Experimental and quantitative analysis of influence of internal combustion engine exhaust manifold structure on engine performance

Since the development of internal combustion engines, rules of providing higher performance and better fuel economy have been remained same. The modern engines, meeting necessities of advanced vehicle performance, should also satisfy conditions regarding natural resources and environmental protection. One of the key issues considered during optimization studies is the decrease of losses. The resistance occurred due to air suction in the cylinder and discharged exhaust gases cause energy loss. In addition to structural form of manifold and air duct; shape, roughness, materials of internal surface and formation of laminar or turbulence airflow affects the resistance level. The purpose of this study is to increase engine performance by changing structure of manifold. The fuel/air mixture, exploded in the combustion chamber, discharges exhaust gases. The easier the discharge is, the better engine performs. Due to modified structure of exhaust manifold, the gas occurred in the combustion chamber could be discharged more easily and regularly. The discharged exhaust gases from each cylinder will be uniformed as a result of this structure. Within this process, pressure losses will be reduced; power increase would be achieved accordingly. In the numerical part of the study, pressure changes for same entry and exit border conditions in both exhaust manifolds are identified by Ansys Fluent v13 program. As a result of this study, higher pressure is observed in the original exhaust manifold compared to the modified exhaust manifold for the same border conditions. This observation proposes that exhaust counter pressure declines due to transformed geometry. In experiments, four-stroke cycle, four cylinders, spark- ignition and electronic fuel injection Toyota petrol engine has been used. Firstly, engine performance is analyzed by using the original exhaust manifold. Then, engine performance is analyzed by using the modified exhaust manifold. The results obtained in both tests were presented in comparative graphics. According to the test results, engine performance displays increases due to the modified exhaust manifold. Depending on the number of revolutions within the interval of 1800-4600 revolutions per minute, increases up to 8% in engine torque and shaft work have been achieved with the modified exhaust manifold.