Air Filter Change

[Tractor Parts]

The inner and outer air filter separately serves its own functions. The outer filter stops the larger particles from entering the engine, and the inner filter stops the smaller dust/sand like materials. Its these dust/sand particles, much not visible to the naked eye, that has the potential to cause premature piston ring and cylinder damage. Its like running a piece of sand paper up and down the cylinder.

Usually air filters are changed on a time scale (e.g every 500 or 1000 hrs) or per milege of the machine. Provided that no excessive driving has been done, once per year at a minimum may suffice as a proper preventative maintenance schedule.
regards
M Khan
Ford Tractor Parts

 

[Mace Canute]

The following was taken from a study about the effect intake airfilter condition has on vehicle fuel economy
(See page 16)
"A factory OEM indicator was taken from a 2001 Chevrolet Silverado with 5.3L V8 and tested to find the
Outlet DP (pressure differential) required to set the indicator or move the yellow indicator into the red zone. Using a vacuum pump and water manometer to test the indicator, the authors determined that an Outlet
DP of about 5.7 kPa was needed to set the indicator to the level corresponding to a clogged air filter.
Other air filter indicators from diesel applications were also tested. Both of the other two air filter
indicators tested were factory equipment for Dodge Ram pickup trucks with 5.9L diesel engines. One was
purchased new from the Chrysler dealer and the other was taken from a 2006 Dodge Ram pickup
equipped with a 5.9L diesel engine. Using the same vacuum pump and water manometer, the authors found that the vacuum needed to set these indicators was slightly less than that required by the indicator
taken from the gasoline application. These air filter indicators only required about 4.2 kPa to move the
indicator to the level corresponding to a clogged air filter.
It is common for air filter service indicators to be set between about 5.0 and 7.0 kPa."

4.2 kPa = 0.609 psi = 16.861 inches of water column.
5.7 kPa = 0.827 psi = 22.883 inches of water column.
pressure-units-conversion calculator

There's some good information in that study related to air filters and restriction levels but the one thing we can get from it, at least, is what the car manufactures consider to be the maximum restriction that an air filter should have.

The study also says:
"It is common, however, for servicing to occur when the filter appears dirty. Engine air filters are designed to actually increase their efficiency by using this initial layer of dust as an added filter layer. Initial filter efficiency is usually approximately 98% but increases to more than 99% by the end of the service life of the filter. Therefore, changing an air filter before the useful service life is
achieved can result in premature engine wear."

This mirrors what others has often said- that a slightly dirty filter actually filters better than a brand new one.

 

[spruce Deere]

I once too wondered 'when' to change the air filter. I do it as needed. I have operated in total dust out conditions where I have had to stop to make sure I was still on coarse. Be it skidd'n logs with the 648 G-III, harrow'n or packing with the 790. In those conditions, outter filters get "knocked" clean daily and replaced after 40 hours of that harsh of service. Oil use has been a reliable indicator for me on air filter needs cleaned or time for new one after many cleanings. Small time window, or good weather you Gotta go, and go hard when you can.... Engine temp on the 648 is another indicator of air filter ailment too.

 

[ShenandoahJoe]

Just bought a new air filter for my Kubota. Now that I've seen how much they cost, I might have changed my opinion upwards a bit about the time between changes.