Large Amplitude Wave Propagation in Exhaust Systems of Two-Stroke Engines

The characteristics of large amplitude wave propagation in variable area ducts were investigated in order to gain a more thorough understanding of exhaust systems for power tuned two-stroke engines. An apparatus to simulate the power stroke of a two-stroke motorcycle engine was developed, using a stock Yamaha 360 MX barrel, cylinder head, piston and ring. In this way, a single pulse of pressurized air could be introduced into virtually any duct geometry. An ocilloscope trace of the subsequent exhaust pulse and duct interaction was photographed. The resulting pressure-time histories were used to experimentally evaluate the effects of several duct terminations on the shape and timing of the reflected wave. The investigation resulted in quantifying the effects of an orifice plate and converging cone termination and in determining the best termination for a Yamaha 360 MX engine.