Search Results

Currently in Brazilian market we have application of two different fuels in large scale, gasoline with addition of 27% of hydrous ethanol, otherwise known as ethyl alcohol or alcohol and pure hydrous ethanol. These different fuels and their various blends combinations - from 27% (E27) to 100% (E100) of ethanol - make the gases from combustion have different physical characteristics, affecting directly the exhaust system acoustic performance. This study is going to describe the physical differences of the exhaust gases with various blends combination and their respective impact on the exhaust system acoustic performances.

Aiming to solve pass by noise issues, where the exhaust system is the main source, a bench test was built. It was based on an impedance tube method to measure the transmission loss of exhaust systems of vehicle combustion engines. The test bench reduces time on investigation of acoustic performance of exhausts systems and does not depend on weather conditions. The results were used to compare several proposals under investigation before assembling on the vehicle and also to give a comparable metric for validating numerical simulation modeling and analysis procedure. This paper describes the problems involved in the construction of the evaluation system. Three types of noise source were evaluated, considering pink and white noise.