Effective air filtration is one of the most important aspects of reducing engine wear. Dust particulates are extremely abrasive and when these particulates are not effectively stopped by the air filter, accelerated rates of engine wear can occur, or in extreme cases immediate internal engine damage can occur. Dust particles are classified into four major groups according to its particle diameter:
- “fine” dust with particles from 1 to 5 microns
- “medium” dust with particles from 5 to 10 microns
- “coarse” dust” with particles from 10 to 50 microns
- “sand” dust with particles from 50 to 250 microns.
To put this all in perspective, a grain of salt has a particle size of approximately 100 microns (0.1mm) and an average human hair has a particle size of approximately 90 microns (0.09mm).
They type and size of dust particulates present in the air depends on which area of the country or world you are in as well as the type of roads you are traveling on and the vehicles ahead of your vehicle which can kick up a lot more dust than normally present. It has been determined that dust particulates present in average air samples is composed of at least 70% silica. Automotive engines should be able to operate effectively in dust- polluted air up to a maximum concentration of 2.5 g/cu meter. Filters on assault tanks or tractors should be able to operate effectively during a long space of time at concentrations between 4 and 8 g/cu meter.
In the automotive testing business I am involved with some of the most severe engine dust ingestion testing is performed in Arizona using roads specially prepared with a specific particle size of Arizona test dust and dirt particulates and small pebbles and stones. A vehicle will drive ahead of the test vehicle dragging a special apparatus, which creates an extremely large cloud of dust that the test vehicle drives in. This test is used to evaluate many different parameters from engine wear, air filtration effectiveness, paint chip protection, stone pecking and functionality of underbody parts such as brake and fuel lines and many other parts.
Testing has indicated that piston rings and cylinders are more sensitive than other engine parts to dust ingestion. Maximum wear in the upper cylinder parts appears to occur with particles between 5 and 10 microns. This does not mean that it is not important to stop both smaller and larger dust particles. All sizes of dust particles commonly prevalent in the air on the roads we drive on have the potential to cause varying degrees of engine wear and must be stopped from passing through the air filter and entering the engine.
It is extremely important to make sure you that you use a quality air filter and that it is properly installed and sealed at the sides so that dust particles can get past unfiltered. The air filter must be able to both flow sufficient quantities of air for proper engine performance while also stopping damaging dirt and dust particles. A quality paper air filter is effective in stopping most of the dust particles; however there are superior filters on the market with will do a much better job.
My personal preference is an oiled foam air filter. The combination of the thick foam and the honeycomb network of oiled fibers are extremely effective in stopping damaging dust particles. The oil used is a special high tack type. Typically the filter requires cleaning and re-oiling about once per year or 25,000 miles, whichever comes first, or in cases where more dusty conditions are encountered, twice per year.
In SAE J726 air filter testing this type of oiled foam filter proved to be 99% efficient and could hold 281 grams of dust contaminant. To date, I have not seen any test results from other types of filters that could match this type of performance. A paper element could not come anywhere close to achieving this kind of efficiently and dust/dirt holding capacity nor could an oiled cotton gauze type filter. I have recently seen that certain cotton gauze type air filter manufacturers also offer a special oiled foam wrap or sock element to go over their air filter to act as a pre-filter and increase the dust/dirt stopping ability. If you have this type of filter, I highly recommend purchasing the foam or sock type pre-filter for additional dirt stopping ability.
