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Variable valve actuation is a focus to improve fuel efficiency for passenger car engines. Various means to implement early and late intake valve closing (E/LIVC) at lower load operating conditions is investigated. The study uses GT Power to simulate on E/LIVC on a 2.5 L gasoline engine, in-line four cylinder, four valve per cylinder engine to evaluate different ways to achieve Atkinson cycle performance. EIVC and LIVC are proven methods to reduce the compression-to-expansion ratio of the engine at part load and medium load operation. Among the LIVC strategies, two non-traditional intake valve lift profiles are investigated to understand their impact on reduction of fuel consumption at low engine loads. Both the non-traditional lift profiles retain the same maximum lift as a normal intake valve profile (Otto-cycle) unlike a traditional LIVC profile (Atkinson cycle) which needs higher maximum lift.

Several diesel passenger car boosting systems were studied to assess their impact on vehicle performance and fuel economy. A baseline 1.5L diesel engine model with a single VGT turbocharger was obtained through Gamma Technologies' fast running model library. This model was modified to explore multiple two stage boosting systems to represent the anticipated architecture of future engines. A series sequential turbocharged configuration and a series turbocharger-supercharger configuration were evaluated. The torque curves were increased from that of the original engine model to take advantage of the increased performance offered by two stage boosting. The peak cylinder pressure for all models was limited to 180 bar. Drive cycle analysis over the WLTP was performed using these engine architectures, while assessing the sensitivity to various system parameters. These parameters include: vehicle weight and aerodynamic drag, EGR target maps, level of downspeeding, and turbocharger inertia.

An advanced Variable Valve Actuation (VVA) system is optimized for response time in order to provide robust switching at high engine speeds. The VVA system considered is Cylinder Deactivation (CDA) for the purpose of improving fuel economy. Specifically, a Switching Roller Finger Follower (SRFF) on a Dual Overhead Camshaft (DOHC) engine is optimized for cylinder deactivation. The objective of this work is to (1) improve the latch response time when the system response is the slowest, and (2) balance the “ON” and “OFF” response time. A proper tradeoff was established to provide the minimum switching time such that deactivation and reactivation occurs seamlessly and in the right sequence. The response time optimization is accomplished while maintaining the existing packaging space of the overhead. A camshaft with a single lobe per SRFF device on a type II valvetrain was used as the baseline configuration for this study.