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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. [1]
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. [2] [3] 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 intakes 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.
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.
The short ram air intake is a form of aftermarket air intake for automobiles with internal combustion engines.
It replaces the OEM air intake with a short metal pipe and a conical air filter inside the engine bay. A significant increase in intake air volume will only occur in an engine where the factory intake piping was designed with baffles and other sound absorbing materials (rubber, etc.).
The term ram, albeit commonly used, is somewhat a misnomer. A true ram air intake device is something that enhances intake pressure or in the case of resonant systems such as Chrysler's Sonaramic, increases the torque with a peak at a certain RPM.
There is still some open debate on this issue, but some believe that a problem with short ram air intakes is that the air entering the intake is at a higher temperature due to the proximity of the engine, which may reduce some power. This may be partially offset by an increase in the volume of air entering the engine. To counter intake heat problems, many short ram intakes include some form of heat shield. Moving the intake inlet port further away from the engine block will also help to alleviate the problem and some users use a cold air intake where the inlet air is at or close to ambient temperature. However, others claim that Short Ram Intakes (SRIs) or similar Warm Air Intakes (WAIs) offer benefits over Cold Air Intakes (CAIs) which include better MPG due to a more complete burning of fuel. Users with forced induction engines often opt for short ram intakes because compressors adjacent to the engine, especially turbochargers, heat the incoming air and negate much of the benefits of a cold air intake. Additional problems can result from using a short ram intake in cars utilizing a mass airflow sensor though most of today's sensors automatically adjust without issue. Turbulence in the intake airflow produced by the filter or piping, or a change in intake diameter at the point where the airflow is measured can produce inaccurate airflow readings. The error in airflow then translates to an error in the amount of added fuel. In the worst case, the air-fuel ratio can run lean, causing detonation and possibly engine failure although the airflow sensor will generally detect and correct the throttle to compensate for the warmer air. This can also be solved by modifying/elongating the intake piping, replacing the airflow meter, or by replacing/remapping the engine control computer to provide the correct amount of fuel for the intake airflow at all engine speeds.
A harmless but noticeable result of using a short ram air intake is an increase in intake noise, which may manifest as a sucking sound, and the loss of any silencing properties that the factory intake had.
Pitot sensors are used to measure ram pressure which, along with static pressure, is used to estimate the airspeed of an aircraft.
A turbocharger, colloquially known as a turbo, is a turbine-driven, forced induction device that increases an internal combustion engine's efficiency and power output by forcing extra compressed air into the combustion chamber. This improvement over a naturally aspirated engine's power output is because the compressor can force more air—and proportionately more fuel—into the combustion chamber than atmospheric pressure alone.
Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of an injector.
A carburetor or carburettor is a device that mixes air and fuel for internal combustion engines in the proper air–fuel ratio for combustion. It is sometimes colloquially shortened to carb in the UK and North America or carby in Australia. To carburate or carburet means to mix the air and fuel or to equip with a carburetor for that purpose.
Engine tuning is the adjustment or modification of the internal combustion engine or Engine Control Unit (ECU) to yield optimal performance and increase the engine's power output, economy, or durability. These goals may be mutually exclusive; an engine may be de-tuned with respect to output power in exchange for better economy or longer engine life due to lessened stress on engine components.
Aircraft engine controls provide a means for the pilot to control and monitor the operation of the aircraft's powerplant. This article describes controls used with a basic internal-combustion engine driving a propeller. Some optional or more advanced configurations are described at the end of the article. Jet turbine engines use different operating principles and have their own sets of controls and sensors.
A cold air intake (CAI) is usually an aftermarket assembly of parts used to bring relatively cool air into a car's internal-combustion engine.
A blow-off valve (BOV), dump valve or compressor bypass valve (CBV), is a pressure release system present in most turbocharged engines. Its main purpose is to take the load off the turbocharger when the throttle is suddenly closed.
In automotive engineering, an inlet manifold or intake manifold is the part of an 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.
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.
An intake is an opening, structure or system through which a fluid is admitted to a space or machine as a consequence of a pressure differential between the outside and the inside. The pressure difference may be generated on the inside by a mechanism, or on the outside by ram pressure or hydrostatic pressure. Flow rate through the intake depends on pressure difference, fluid properties, and intake geometry.
The manifold absolute pressure sensor is one of the sensors used in an internal combustion engine's electronic control system.
A mass (air) flow sensor (MAF) is a sensor used to determine the mass flow rate of air entering a fuel-injected internal combustion engine.
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, 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.
Carburetor, carburettor, carburator, carburettor heat is a system used in automobile and piston-powered light aircraft engines to prevent or clear carburetor icing. It consists of a moveable flap which draws hot air into the engine intake. The air is drawn from the heat stove, a metal plate around the exhaust manifold.
A boost controller is a device to control the boost level produced in the intake manifold of a turbocharged or supercharged engine by affecting the air pressure delivered to the pneumatic and mechanical wastegate actuator.
A throttle is the mechanism by which fluid flow is managed by constriction or obstruction.
The Quadrajet is a four barrel carburetor, made by the Rochester Products Division of General Motors. Its first application was the new-for-1965 Chevy 396ci engine. Its last application was on the 1990 Oldsmobile 307 V8 engine, which was last used in the Cadillac Brougham and full size station wagons made by Chevrolet, Pontiac, Oldsmobile, and Buick.
A velocity stack', 'trumpet, or air horn, is a trumpet-shaped device of differing lengths which is fitted to the air entry of an engine's intake system, carburetor or fuel injection.
This article briefly describes the components and systems found in jet engines.
Of the three types of carburetors used on large, high-performance aircraft engines manufactured in the United States during World War II, the Bendix-Stromberg pressure carburetor was the one most commonly found. The other two carburetor types were manufactured by Chandler Groves and Chandler Evans Control Systems (CECO). Both of these types of carburetors had a relatively large number of internal parts, and in the case of the Holley Carburetor, there were complications in its "variable venturi" design.