Ram-air intake
Encyclopedia
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 engine, thus allowing a greater massflow through the engine and hence increasing engine power.
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 this higher pressure gives.
Ram-air systems are used on high-performance vehicles, most often on motorcycle
s and performance cars. 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 may increase the volumetric efficiency
of an engine, they can be difficult to combine with carburetters, which rely on a venturi
-engendered pressure drop to draw fuel through the main jet. As the pressurised ram-air may kill this venturi effect, the carb will need to be designed to take this into account; or the engine may need fuel-injection.
Modern parachutes and kites use a ram-air system to pressurize a series of cells to provide the aerofoil shape.
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 according. 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 filter
s, high flow mass flow sensor
s, velocity stacks, tuned air box and large tubes from the filter to the engine.
sensors are used to measure ram pressure, which is added to static pressure to derive the airspeed
of an aircraft.
Intake
An intake , or especially for aircraft inlet, is an air intake for an engine. Because the modern internal combustion engine is in essence a powerful air pump, like the exhaust system on an engine, the intake must be carefully engineered and tuned to provide the greatest efficiency and power...
design which uses the dynamic air pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
created by vehicle motion to increase the static air pressure inside of the intake manifold on an engine, thus allowing a greater massflow through the engine and hence increasing engine power.
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 this higher pressure gives.
Ram-air systems are used on high-performance vehicles, most often on motorcycle
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...
s and performance cars. 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 may increase the volumetric efficiency
Volumetric efficiency
Volumetric efficiency in internal combustion engine design refers to the efficiency with which the engine can move the charge into and out of the cylinders. More specifically, volumetric efficiency is a ratio of what quantity of fuel and air actually enters the cylinder during induction to the...
of an engine, they can be difficult to combine with carburetters, which rely on a venturi
Venturi effect
The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe. The Venturi effect is named after Giovanni Battista Venturi , an Italian physicist.-Background:...
-engendered pressure drop to draw fuel through the main jet. As the pressurised ram-air may kill this venturi effect, the carb will need to be designed to take this into account; or the engine may need fuel-injection.
Modern parachutes and kites use a ram-air system to pressurize a series of cells to provide the aerofoil shape.
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 according. The lack of losses also means without heating the air. Thus a ram-air intake also is a cold air intake
Cold air intake
A cold air intake is an aftermarket assembly of parts used to bring relatively cool air into a car's internal-combustion engine.Most vehicles manufactured since the mid-1970s have thermostatic air intake systems that regulate the temperature of the air entering the engine's intake tract, providing...
. 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 filter
Air filter
A particulate air filter is a device composed of fibrous materials which removes solid particulates such as dust, pollen, mold, and bacteria from the air. A chemical air filter consists of an absorbent or catalyst for the removal of airborne molecular contaminants such as volatile organic compounds...
s, high flow mass flow sensor
Mass flow sensor
A mass air flow sensor is used to find out the mass flowrate of air entering a fuel-injected internal combustion engine. The air mass information is necessary for the engine control unit to balance and deliver the correct fuel mass to the engine. Air changes its density as it expands and contracts...
s, velocity stacks, tuned air box and large tubes from the filter to the engine.
Aircraft
PitotPitot tube
A pitot tube is a pressure measurement instrument used to measure fluid flow velocity. The pitot tube was invented by the French engineer Henri Pitot Ulo in the early 18th century and was modified to its modern form in the mid-19th century by French scientist Henry Darcy...
sensors are used to measure ram pressure, which is added to static pressure to derive the airspeed
Airspeed
Airspeed is the speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are: indicated airspeed , calibrated airspeed , true airspeed , equivalent airspeed and density airspeed....
of an aircraft.
See also
- Air filterAir filterA particulate air filter is a device composed of fibrous materials which removes solid particulates such as dust, pollen, mold, and bacteria from the air. A chemical air filter consists of an absorbent or catalyst for the removal of airborne molecular contaminants such as volatile organic compounds...
- BoosterBoosterBooster may refer to:In science and technology:* Booster , a motor-generator set used for voltage regulation in direct current electrical power circuits...
- RamjetRamjetA ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of airbreathing jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed and thus cannot move an aircraft from a standstill...
- SuperchargerSuperchargerA supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...
- TurbochargerTurbochargerA turbocharger, or turbo , from the Greek "τύρβη" is a centrifugal compressor powered by a turbine that is driven by an engine's exhaust gases. Its benefit lies with the compressor increasing the mass of air entering the engine , thereby resulting in greater performance...
- Cold air intakeCold air intakeA cold air intake is an aftermarket assembly of parts used to bring relatively cool air into a car's internal-combustion engine.Most vehicles manufactured since the mid-1970s have thermostatic air intake systems that regulate the temperature of the air entering the engine's intake tract, providing...
- Warm air intakeWarm air intakeFor other uses, see Warm air intake .A heated air inlet or warm air intake is a system commonly used on the original air cleaner assemblies of carburetted engines to increase the temperature of the air going into the engine for the purpose of increasing the consistency of mixing of the air and fuel...
- Short ram air intakeShort ram air intakeThe short ram air intake is a form of aftermarket air intake for automobiles with internal combustion engines.It basically replaces the OEM air intake with a short metal pipe and a conical air filter inside the engine bay...
- Diffuser (automotive)Diffuser (automotive)A diffuser, in an automotive context, is a shaped section of the car underbody which improves the car's aerodynamic properties by enhancing the transition between the high-velocity airflow underneath the car and the much slower freestream airflow of the ambient atmosphere...