Exhaust system of engine

An exhaust system for an engine comprising:

• an exhaust pipe connected to an exhaust port of the engine;
• and
• a muffler attached to a downstream end of the exhaust pipe and configured to reduce exhaust noise;
• said muffler including an inner cylinder part connected to the downstream end of the exhaust pipe, an outer cylinder part configured to cover an outside of the inner cylinder part, and noise absorbing material disposed between the inner cylinder part and the outer cylinder part;
• a plurality of first communication holes providing communication between an inside and the outside of the inner cylinder part, said plurality of first communication holes being formed in an upstream portion of the inner cylinder part;
• and
• a plurality of second communication holes providing communication between the inside and the outside of the inner cylinder part, said plurality of second communication holes being formed in a downstream portion of the inner cylinder part;
• wherein the plurality of first communication holes includes a guide wall extending toward the inside of the inner cylinder part and an inlet opening formed by the guide wall and opened toward an upstream side of exhaust,
• wherein the plurality of second communication holes includes a guide wall extending toward the outside of the inner cylinder part and an inlet opening formed by the guide wall and opened toward the upstream side of the exhaust, and
• wherein the plurality of first communication holes and the plurality of second communication holes are formed on the upstream side of the inner cylinder part rather than the downstream end thereof.