Exhaust Gas Recirculation, Late Intake Valve Closure and High Compression Ratio for Fuel Economy Improvement in a MPI Gasoline Engine

The effects of exhaust gas recirculation (EGR), late intake valve closure (LIVC) and high compression ratio (HCR) on the performance of a 1.6L multi-point injection (MPI) gasoline engine at 2000rpmwere investigated in this paper. Compared to the baseline engine, The improvement of fuel consumption is about 1.4%∼4.5% by using EGR only because of a reduction of pumping loss(PMEP). Nevertheless deterioration of combustion is introduced at the same time for high specific heat of EGR. The maximum EGR rate introduced in this system is limited by cyclic variations of indicate mean effective pressure (COV_IMEP) at low load and fresh charge to achieve enough output power at high load. After combined LIVC and HCR, the improvement of fuel consumption is about 3.5%∼9.6% compared with the baseline engine at the same operation conditions because of significant PMEP reduction, increasing of effective compression ratio (ECR). LIVC&HCR&EGR can improve BSFC further, however, for getting stable combustion process and sufficient power, the combined technology is mainly suitable for medium load.