Warm air intake
Encyclopedia
For other uses, see Warm air intake (disambiguation)
.
A heated air inlet or warm air intake is a system commonly used on the original air cleaner assemblies of carburetted
engines to increase the temperature of the air going into the engine for the purpose of increasing the consistency of mixing of the air and fuel in order to reduce engine emissions
and fuel usage.
The system was often used with computerised carburettors or throttle body injection systems but is typically not used with multi-point fuel injection, as the problem of fuel falling out of suspension does not occur when the fuel injectors are located close to the inlet valves.
There are exceptions to this however. Some vehicles, such as the 1992 and 1993 Fox body Mustangs, do use such as a system even though they have multi-port fuel injection, presumably to help the air-fuel mixture burn at the proper rate in cold weather, as even though the fuel has finely atomized, it has not properly vaporized, and therefore flame propagation will be otherwise slower. These vehicles have a MAF sensor, Air Temperature sensor, and when equipt with the 2.3L 4-cylinder two spark-plugs per cylinder. This combination ensures the air is just warm enough to vaporise the droplets and does very noticeably improve performance and emissions at the same time in cold, northern winter weather.
that do not change state to vapour under the temperature and pressure conditions present in the intake system of an engine.
Fuels such as liquefied petroleum gas
and natural gas
do not require this heating, as they are in gaseous form in the intake, mix more effectively with the air and cannot fall out of suspension.
of the inlet air and fuel, it has the disadvantage of reducing air density, which reduces the volumetric efficiency
of the engine. The installation of a heated air intake system is hence beneficial to engine emissions but decreases maximum available power.
s, making the vehicle illegal.
Warm air intake (disambiguation)
warm air intake may refer to:* An air intake of an internal combustion engine which draws air from inside the warm engine bay.* Heated air inlet of carburetted engines to increase the temperature of the air going into the engine for the purpose of increasing the consistency of mixing of the air and...
.
A heated air inlet or warm air intake is a system commonly used on the original air cleaner assemblies of carburetted
Carburetor
A carburetor , carburettor, or carburetter is a device that blends air and fuel for an internal combustion engine. It is sometimes shortened to carb in North America and the United Kingdom....
engines to increase the temperature of the air going into the engine for the purpose of increasing the consistency of mixing of the air and fuel in order to reduce engine emissions
Automobile emissions control
Vehicle emissions control is the study and practice of reducing the motor vehicle emissions -- emissions produced by motor vehicles, especially internal combustion engines....
and fuel usage.
Operating principle
Heated air intake systems operate on the principle of increasing the temperature of the air such that when the air and fuel mix in the carburettor, the fuel will more effectively stay in suspension in the air rather than falling out of suspension and forming droplets on the floor of the manifold. Warm air from the outside of an exhaust manifold is drawn up into the air cleaner to increase the air temperature as quickly as possible after the engine starts. The air cleaner assembly incorporates a thermostatic vacuum switch that responds to the air temperature after the air filter element and actuates a vacuum motor that moves the control flap to allow the air to be drawn from a cooler location such as the top of the engine bay or outside the engine bay. If the air becomes too cold, the thermostatic switch will automatically change back to drawing heated air from around the outside of the exhaust.The system was often used with computerised carburettors or throttle body injection systems but is typically not used with multi-point fuel injection, as the problem of fuel falling out of suspension does not occur when the fuel injectors are located close to the inlet valves.
There are exceptions to this however. Some vehicles, such as the 1992 and 1993 Fox body Mustangs, do use such as a system even though they have multi-port fuel injection, presumably to help the air-fuel mixture burn at the proper rate in cold weather, as even though the fuel has finely atomized, it has not properly vaporized, and therefore flame propagation will be otherwise slower. These vehicles have a MAF sensor, Air Temperature sensor, and when equipt with the 2.3L 4-cylinder two spark-plugs per cylinder. This combination ensures the air is just warm enough to vaporise the droplets and does very noticeably improve performance and emissions at the same time in cold, northern winter weather.
Fuels
Heating of the intake air is specifically used for liquid fuels such as petrolGasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
that do not change state to vapour under the temperature and pressure conditions present in the intake system of an engine.
Fuels such as liquefied petroleum gas
Autogas
Autogas is the common name for liquefied petroleum gas when it is used as a fuel in internal combustion engines in vehicles as well as in stationary applications such as generators. It is a mixture of propane and butane....
and natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
do not require this heating, as they are in gaseous form in the intake, mix more effectively with the air and cannot fall out of suspension.
Disadvantages
While heating the inlet air provides a benefit by improving homogeneityHomogenization (chemistry)
Homogenization or homogenisation is any of several processes used to make a chemical mixture the same throughout.-Definition:Homogenization is intensive blending of mutually related substances or groups of mutually related substances to form a constant of different insoluble phases to obtain a...
of the inlet air and fuel, it has the disadvantage of reducing air density, which reduces the volumetric efficiency
Volumetric efficiency
Volumetric efficiency in internal combustion engine design refers to the efficiency with which the engine can move the charge into and out of the cylinders. More specifically, volumetric efficiency is a ratio of what quantity of fuel and air actually enters the cylinder during induction to the...
of the engine. The installation of a heated air intake system is hence beneficial to engine emissions but decreases maximum available power.
Removal
Where heated air intake air cleaner assemblies are fitted to engines, it is a common perception that they reduce maximum engine power and it is consequently common for them to be removed and a more open air cleaner assembly fitted in their place. This has the benefit of a marginal increase in power with the disadvantage of significantly increased emissions and, in some jurisdictionJurisdiction
Jurisdiction is the practical authority granted to a formally constituted legal body or to a political leader to deal with and make pronouncements on legal matters and, by implication, to administer justice within a defined area of responsibility...
s, making the vehicle illegal.