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. In some cars the intake is placed behind the radiator, where not only the air is hot, but the pressure is below ambient pressure. Thus a ram-air intake also is a cold air intake. The lack of losses also means without heating the air.

Given that the air velocity is reduced to zero without losses the pressure increase can be calculated accordingly. As the pressurised ram-air may kill this venturi effect, the carburetor needs to be designed to take this into account, or, alternatively, the engine may need fuel-injection.Īt low speeds (subsonic speeds) increases in static pressure are however limited to a few percent. 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. It fell out of favor in the seventies, but recently made a comeback.

Ram-air was a feature on some cars in the sixties. The 1990 Kawasaki Ninja ZX-11 C1 model used a ram-air intake, the very first on any production motorcycle. Ram-air systems are used on high-performance vehicles, most often on motorcycles and performance cars. 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. When gas velocity goes down the dynamic pressure is reduced, while the static pressure is increased. The ram-air intake works by reducing the intake air velocity by increasing the cross-sectional area of the intake ducting. Motorcycle with gooseneck mounted hypercharger air intake

Ram pressure compensating