Clean air intake is one of the most important conditions for optimal engine power, high torque, low fuel consumption and minimized pollutant emissions. With MAHLE air filters, up to 99.9 percent of dust, soot and tire wear particles are filtered out. At the same time, an optimal air/fuel mixture is assured. The high particle uptake capacity ensures long service life under extreme conditions such as heat, cold or chemical contaminants. Our quality filters prevent premature wear of valves, cylinder working surfaces, piston rings, bearings and other engine components. To ensure optimum filter performance, all filters should be replaced within the service intervals stipulated by the car manufacturers.

Filter seals - our air filters are completely sealed

Unfiltered air in the intake passage can contaminate the air flow mass sensor and distort the measuring results, cause malfunctions of the fuel injection and wear of the engine components. To prevent bypass air, our filters are form-fitted and the seals have been carefully selected.

PUR seals made from specially developed polyurethane (PU) foam ensure continuous sealing between dirty and clean sides. These seals are resistant to aging, chemical effects and are temperature stable. Their flexibility is designed to exactly fit the geometry of the sealing area.

Air filters for passenger cars

In the passenger car sector, round and panel elements are fitted in air filter housings mounted to the engine or chassis and are stabilized with glue beads at the dirty side and support grids at the clean side, depending on the specifications of the car manufacturer. For dust rich areas, an additional pre-cleaner in form of a foam mat is placed at the dirty side. For higher surface loads, metal or plastic support studs are used.

Air filters for commercial vehicles

In commercial vehicles, robust and at the same time low-weight air filter systems made from recyclable plastic are used that can also reduce air intake noises. In order to achieve a highly stable large filter surface, the filters are mostly cylindrical. To improve efficiency, radial sealing and axial supports are used. Additional safety inserts in the form of special non-woven cylinders protect the clean side of the filter element during maintenance and replacement.

The lungs of the engine

The first two decades of the automobile were marked by permanent engine failures—in particular, due to the high dust concentration on the unpaved roads in those days. The dirt particles reached the combustion chambers, where they caused severe abrasions of the piston rings, pistons and cylinder walls. This resulted in reduced engine power or even the dreaded piston seizures. Only when the so-called air cleaners were invented in the mid-30s, repair and service intervals of up to 4,000 km could be reached. The success story of the internal combustion engine is therefore hard to imagine without air filters. However, it has been a long journey from the first oil bath air filter of the 30s to the modern air intake modules of today.

A mesh of wires

In the first air filters, the filter element was a wire mesh enclosed by a metal housing. The working principle of the so-called “oil bath air filter“ was based on physical flows. The deflection of the air stream in the metal mesh produced a sieving effect that was utilized to separate the dirt. In order to collect the dirt the steel mesh was covered with engine oil. These filter elements had to be dismantled regularly, cleaned with cleaner's solvent and finally covered in oil again.

As engines became more and more efficient and fuel consumption decreased at the same time—the air requirement increased many times over. Filter elements made from wire mesh had now reached their limits, even when they were later combined with textile inserts.

In addition, filtration had to become finer and finer. There was also the demand to save weight and reduce size—and to cut back on servicing requirements in several respects. An oil filter needing extensive cleaning and problematic disposal did not meet the demands any longer: a new type of air filter system had to be developed.

Filters made of paper

When filter elements made of paper came on the market in 1953, they soon superseded the earlier metal mesh elements thanks to their far superior filter performance.

Only a short time later, in 1957, the Knecht Filterwerke (today: MAHLE Filtersysteme) developed a special kind of folding system for the filter paper and took out a patent under the trademark “MICRO-STAR“ for this system. This pleat system is still the standard in filter technology to this day.

The design of air filters has been adapted to meet the changing demands all the time. Initially, circular filter elements were used: a circular filter element is made from filter paper that is fixed with PUR foam. In order to separate dirt side and clean side at the pleat ends, these were sealed by a PUR end plate with sealing rib. This system of circular air filters is still used to this day.

Variable-length intake manifolds and complex intake systems

Already in the 90s, MAHLE developed so called variable-length intake manifolds in close cooperation with the automotive industry. On the one hand, this allows the engine to generate high torques even at low engine speeds and high peak power at high engine speeds on the other. A tumble flow that is generated deliberately in the combustion chamber (see text to the right) improves mixture formation and the combustion process. This results in reduced fuel consumption and exhaust emission.

Apart from air filtration, the complete intake systems used in modern engines with fuel injection systems have a number of additional tasks. Today's air filter housings often contain an airflow mass meter, a blow-by gas recirculation intake (see text to the right) as well as a service indicator and a heat shield that protects from direct thermal stress. Accordingly high are the demands on MAHLE as development partner and system supplier of the international automotive industry.

The three-stage resonance system

Another milestone in air intake module technology is the threestage resonance system developed by MAHLE, which can be controlled via two flaps integrated into the intake manifold. Resonance charging is effective over a wide speed range in three engine speed stages up to 7,000 rpm. The resonance system, which has been optimized and virtually verified with the aid of charge calculations, has already been used successfully in practice. MAHLE offers a range of products and developments that goes also here far beyond air filtration and includes control units for the resonance system and a crankcase ventilation system with oil mist separator, pressure control and feed line into the air intake module.