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The main goal of the research was to redesign the exhaust line of a Y61 code motored Nissan Patrol in a way that would result in a better throttle response of the engine without replacing the existing turbocharger with a newer design. To achieve this target, enthalpy of exhaust gases entering the turbine had to be increased while cylinder backpressure had to be reduced. To increase exhaust gas enthalpy, exchanged energy between hot gases and the surrounding of the exhaust manifold had to be reduced, while cylinder backpressure was reduced using a 4 in 2 in 1 design of the exhaust manifold. This arrangement takes advantage of greater distance between two consecutive firing, connecting first cylinders one with four, two with three, and then the two resulting gas flows, thus instead of 180 °CA the distance between two consecutive firing being 360 °CA.

Both designs (standard and optimized) were modeled in AVL BOOST software and simulations were run to show the benefit of the optimized version.

With the optimized design the torque curve of the engine was optimized, having a greater slope of the torque gradient over the 1500-2000 rpm bandwidth, thus improving the time to torque characteristics of the engine.

The novelty of the paper consists of the combination of the two design approaches applied to the exhaust line of the engine to achieve the proposed performance gains.