Tuning Single Cylinder Two Stroke Engine Using Expansion Chamber

Abstract

Expansion chamber is an exhaust system used for power tuning in two strokes engines. The important of designing appropriate expansion chamber is for power tuning in two stroke engine to ensure the engine to produce more power output with a reduction of polluted emission as well. The two stroke engine does not utilize an exhaust stroke or complicated valve to emit the burnt gases from cylinder like four stroke engine. The incoming mixture charged is used to help push the burnt gases out of the exhaust port. This is not an efficient process since some of the burnt gases remained in the cylinder and may be some of the new mixture charge escaped through the open exhaust port. Thus expansion chamber enhances and control the flow through the engine by using pressure pulse. Two-stroke engines complete the process cycle in one crankshaft revolution: the
scavenging process takes place when the piston is close to the bottom dead center, with the opportunity to open and close the cylinder ports by means of the piston motion, greatly reducing the number of moving parts. This solution however, typically used in small engines, imposes a symmetrical timing with respect to the bottom dead center, leading to a lower scavenging efficiency than a four-stroke engine. Except for the short rpm range of dynamic tuning, two-stroke engines are affected by the short-circuit of fresh air-fuel mixture during the scavenging process: this phenomenon results in a fuel loss, subsequent lower torque and higher specific consumption, and also in an inevitable increase in pollutant emissions. Thus expansion chamber enhances and control the flow through the engine by using pressure pulse. The design of an expansion chamber will have an effect on the pressure movement. The design was based on different cross section and length, depending on the requirement of the type of engine. Expansion chamber will be design using empirical design process. By experimentation using ‘test dyno’, result obtained will be used to ensure better engine performance.