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May 27, 2014

Air filter technology

An examination of the components that keep vehicles running cleaner

by Bob Weber and Dan Pike

There’s more to a filter than meets the eye. The type of media used substantially affects the filter’s performance.
There’s more to a filter than meets the eye. The type of media used substantially affects the

To operate at peak efficiency, vehicles need clean filters to prevent contaminants from entering fuel, engine or air conditioning systems. Particles can cause poor performance and shorten the lifespan of the vehicle.

When these filters should be replaced depends on many factors, such as vehicle maker’s recommendations and the environment in which the filter operates. Therefore, routine inspection of the filters’ condition is crucial.

The following article on filters was compiled by Bob Weber, a contributing writer for our sister publication, Auto Service Professional, and written by Dan Pike, group executive, Filter Manufacturers Council (FMC) and vice president, membership and members services, Automotive Aftermarket Suppliers Association.

It’s time to clear the air about filters — those automotive components which keep your customers’ vehicles running clean. Here is a brief overview of motor vehicle filtration products, which include filters for the engine, oil, cabin air and transmission.

Filters: It’s what’s inside that counts

Any discussion of motor vehicle filters begins with filter media — the material inside the filter which captures dirt and foreign particles.

Filter manufacturers use many different types of media for various fluids and environmental extremes. The most common used filter media are cellulose-based and glass.

Cellulose media is manufactured with fibers of various sizes. On the top layer of the media, the fibers are fluffed up, rather than compacted down. When fluid and contaminants pass through the media, many particles collect on the fluffy fibers on the surface and don’t travel further into the filter.

Glass media was developed to be utilized in hydraulic systems because it has low flow restriction at high filtration efficiencies. These low-flow resistance properties are beneficial in hydraulics where cold oil is being forced through the media and when filtration in the 3 to 5 micron range is desired.

Glass media has a drawback regarding capacity. Typically, glass media has the same pore size and same fiber diameter through the entire sheet. The media can be manufactured to be very efficient, but then it is so tight that it has very little life or capacity.

Synthetic media is making inroads in replacement filters. In most lube, fuel and air filter applications, cellulose media remains the better choice. As with glass, the reason largely relates to capacity, or filter life. A brief description of the filtering process illustrates this. The process of fluids and contaminants collecting on the fluffy fibers of cellulose filter’s surface is called “adsorption.” The particles adhere to the surface fibers and don’t travel farther into the filter.

The more adsorption a media applies, the more small particles can be separated before they reach the small pore spaces on the screen side of the media. This keeps these small particles from plugging the media.

Cellulose media typically is thicker than synthetic. The thicker the media is, the more time the particles spend traveling through it.

Each time the fluid changes direction around a fiber, the momentum keeps particles traveling in the same direction they were going and they are driven into the fibers.

This particle separation is called “impingement.” As with adsorption, the more impingement that a media applies, the more particles are separated without plugging the tight pore space on the screen side.

Synthetic media does separate some particles with adsorption and impingement, but the smooth fibers can’t hold the particles in place. Often they are washed off with the fluid traveling through the media.

Synthetic media primarily uses the particle separation technique called “direct interception.” Direct interception is simply separating particles by passing the fluid through pore spaces that are small enough to catch them. However, once all pores are filled with the contaminant, the filter is plugged and its life is over.

Because cellulose media is better at adsorption and impingement, it can remove more contaminants than glass or synthetic media without plugging pore spaces.

Can a synthetic media be created with the benefits of cellulose media? This remains to be seen. For now, both cellulose-based media and glass media have a place in today’s filter market.

Keep your customer’s car running clean: Oil filters

Of all the many filters on their vehicles, car owners are most familiar with the oil filter. To become your customer’s valued partner in keeping his or her vehicle in top condition, it’s important that you educate them on the importance of regular oil and filter changes.

You probably will encounter some common questions from your customers regarding their cars’ filters. The most common among new car owners is likely to involve the car’s warranty.

Many consumers mistakenly believe that installing an aftermarket filter on their new car will void its warranty.

 This is your opportunity to inform your customers about their right to have their vehicle serviced at the repair facility of their choice and about the federal laws, such as the Magnuson-Moss Warranty Act, which protect their right to choose. (You can learn more from the FMC Technical Service Bulletin 85-1R2.)

Another common question is about the quality of aftermarket filters, and whether they are as good as original equipment (OE) filters. You can assure your customers the full service manufacturers who make name brand, quality replacement filters design and manufacture their products to meet or exceed the requirements for OE filters. The use of an aftermarket filter will not affect the service intervals recommended by the carmaker.

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