Study on exhaust system parameters for fuel economy improvement of small gasoline engine

Intake and exhaust systems are significant components of an internal combustion engine. The design and operational variables of intake and exhaust systems are decisive to determine overall engine performance. The best engine overall performance can be obtained by proper design of the engine intake and exhaust systems. The intake system parameters have been studied by numerous researchers. Therefore, this paper pays attention to the exhaust system parameters. The effects of exhaust pipe length and exhaust valve timing on the fuel economy performance of small gasoline engine are investigated based on thermodynamic cycle simulation. The simulation model of a small gasoline engine was constructed. Using the constructed model, engine work processes with different exhaust pipe lengths and different exhaust valve timings were numerically calculated. The calculation results demonstrate that the exhaust pipe length and exhaust valve timing exert great influences on the engine efficiency, mean pressure loss for gas exchange and indicated specific fuel consumption. The optimum exhaust system parameters for fuel economy are determined. The results provide theoretic guidance for the energy saving optimization of small gasoline engine.