Ram-air intake

Ram air intakes on a 1973 Mustang Mach 1

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]

Design features

Ram-air intake of a Porsche GT3 RS

Motorcycle with gooseneck mounted hypercharger air intake

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. 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 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.

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 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.

Aircraft

Pitot sensors are used to measure ram pressure, which is added to static pressure to derive the airspeed of an aircraft.

TA-4SU Super Skyhawk, note the ram-air intake mounted on the portside air intake for cooling the jet engine.
Mikoyan-Gurevich MiG-15
Diagram of piston engine with (from left to right): 1.) Ram-air intake, 2.) Air filter, 3.) mass flow sensor, 4.) butterfly valve, 5.) air box, 6.) intake runners, 7.) intake valve, 8.) piston, 9.) exhaust valve, 10.) extractor pipe, 11.) collector, 12.) catalytic converter, 13.) muffler.

References

↑ 1

Automotive engine

Part of the Automobile series

Basic terminology	Compression ratio Crank Cylinder Dead centre Diesel engine Dry sump Engine balance Engine configuration Engine displacement Engine knocking Firing order Hydrolock Petrol engine Power band Redline Spark-ignition engine Stroke Stroke ratio Wet sump

Main components	Connecting rod Crankcase Crankpin Crankshaft Crossflow cylinder head Crossplane Cylinder bank Cylinder block Cylinder head Flywheel Head gasket Hypereutectic piston Main bearing Piston Piston ring Reverse-flow cylinder head Starter ring gear Sump

Valvetrain	Cam Cam follower Camshaft Desmodromic valve Hydraulic tappet Multi-valve Overhead camshaft Overhead valve Pneumatic valve springs Poppet valve Pushrod Rocker arm Sleeve valve Tappet Timing belt Timing mark Valve float Variable valve timing

Aspiration	Air filter Blowoff valve Boost controller Butterfly valve Centrifugal-type supercharger Cold air intake Dump valve Electronic throttle control Forced induction Inlet manifold Intake Intercooler Manifold vacuum Naturally aspirated engine Ram-air intake Scroll-type supercharger Short ram air intake Supercharger Throttle Throttle body Turbocharger Twin-turbo Variable-geometry turbocharger Variable-length intake manifold Warm air intake

Fuel system	Carburetor Common rail Direct injection Fuel filter Fuel injection Fuel pump Fuel tank Gasoline direct injection Indirect injection Injection pump Lean-burn Stratified charge engine Turbo fuel stratified injection Unit injector

Ignition	Contact breaker Magneto Distributor Electrical ballast High tension leads Ignition coil Spark plug Wasted spark

Electrics and engine management	Air–fuel ratio meter Alternator Automatic Performance Control Car battery (lead–acid battery) Crankshaft position sensor Dynamo Drive by wire Electronic control unit Engine control unit Engine coolant temperature sensor Glow plug Idle air control actuator MAP sensor Mass flow sensor Oxygen sensor Starter motor Throttle position sensor

Exhaust system	Automobile emissions control Catalytic converter Diesel particulate filter Exhaust manifold Glasspack Muffler

Engine cooling	Air cooling Antifreeze (ethylene glycol) Core plug Electric fan Fan belt Radiator Thermostat Water cooling Viscous fan (fan clutch)

Other components	Balance shaft Block heater Combustion chamber Cylinder head porting Gasket Motor oil Oil filter Oil pump Oil sludge PCV valve Seal Synthetic oil Underdrive pulleys

Portal Category

^[1]

↑ motociclismo.es. "ram air". motociclismo. Retrieved 13 June 2015.

This article is issued from Wikipedia - version of the Saturday, June 13, 2015. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.

Ram-air intake

Design features

Aircraft

See also

References