Internal combustion engine air filters:
The main application for air filters are combustion air to engines. The combustion air filter prevents abrasive particulate matter from entering the engine's cylinders, where it would cause mechanical wear and oil contamination.
Most vehicles and equipment use a pleated paper filter element in the form of a flat panel. This filter is usually placed inside a plastic box connected to the throttle body with duct work. Other equipment use a cylindrical air filter, usually between 100 millimetres (4 in) and 400 millimetres (16 in) in diameter. This is positioned above or beside the carburetor or throttle body, usually in a metal or plastic container which may incorporate ducting to provide cool and/or warm inlet air, and secured with a metal or plastic lid. The overall unit (filter and housing together) is called the air cleaner.
Air Filters by Equipment Brand
AC Delco
Allis Chalmers
Arctic Cat
Argo
Ariens
AYP / Electrolux
Bad Boy
Baja Motor Sports
Black & Decker
Bobcat
Bolens
Bombardier
Bosch
Bostitch
Briggs & Stratton
Campbell Hausfeld
Can-Am
Case
Caterpillar
Champion Power Equipment
Clark
Clinton
Club Car
Columbia
Comet
Craftsman
Cub Cadet
Cushman
Desa
Dewalt
Ditch Witch
Dixie Chopper
Dolmar
Dynamark
Earthquake
Echo
Emglo
Exmark
EZ-Go
Ferris
Ford
Fram
GEHL
Generac
Genie
Grasshopper
Gravely
Gutbrod
Hayter
Hilti
Hitachi
Homelite
Honda
Huskee
Husqvarna
Hustler
ICS
Ingersoll Rand
Ironton
Jacobsen
Jenny
JLG
John Deere
Jonsered
K&N
Kawasaki
Kohler
Kubota
Landpride
Lawn-Boy
Lawn Chief
LCT
Lesco
Lull
Makita
Mantis
Maruyama
Massey Ferguson
Mastercut
McCulloch
Motorcraft
MTD
Multiquip
New Holland
Northstar
Onan
Oregon
Partner
Pioneer
Polaris
Porter Cable
Poulan
Poulan Pro
Powerhorse
PowerMate (Formerly Coleman)
Raisman
Red Max
Remington
Ryobi
Sabo
Sanborn
Scag
Sears Craftsman
Shindaiwa
Simplicity
Ski-Doo
Skyjack
Snapper
Solo
Stiga
Stihl
Subaru / Robin
Suzuki
Tanaka
Tecnamotor
Tecumseh
Tomahawk
Toro
Troy-Bilt
Vermeer
Wacker
Walker
Weed Eater
White Outdoor
Wisconsin
Yamaha
Yanmar
Yard Machines
Yard-Man
Air Filter Types
Paper
Pleated paper filter elements are the nearly exclusive choice for automobile engine air cleaners, because they are efficient, easy to service, and cost-effective. The "paper" term is somewhat misleading, as the filter media are considerably different from papers used for writing or packaging, etc. There is a persistent belief among tuners, fomented by advertising for aftermarket non-paper replacement filters, that paper filters flow poorly and thus restrict engine performance. In fact, as long as a pleated-paper filter is sized appropriately for the airflow volumes encountered in a particular application, such filters present only trivial restriction to flow until the filter has become significantly clogged with dirt. Construction equipment engines also use this. The reason is that the paper is bent in zig-zag shape, and the total area of the paper is very large, in the range of 50 times of the air opening.
Foam
Oil-wetted polyurethane foam elements are used in some aftermarket replacement automobile air filters. Foam was in the past widely used in air cleaners on small engines on lawnmowers and other power equipment, but automotive-type paper filter elements have largely supplanted oil-wetted foam in these applications. Foam filters are still commonly used on air compressors for air tools up to 5 horsepower (3.7 kW). Depending on the grade and thickness of foam employed, an oil-wetted foam filter element can offer minimal airflow restriction or very high dirt capacity, the latter property making foam filters a popular choice in off-road rallying and other motorsport applications where high levels of dust will be encountered. Due to the way dust is captured on foam filters, large amounts may be trapped without measurable change in airflow restriction.
Cotton
Oiled cotton gauze is employed in a growing number of aftermarket automotive air filters marketed as high-performance items. In the past, cotton gauze saw limited use in original-equipment automotive air filters. However, since the introduction of the Abarth SS versions, the Fiat subsidiary supplies cotton gauze air filters as OE filters.
Stainless steel
Stainless steel mesh is another example of medium which allow more air to pass through. Stainless steel mesh comes with different mesh counts, offering different filtration standards. In an extreme modified engine lacking in space for a cone based air filter, some will opt to install a simple stainless steel mesh over the turbo to ensure no particles enter the engine via the turbo.
Oil bath
An oil bath air cleaner consists of a sump containing a pool of oil, and an insert which is filled with fiber, mesh, foam, or another coarse filter media. The cleaner removes particles by adhering them to the oil-soaked filter media rather than traditional filtration, the openings in the filter media are much larger than the particles that are to be filtered. When the cleaner is assembled, the media-containing body of the insert sits a short distance above the surface of the oil pool. The rim of the insert overlaps the rim of the sump. This arrangement forms a labyrinthine path through which the air must travel in a series of U-turns: up through the gap between the rims of the insert and the sump, down through the gap between the outer wall of the insert and the inner wall of the sump, and up through the filter media in the body of the insert. This U-turn takes the air at high velocity across the surface of the oil pool. Larger and heavier dust and dirt particles in the air cannot make the turn due to their inertia, so they fall into the oil and settle to the bottom of the base bowl. Lighter and smaller particles stick to the filtration media in the insert, which is wetted by oil droplets aspirated there into by normal airflow. The constant aspiration of oil onto the filter media slowly carries most of the finer trapped particles downward and the oil drips back into the reservoir where the particles accumulate.
Oil bath air cleaners were very widely used in automotive and small engine applications until the widespread industry adoption of the paper filter in the early 1960s. Such cleaners are still used in off-road equipment where very high levels of dust are encountered, for oil bath air cleaners can sequester a great deal of dirt relative to their overall size without loss of filtration efficiency or airflow. However, the liquid oil makes cleaning and servicing such air cleaners messy and inconvenient, they must be relatively large to avoid excessive restriction at high airflow rates, and they tend to increase exhaust emissions of unburned hydrocarbons due to oil aspiration when used on spark-ignition engines.
Water bath
In the early 20th century (about 1900 to 1930), water bath air cleaners were used in some applications (cars, trucks, tractors, and portable and stationary engines). They worked on roughly the same principles as oil bath air cleaners. For example, the original Fordson tractor had a water bath air cleaner. By the 1940s, oil bath designs had displaced water bath designs because of better filtering performance.