F7     F9




Air Filter (Paper)


This type of air filter is very popular amongst some, mostly young people, hopefully always also with the necessary registration approval. It does what the normal air filters try, at all costs, to avoid. By having a different pore-size, it less effectively isolates the engine noise and probably allows the intake air to pass more freely. Higher engine wear and tear is the result. In normal operation, an air filter should seal to the casing completely, and not allow unfiltered air into the engine. The air-flow suction damping quality of the air filter is very often underestimated. Without filter the suction noises are heard substantially louder, and also some of the mechanical engine noises.

Clogged air filters increase fuel consumption.


Apart from the properly designed rubber sealing, the choice of filter paper is important for filter manufacturers. The pore size must concur precisely with the particle size (approx. 4-6 thousandth of a millimetre) permitted by the manufacturers. Nowadays, further in the course of the inlet manifold, there are air-volume meters in petrol and in diesel engines which react very sensitively to dirt deposits. Measurement errors and a permanent coating can be the results.
All in all, high demands are made on the filter paper. It must form precise and stable pleats, and the size of the surface area, when changing filter elements, should correspond to that of the original. It should be effeciently impregnated so that its form and function, also in humid conditions, are maintained. 10/09