Cold air intake
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Standard air intake systems tend to be very restrictive sacrificing engine power or efficiency in order to eliminate engine noise. Aftermarket cold air intake systems come in many different colors and sizes, and are easy to install when compared with other performance-increasing modifications. All cold air intakes operate on the principle of increasing the amount of oxygen available for combustion with fuel. Because cooler air has a higher density (greater mass per unit volume), cold air intakes generally work by introducing cooler air from outside the hot engine bay. However, the term "cold air intake" is often used incorrectly to describe an air filter system with an exposed filter in the engine bay, which actually increases the temperature of the air entering an engine.
Some strategies used in designing cold-air intakes are:
- Smoothing the interior of the intake to reduce air resistance.
- Providing a more direct route to the air intake by eliminating muffling devices.
- Shortening the length of the intake.
- Using a less restrictive air filter, usually trading filtering quality for increased airflow capacity.
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Advantages
Other advantages to having a cold air intake installed include:- Increased horsepower and torque - As a cold air intake draws in a higher volume of air which may be much cooler, your engine can breathe easier than with a limiting stock system. With your combustion chamber filled by cooler, oxygen-rich air, fuel burns at a more efficient mixture. You get more power and torque out of every drop of fuel when it's combined with the right amount of air.
- Improved throttle response and fuel economy in most cases - Stock intakes often deliver warmer, fuel-rich combustion mixtures that cause your engine to lose power and responsiveness while running hotter and more sluggishly. Cold air intakes can help your fuel economy by improving your air to fuel ratio. On average, drivers will see a 1-2mpg improvement.[1]
Disadvantages
- Hydrolock - The intake opening is lower to the ground than a standard air box, and more likely to introduce water into the engine when fording streams or flooded roads. Hydrolock generally does not occur unless the filter is fully submerged in water."Bypass filters" can be purchased which prevent most water from entering the engine. Some people use hydro shields to prevent this from occurring, however hydro shields are not completely water proof if the intake tube is completely submerged in water.
- Noise - Stock air filtration systems usually include resonator-based muffling tubes. Removing them reduces pumping losses but increases noise.
- Can void the engine warranty - Many auto manufacturers are denying warranty repairs of vehicles that have aftermarket engine modifications.
Application
Intake systems come in many different styles and can be constructed from plastic, metal, rubber (silicone) or composite materials (fiberglass, carbon fiber or Kevlar). The most efficient intake systems utilize an airbox which is sized to complement 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.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, those without a shroud to prevent engine bay heat ingestion are known as a "hot air intake". 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. Some systems called "fender mount" move the filter into the fender wall, this system draws air up through the fender wall which provides even more isolation and still cooler air.
Air bypass valves are gaining popularity in cold air intake manufacturing. An air bypass valve is a filtered spacer that is positioned more into the engine bay, between two connected pieces of the cold air intake assembly. This prevents hydro-locking by providing an alternate route for air to come in, thus eliminating the vacuum that causes water to be sucked in from a puddle. Foam filters are a simple piece of foam that is air permeable, and most have no valve. It is argued that this reduces power, but in actuality it provides more surface area for air to enter the engine when the driver accelerates. When driving at moderate speeds, the suction caused by the engine is not enough to activate the air bypass valve. Cloth filter bypass valves only allow air in if the valve is sucked open as result of the vacuum pressure caused by a blocked filter at the bottom of the intake.
[edit] See also
References
- ^ Cold Air Intake Advantages AutoAnything, Retrieved 2-3-2011
