A filter housing (10) for a filter unit (50). The filter unit having a substantially semicylindrical air filter (52). The filter housing having an air inlet (20) and an engine air outlet (40). The filter housing has an extra air outlet (36) and an air aperture (64) to the extra air outlet (36). The air aperture extends between the filter unit (50) and the engine air outlet (40). The aperture (64) extends along a periphery of the engine air outlet. There is a filter unit for such a filter housing.