Influence of intake pipe length and diameter on the performance of a spark ignition engine

This work shows the influence of intake pipe length and diameter on the performance of a spark ignition engine. A production four-stroke, four-cylinder, eight-valve, 1.0-l engine was tested in a bench dynamometer, fuelled by a blend of 78 % gasoline and 22 % ethanol. Experiments were carried out in the engine speed range from 1,500 to 6,500 rev/min. Three intake pipe lengths-0.3, 0.6 and 0.9 m-and three intake pipe diameters-0.044, 0.053 and 0.067 m-were investigated. The effects of intake pipe geometry on intake air mass flow rate and volumetric efficiency and the impacts on engine performance parameters-torque, power, thermal efficiency and specific fuel consumption-were evaluated. The results revealed that, for low engine speeds, the intake pipe with longer length and smaller diameter produced the best performance. On the other hand, the intake pipe with shorter length and larger diameter delivered the best engine performance at high speeds.