A warm air intake (WAI) also known as a hot air intake (HAI), is a

system A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpose and express ...

to decrease the amount of the

air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...

going into a car for the purpose of increasing the fuel economy of the

internal-combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combust ...

. This term is sometimes used erroneously to refer to a short ram air intake, which is another engine modification that aims to improve power output by increasing the static air pressure inside the intake manifold.

Operation

All warm air intakes operate on the principle of decreasing the amount of

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

available for

combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combus ...

with

fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy b ...

. Warm air from inside the engine bay is used opposed to air taken from the generally more restrictive stock intake. Warmer air is less dense, and thus contains less oxygen to burn fuel in. The car's ECU compensates by opening the throttle wider to admit more air. This, in turn, decreases the resistance the engine must overcome to suck air in. The net effect is for the engine to intake the same amount of oxygen (and thus burn the same amount of fuel, producing the same power) but with less pumping losses, allowing for a gain in fuel economy, at the expense of top-end power. Opposite principle of a cold air intake (CAI) which significantly differs by collecting air from a colder source outside the engine. In the extreme, a warm air intake can eliminate the need for a conventional throttle and thus eliminate throttle losses.Throttleless Premixed-Charge Engines, research project web page of Prof. Paul D. Ronney at Univ. of S. California. http://carambola.usc.edu/Research/TPCE/TPCE.html

References

{{Automotive engine , collapsed Engine technology

Operation

See also

References