Impact on Performance, Emissions and Thermal Behavior of a New Integrated Exhaust Manifold Cylinder Head Euro 6 Diesel Engine

The integration of the exhaust manifold in the engine cylinder head has received considerable attention in recent years for automotive gasoline engines, due to the proven benefits in: engine weight diminution, cost saving, reduced power enrichment, quicker engine and aftertreatment warm-up, improved packaging and simplification of the turbocharger installation. This design practice is still largely unknown in diesel engines because of the greater difficulties, caused by the more complex cylinder head layout, and the expected lower benefits, due to the absence of high-load enrichment. However, the need for improved engine thermomanagement and a quicker catalytic converter warm-up in efficient Euro 6 diesel engines is posing new challenges that an integrated exhaust manifold architecture could effectively address. A recently developed General Motors 1.6L Euro 6 diesel engine has been modified so that the intake and exhaust manifolds are integrated in the cylinder head. Extensive CAD/CAE/CAM analyses have been employed in order to guide the design of the overall surface and the water cooling jacket that surround the exhaust manifold of the new engine version, and thus to be able to improve the low-frequency thermal fatigue resistance of the head. The thus obtained prototype engine head has been tested on a highly-dynamic test bench at the Politecnico di Torino in order to characterize performance, emissions and thermal behavior in comparison to the baseline production engine. The results have generally been very promising and have shown the possibility of maintaining the same performance rating over the overall engine speed range as well as comparable emissions and brake specific fuel consumption in steady-state conditions. Furthermore, appreciably faster engine and aftertreatment warm-up have been recorded due to the higher heat fraction that is transferred to the coolant and to the more favorable exhaust gas enthalpy management. The latter benefit is in fact very interesting as far as the control of HC and CO emissions within the NEDC homologation is concerned