Investigation on effect of exhaust manifold type and processing on gasoline engine performance

Exhaust manifold of a 1.5 L four cylinder gasoline engine was improved, the type 4-1 was replaced by type 4-2-1 and the forming technique was changed from casting to stamping-welding. The calculation results by using ANSYS FLUENT reveal that flow velocity uniformity coefficient of the new manifold reaches 0.910~0.935. Analysis by GT-POWER and actual engine test results show that the new manifold significantly improves engine torque characteristics, especially low speed torque increases by 5%. In addition, the exhaust manifold weight reduces up to 40%.