The Effect of Geometry on Stiffness and Deformation in Exhaust Manifolds for In-line 4-cylinder Engines

Investigations were conducted on a quasi quantitative analysis method for exhaust manifold stiffness and deformation that is useful when designing exhaust manifolds for in-line 4-cylinder engines. This method analyzes the exhaust manifold as a combination of beams, making it possible to obtain the effects of the dimensions and shapes of major parts of exhaust manifold on stiffness and deformation. These results clarified the effects of various exhaust manifold shape characteristics (aspect ratio, branch ratio, offset ratio) on non-dimensional stiffness, and also the effects of aspect ratio on the non-dimensional warping quantity. In addition, the effects of each of the aspect ratio, collective part different angle, branch ratio and offset ratio on non-dimensional stiffness and deformation when the dimensions and shape of each exhaust manifold part are changed could also be clarified by obtaining the degree of effects of each factor. The proposed method is effective for determining and investigating the validity of major approximate dimensions, particularly when designing new exhaust manifolds with limited outer dimensions. Exhaust manifolds can be efficiently developed by performing CAE calculations on exhaust manifold shapes that have been determined using this method.