Quantification of the Internal Surface Roughness of Cast Iron Exhaust Manifolds 2005-01-1625

A study has been conducted to quantify the typical internal surface roughness of a cast iron exhaust manifold. In addition, the range of surface roughness values that can be obtained with various manufacturing methods was measured. Initial investigations were conducted to measure the effect of a range of surface roughness values on the performance of the engine system, specifically torque and the thermal losses through the exhaust manifold walls. Several manifold geometries were used to represent a variety of actual manifold applications, including designs that were subjected to tight packaging constraints. Physical tests were used to show that large variations in surface roughness resulted in modest changes in manifold component pressure losses. A simulation tool was used to predict that modest improvements in manifold pressure losses have little impact on engine output.