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A stoichiometric 2.0L turbocharged DISI engine is developed based upon the Theta 2.0L NA engine. The engine is intended to be installed in a midsize sedan as a downsizing concept, targeting to improve the fuel efficiency of the vehicles installed with the V6 3.3L engines while maintaining the performances. The base 2.0L engine is modified to accommodate the 4∼12MPa direct injection system with the multi-hole injectors and the intake/exhaust variable valve timing (VVT) system. The turbocharger is carefully matched so that the specific power over 85kW/L can be achieved while the maximum torque reached at 2000RPM. The fuel efficiency of the target vehicle was improved significantly due to the reduced friction and pumping losses compared to the vehicle equipped with the V6 3.3L engines. Various advanced gasoline turbocharger technologies for improving the transient performances are evaluated.

The influence of early induction stroke direct injection on late-cycle flows was investigated for a lean-burn, high-tumble, gasoline engine. The engine features side-mounted injection and was operated at a moderate load (8.5 bar brake mean effective pressure) and engine speed (2000 revolutions per minute) condition representative of a significant portion of the duty cycle for a hybridized powertrain system. Thermodynamic engine tests were used to evaluate cam phasing, injection schedule, and ignition timing such that an optimal balance of acceptable fuel economy, combustion stability, and engine-out nitrogen oxide (NOx) emissions was achieved. A single cylinder of the 4-cylinder thermodynamic engine was outfitted with an endoscope that enabled direct imaging of the spark discharge and early flame development.