MAHLE air filters: clean air, high performance

Many major automobile and engine manufacturers rely on the expertise of MAHLE for air filters—for good reason: engine performance, torque, low consumption, and minimal emissions require well-filtered air. And our cellulose (paper) filters, plastic non-wovens, or a combination of both can trap just about everything. They capture up to 99.98% of toxic dust, soot, and tyre particles. The finest filters trap nearly all particles larger than 3 µm. This means that MAHLE air filters prevent premature wear of valves, cylinder surfaces, piston rings, bearings, and other engine components. But be careful: in order for the filters to work perfectly, they must be replaced at the intervals prescribed by the automobile manufacturer.

In order to protect the filters from moisture, the intake port is designed to keep water away from the filter element as much as possible. If moisture does reach the filter anyway, we have added another layer of protection. Our filter papers are impregnated with a special synthetic resin that increases the resistance of the filter insert to water and chemicals. Glue beads on the backs of the folds help the filter elements retain their shape.

The demands on our air filters are pretty tough

Air filters must function reliably even under extreme conditions. For high loads in dusty regions, a prefilter is used—a foam mat and metal or plastic mesh providing support on the downstream side. In particularly damp areas, prefilters with additional water-repellent non-woven overlays can help.


Air filters with metal mesh providing support on the downstream side

In addition to filtering the air, air filters also need to reduce intake noise. Robust, weight-optimised air filter systems made of recyclable plastic are used in commercial vehicles. They are often cylindrical and have radial seals and axial supports.

Package is becoming ever smaller, thus resulting in the use of flat shapes. A special non-woven mat protects the clean side of the filter during maintenance and replacement.

MAHLE filter papers are pleated in order to create more surface area for capturing dirt in a small space. If the pleats are not strong enough then pleat deformation can occur. The differential pressure squeezes them together so tightly that little to no air can flow through the filter. This causes poor filtration, reduces the service life of the filter, and increases fuel consumption and pollutant emissions. The pleats in passenger car filters are therefore often reinforced with glue beads.

Materials: for the safety of people, engines, and the environment—only the best

The cellulose is first impregnated with special resins in a complex process. This increases the stability of the pleats and prevents deformation. Then they are preheated, which prepares the paper for the forming process, known as embossing. Then the paper is pleated to meet requirements. The impregnation then needs to cure in order to give the paper mechanical strength as well as chemical and thermal resistance.

Filter mats are made from plastic fibres with thicknesses in the µm range: the finer the fibre, the better the filtration. These mats are designed in layers, and the density and fineness of the fibres increase from the dirty to the clean side. Known as the funnel effect, this allows a very high dirt-holding rate with low flow resistance.

Multilayer filter media combine non-woven and paper. Their production is complex, but in comparison with conventional paper filters they hold over 40 per cent more dirt with comparable separation efficiency.

Research and development for the repair shop: so that you can continue to install safe products in the future

Organic development: bioplastics

In addition to air filters made of cellulose and conventional plastics, MAHLE has developed a filter system made of bioplastics that is ready for series production. The environmentally friendly product made of renewable raw materials also has three practical advantages: an especially smooth surface reduces turbulence, the weight is up to 25% lower than a conventional filters, and assembly is easier owing to the material’s flexibility.

Cool development: cascaded intercooling

As boost pressure increases, it becomes more and more important to cool the compressed, heated air. This is because more heat means less power output. MAHLE and MAHLE Behr have therefore developed a cascaded intercooling system integrated in the intake pipe, in which two coolant circuits are configured sequentially. The system first cools the charge air through the engine’s high-temperature coolant circuit; the cooled air then goes through a low-temperature circuit. This has several advantages:

  • Cooling performance is very high; charge air is thus cooled down nearly to the low temperature of the coolant.
  • The pressure drop is up to 80 per cent lower than for direct intercooling.
  • Large charge air pipes can be replaced with much thinner coolant lines.
  • The complete package is also much simpler in design.

In petrol engines the new intercooling system reduces consumption under full load by up to five per cent. At partial load, the system is characterised by lower emissions and better overall responsiveness. With this new technology, MAHLE has demonstrated noticeable consumption improvements in diesel engines under full load.

Prototype of the MAHLE air intake module with integrated cascaded intercooling for diesel engines

OE-compliant development: filters with special gaskets

Of course, all MAHLE and Knecht air filters fulfil the tough requirements of automobile, motorcycle, and engine manufacturers. The separation level, dust retention, and service life are specifically defined, even under extreme temperatures or high levels of water. Production quality is identical from the first filter to the last.

This is also important, as contaminated air can cause problems with the injection system and wear on engine components. But our precision-fit filter sets guarantee seamless sealing between the dirty and clean sides. The PUR gaskets, made from a specially developed polyurethane foam, have a precisely defined flexibility so they can optimally adapt to the sealing geometry. They are also resistant to temperature, chemical influences, and ageing.

Innovative: the horseshoe air filter with patented production technology

MAHLE engineers developed an entirely new air filter shape for the extremely tight conditions in the Mercedes C- and E-class engine bay. The horseshoe filter minimizes head room, is extremely strong, low-noise, and allows long service life. It also helps to protect pedestrians in case of an accident. Should you be interested, we would be happy to provide information about this and other MAHLE innovations.

Horseshoe filter: pressure gradient from intake (red) to clean air outlet (blue).