motor vehicle, as opposed to using additional external braking mechanisms such as friction brakes or magnetic brakes.
An inlet manifold or intake manifold is the part of an internal combustion engine that supplies the fuel/air mixture to the cylinders. The word manifold comes from the Old English word manigfeald and refers to the multiplying of one (pipe) into many.
Hydraulic machines use liquid fluid power to perform work. Heavy construction vehicles are a common example. In this type of machine, hydraulic fluid is pumped to various hydraulic motors and hydraulic cylinders throughout the machine and becomes pressurized according to the resistance present. The fluid is controlled directly or automatically by control valves and distributed through hoses, tubes, or pipes.
A wastegate is a valve that controls the flow of exhaust gases to the turbine wheel in a turbocharged engine system.
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.
Homogeneous Charge Compression Ignition (HCCI) is a form of internal combustion in which well-mixed fuel and oxidizer are compressed to the point of auto-ignition. As in other forms of combustion, this exothermic reaction produces heat that can be transformed into work in a heat engine.
A retarder is a device used to augment or replace some of the functions of primary friction-based braking systems, usually on heavy vehicles. Retarders serve to slow vehicles, or maintain a steady speed while traveling down a hill, and help prevent the vehicle from unintentional or uncontrolled acceleration when travelling on a road surface with an uneven grade. They are not usually capable of bringing vehicles to a standstill, as their effectiveness diminishes as a vehicle's speed lowers. Instead, they are typically used as an additional aid to slow vehicles, with the final braking done by a conventional friction braking system. An additional benefit retarders are capable of providing is an increase in the service life of the friction brake, as it is subsequently used less frequently, particularly at higher speeds. Additionally, air actuated brakes serve a dual role in conserving air pressure.
The Volvo FE is a medium duty truck produced by Volvo Trucks Corporation since 2006, now in its second generation. The FE is available in various rigid versions and a tractor version spanning three weight classes.
Jacobs Vehicle Systems, Inc. is an American company that engineers, develops and manufacturers commercial vehicle retarding and valve actuation technologies. The company produces light-duty, medium-duty, and heavy-duty engine brakes, recreational vehicle exhaust brakes, aftermarket parts and tune-up kits to heavy-duty diesel engine manufacturers in its domestic market in America, as well as in Asia and Europe. The company was incorporated in 1990 and is based in Bloomfield, Connecticut. Jacobs Vehicle Systems, Inc. operates as a subsidiary of Altra Industrial Motion Corporation. On 9 February 2022, Cummins, Inc. announced an agreement to acquire Jacobs Vehicle Systems from Altra.
An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.
