Installing a cool air intake or a warm air intake (also known as a short ram) is a popular way to increase the power output of any car’s engine without doing serious modifications. These two designs share quite a few similarities and they add to your engine’s power rating by applying the same basic principles.
As a general rule, both of these types of intake systems come equipped with a high-flow filter design of some kind. This alone can increase the power potential of your car’s engine quite a bit, sometimes up to 5 percent. The stock air filter is often one of the biggest obstructions of the intake path; it drastically limits airflow and reduces fresh air infiltration. Cold air and short ram intake designs replace the stock air filtration system with a high flow cone filter, which usually has an increased surface area over stock designs. Also, high flow filters generally use an oiled cotton or similar filter element to replace the stock design’s paper filter.
As mentioned earlier, the way cold air and short ram intake systems function is by removing restriction from the intake path. The more air your car can draw in and mix with fuel, the more power it is able to make. Generally these systems include aftermarket intake piping manufactured from aluminum or other more rigid material. Since the aluminum piping is smoother inside than the stock intake, it reduces turbulence in the intake stream. This allows the engine to maintain a high-velocity and low-turbulence flow of air.
The biggest advantage a cold-air intake has over a short-ram intake is that it allows the motor to pull in colder air from a location away from the heat of the engine. The temperature of the air under the hood rises due to residual heat from the radiator and cooling system. A cold air intake avoids this by using air from another location, such as the spaces around the wheel wells or inside the front bumper. This increases the power potential of the intake charge. The reason is simple: cold air is denser than heated air.
Since we already know more fuel mixed with more air equals more power by using cooler, denser air, a cold air intake is able to add more fuel per-unit-volume of air. This is especially important when the car is moving slowly or starting from a stop. When the car isn’t moving, hot air gathers underneath the hood. A short ram intake is forced to use this heated air for the intake charge, which means it loses power. The cold air style intake isn’t affected as much under these conditions. However once the car is moving, the difference in performance between the two is much less noticeable since the temperature under the hood drops considerably.