Abstract: A panel-type filter employs a rectangular filter element having shifted pleats wherein the peaks of the pleats on the upstream and downstream sides of the filter medium alternate between high and low peaks. By so configuring the filter medium, turbulence is decreased at the upstream side of the filter which reduces restriction. The reduced restriction increases air flow to the engine which results in reduced fuel consumption and higher engine output power. Moreover, compression and turbulence is reduced at the downstream side of the filter resulting in flow past sensors to the engine which is more laminar, thus increasing the effectiveness of the sensors.

Abstract: Air filter elements with primary filter medias have foam pre-cleaners with an increased surface area provided by an upstream face which has peaks and valleys. In one embodiment, the peaks and valleys are defined by parallel ribs. If the filter element is a panel-type filter element having a pleated primary filter media, then, in accordance with one embodiment, the pre-cleaner is secured to the primary filter media by adhesive deposits on the peaks of the primary filter media. If the filter element is annular, the pre-cleaner is also annular and is slid axially over a perforated sleeve or screen on the primary filter media and held thereon by friction. By having the upstream surface of the foam pre-cleaner configured in peaks and valleys, the surface area of the upstream surface is increased substantially, which improves the capacity, efficiency and life of the filter element.