ES300 — NEW FEATURES 13 2) 3-way Exhaust Control System A 3-way exhaust control system is used. This system reduces the back pressure by opening and closing two variable valves that are enclosed in the main muffler, thus varying the exhaust gas passage. The valves open steplessly in accordance with the operating condition of the engine, thus enabling a quieter operation at low to mid engine speeds, and reducing back pressure at high engine speeds. a. Operation i) Low Engine Speed Because the exhaust gas pressure in the main muffler is low, the 2 valves are closed. Chamber A serves as a resonance chamber, and a small- diameter bypass pipe provides a long-tail ef- fect.
Thus, exhaust noise is reduced by the muf- fler that has been designed with an emphasis on noise reduction. Small-Diameter Bypass Pipe Resonance Chamber Valves (Close) Exhaust Gas Chamber A 161ES06 ii) Mid Engine Speed When the exhaust gas pressure in the main muf- fler increases with the increase in engine speed, the valve of the bypass opens. By preventing the increase of pressure through the use of chamber A as an expansion chamber, the long-tail noise reduction effect of the small- diameter bypass pipe is maintained.
Valve (Open) Bypass Expansion Chamber Small-Diameter Bypass Pipe Valve (Close) Exhaust Gas Chamber A 161ES07 iii) High Engine Speed The valve of the outlet pipe also opens with the increase in the exhaust gas pressure in the main muffler. By opening the second valve by using chamber A as an expansion chamber, the flow passage area is secured, thus functioning as a low back pressure type muffler. Valve (Open) Expansion Chamber Outlet Pipe Exhaust Gas Chamber A Valve (Open) 161ES08