Effect of Intake Air Filter Condition on Vehicle Fuel Economy PDF Manual

A factory OEM indicator was taken from a 2001 Chevrolet Silverado with 5.3L V8 and tested to find the Outlet DP required to “set” the indicator or move the yellow indicator into the red zone (see Fig. 2.2). 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. Tests of diesel vehicles are planned as a follow-
on effort to the work reported here.

All of these functions are to be met for the service life of the filter without allowing engine performance 5 to be affected. In light- and medium-duty applications, the service life is normally defined by accumulated mileage. However, it is very common for over-servicing to occur in these applications due to 5,6 a lack of understanding of how optimum air filter efficiency is achieved. The standard recommended service life for an air filter in light- and medium-duty applications, during normal driving conditions, is 5–7 about 30,000 miles.

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
7,8 end of the service life of the filter. Therefore, changing an air filter before the useful service life is 6,9 achieved can result in premature engine wear.

In engineering terms, the service life of an air filter is commonly defined as a level of restriction which results in a pressure drop across the filter of approximately 2.5 kPa (10 in. water) more than the pressure 5,9–11 drop of the new or clean filter. Bugli and Green define this as the “final pressure drop” when conducting tests to investigate filter cleaning procedures: Wide-open throttle (WOT) tests were used to measure the changes in the filter pressure drop (Outlet DP). In a real-world application, the vacuum needed to set one of the air filter indicators would likely occur under heavy acceleration, such as merging onto an interstate, or climbing a steep grade.

Therefore the level of restriction was set, using an artificial clogging technique described below, to achieve the desired Outlet DP during a WOT acceleration from idle to approximately 85 mph or a steady-speed (SS) WOT test in which the dynamometer was held at a fixed speed, 65 mph, and the throttle was held open for 10 seconds. Using these test procedures, the 2007 Buick Lucerne was configured to achieve an Outlet DP
of approximately 7.0 kPa under the WOT acceleration and approximately 5.7 kPa under the SS WOT.

Once the method for achieving this restriction was developed, it was used with each vehicle. Using this approach, the V8-equipped Dodge Charger showed a slightly higher Outlet DP than the V6 Lucerne, and the I4 Camry showed a slightly lower Outlet DP. The 1972 V8 Pontiac was restricted in a similar manner and level. It is important to note that all the modern vehicles used rectangular cartridge style air filters (Figs. 2.3 and 2.4), while the 1972 Pontiac used the cylindrical filter element common in that era (Fig. 2.5).

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