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To improve today’s 1D engine simulation techniques it is important to investigate how well complex geometries such as the manifold are modeled by these engine simulation tools and to identify the inaccuracies that can be attributed to the 1D assumption. Time resolved 1D and 3D calculations have been performed on the turbulent flow through the outer runners of an exhaust manifold of a 2 liter turbocharged SI engine passenger car The total pressure drop over the exhaust manifold, computed with the 1D and 3D approach, showed to differ over an exhaust pulse. This is so even though a pressure loss coefficient correction has been employed in the 1D model to account for 3D flow effects. The 3D flow in the two outer runners of the manifold shows the presence of secondary flow motion downstream of the first major curvature. The axial velocity profile downstream of the first turn loses its symmetry. As the flow enters the second curvature a swirling motion is formed.