(57) An exhaust manifold for a four-cylinder internal combustion engine, including four
branches (5,6,7,8), a downstream exhaust pipe (9) connected with the four branches,
and a partition wall (10,110) dividing an exhaust path in the downstream exhaust pipe
(9) into first and second passages (11,12) each having a semicircular section. Each
of the first and second passages (11,12) is connected with two of the branches (5,6,7,8)
which are connected with two of the four engine cylinders (#1,#2,#3,#4) having non-continuous
order of ignition and communicated with first and second quarter-circular regions
(A,B,C,D) in the semicircular section of the passages (11,12), respectively. An air-fuel
ratio sensor (16) mounted to the downstream exhaust pipe (9) projects into both of
the passages (11,12) through a cutout (18) formed on one side of the partition wall
(10,110) in a width direction perpendicular to an axial direction of the downstream
exhaust pipe (9). A communication portion (21,22,23,24) formed in the partition wall
(10,110) fluidly communicates the passages (11,12) with each other.
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