The present invention provides a four-stroke internal combustion engine (10) having reduced noise emissions. The engine includes a filter element (38,42) having substantially flat inlet and outlet sides, a first housing portion (30), and a second housing portion (34) coupled to the first housing portion. The first and second housing portions define an air chamber (74) in which the filter element is supported. The second housing portion (34) includes an interior surface, at least one protrusion (98) to space the inlet side of the filter element from the interior surface, and an air passageway (78). The outlet (86) of the air passageway (78) is positioned adjacent the interior surface to deliver air to the air chamber (74) between the interior surface and the inlet side of the filter element. A ratio of the volume of the air chamber (74) to the length of the air passageway (78) is between about 5 in 2 (32 cm 2 ) and about 20 in 2 (129 cm 2 ).

Title
Four-stroke internal combustion engine having reduced noise emissions
Application Number
200710100662
Publication Number
101033720
Application Date
February 15, 2007
Publication Date
September 12, 2007
Inventor
Zabrowski Geoffrey P
Whitmore Jeffrey H
Vissers Marvin
Rose Robert J
Matel Elliot
Kowis Kayne
Feist Jeffrey P
Disch Tom
Agent
caimin jun
Assignee
Briggs &Amp Stratton
IPC
F02M 35/02