A cold air intake is a system used to bring down the temperature of the air going into a car with the purpose of increasing the power of the internal-combustion engine. A secondary goal is to increase the appeal of a car by changing the appearance of a car's engine bay and creating an attractive intake noise. The first air intake systems were offered and consisted of molded plastic intake tubes and a cone-shaped cotton gauze air filter. Overseas manufacturers began importing popular Japanese air intake system designs for the sport compact market. Intake systems are now available in metal tube designs, allowing a greater degree of customization. The tubes are typically powder-coated or painted to match a vehicle. Cold air intake systems operate on the principle of increasing the amount of oxygen available for combustion with fuel. Because cooler air has higher volume density, cold air intakes generally work by introducing cooler air from outside the hot engine bay. However, the term "cold air intake" is often used to describe other methods of increasing oxygen to an engine, which may even increase the temperature of the air coming into an engine. • Increased air intake diameter for increased airflow • Interior intake smoothing to reduce air resistance • Direct route provision to air intake • Intake length tuning providing maximum RPM airflow • More efficient, less restricting air filters • Intake systems come in many different styles and can be constructed from plastic, metal, rubber or composite materials. • Due to the limited time air actually remains inside the intake tubing, the materials often do not impact a kit's ability to deliver cool air. • The most efficient intake systems utilize an airbox which is sized to compliment the engine and will extend the powerband of the engine. • The intake snorkel (opening for the intake air to enter the system) must be large enough to ensure sufficient air is available to the engine under all conditions from idle to full throttle. • If the intake opening has an unrestricted opening - no screens or other obstructions - the opening need not be larger than the inside diameter of the engine's throttle body, airhorn, or carburetor throat. • Under some conditions, intake system efficiency can be lost if the intake opening for the airbox is too large. • The most basic cold air intake replaces the stock airbox with a short metal or plastic tube leading to a conical air filter, called a Short ram air intake. • The power gained by this method can vary depending on how restrictive the factory airbox is. • The placement of the filter is usually directly in the engine compartment. • The overall benefits depend on the specific application. • Power may be lost at certain engine speeds, and gained at others. • Because of the increased airflow and reduced covering, intake noise is usually increased. • This effect is usually amplified on applications where a resonator, a part intended to reduce intake noise on some vehicles, is replaced by the intake. Well designed intakes use heat shields to isolate the air filter from the rest of the engine compartment, providing cooler air from the front or side of the engine bay. Carbon fiber can be used for the piping instead of metal, reducing weight and insulating the air from the engine bay in some cases. Carbon fiber and other advanced composites are expensive, and can be more cosmetic than functional. The most extreme designs, sometimes referred to as Complete Cold Air (CCA) intakes, route air from outside the engine bay, usually from the wheel wells, front grill,or a hood scoop. The intake can be placed such that the forward motion of the car pressurizes the air coming in, creating a ram-air intake. These intakes often require additional modifications and can require body modifications or replacement panels, such as a replacement "ram air-style" hood. Complete Cold Air intakes can convert to short ram intakes for winter or wet driving. When using a cold air intake, there is a potential risk when driving in the rain. This is often referred to as "hydrolock". Because your engine is getting air from inside your bumper you have to be careful when driving in the rain. If your engine sucks up any amount of water through the intake and into the engine you will probably have little to no horsepower left. In more extreme cases, the water brought into the engine through the intake can actually break connecting rods in the pistons, as water will not compress at all, unlike air. Avoiding getting water in the engine may include installing a water shield into the intake or not driving in the rain at all and less water damage occurs on a rotary engine car, as opposed to a piston engine car. Some cold air intake manufacturers now include a built in hydro-shield. This piece of plastic blocks water from entering the air filter and prevents hydrolock. Air bypass valves are a filtered spacer positioned into the engine bay, between two connected pieces of the cold air intake assembly, preventing hydro-locking by providing an alternate route for air to enter and eliminating the vacuum that causes water to be sucked in from a puddle. Although this simple, valveless, air permeable piece of foam may reduce power, it also provides more surface area for air entering the engine upon acceleration. When driving at moderate speeds, the suction caused by the engine is not enough to activate the air bypass valve. Cloth filter bypass valves allow air to enter if the valve is sucked open as result of vacuum pressure caused by a blocked filter at the bottom of the intake.