Abstract: In an air filter system for an internal combustion engine having a fresh air line with an air inlet, a filter housing with an upper housing half and lower housing half, a filter element disposed in the filter housing, a clean air outlet opening with an adjoining clean air line opening into the intake system of the internal combustion engine, and means for damping intake noise, the means for damping the intake noise is a sheet configured and arranged adjacent, and clamped to, the upper housing half opposite the clean air outlet whereby the intake noise vibration energy is absorbed by frictional relative movement between the sheet and the upper housing half, the intake noise being damped by a change in impedance, in particular by a jump in impedance.

Abstract: In an intake system for an internal combustion engine having an air filter with a fresh-air line opening into the fresh-air side of the air filter and a clean-air line leading from a clean-air side of the air filter to the internal combustion engine, an additional line which is in communication with the engine compartment extends into the fresh-air side of the air filter starting from the engine compartment, so as to be tapered in the direction toward the clean air side of the air filter with the inlet opening of the additional line being directed toward the adjacent passenger compartment.

Abstract: In an intake system for an internal combustion engine having a cylinder head with at least one inlet duct per cylinder, an essentially flat control flap is supported in the inlet duct on a pivot shaft pivotally about an axis which is disposed in spaced relationship upstream from the control flap by way of side support arms such that, in an open position, the control flap rests against a wall portion of the inlet duct from where it can be swiveled into the intake duct into a flow directing turbulence generating position.

Abstract: In an intake system for an internal combustion engine having a cylinder head with at least one inlet duct per cylinder, an essentially flat control flap is supported in the inlet duct on a pivot shaft pivotally about an axis which is disposed in spaced relationship upstream from the control flap by way of side support arms such that, in an open position, the control flap rests against a wall portion of the inlet duct from where it can be swiveled into the intake duct into a flow directing turbulence generating position.