Exhaust manifold

An exhaust manifold comprising:

• an inlet portion that collects exhaust gas discharged through a first exhaust port, a second exhaust port, a third exhaust port, and a fourth exhaust port after combustion of an engine;
• an outlet portion discharging the exhaust gas collected by the inlet portion;
• and
• a tube portion connecting the inlet portion and the outlet portion;
• wherein the inlet portion includes:
• a first inlet portion having a first end that communicates respectively with the first and the second exhaust ports;
• and
• a second inlet portion having a first end that communicates respectively with the third and the fourth exhaust ports,
• wherein the first and the second exhaust ports are not adjacent in an engine combustion sequence but are adjacent in a disposition sequence, and the third and the fourth exhaust ports are not adjacent in an engine combustion sequence but are adjacent in a disposition sequence;
• wherein the tube portion includes a first tube having an end that is connected to a second end of the first inlet portion, and a second tube having an end that is connected to a second end of the second inlet portion;
• wherein the first inlet portion and the second inlet portion respectively include portions having a width that becomes narrower in a direction going toward the tube portion, and the first and the second tubes have the same diameter along whole lengths thereof respectively;
• and
• wherein the diameters of the first and the second tubes have sizes corresponding to minimum widths of the first and the second inlet portions respectively.