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In this study the authority of the available engine controls are characterized as the high load limit of homogeneous charge compression ignition (HCCI) combustion is approached. A boosted single-cylinder research engine is used and is equipped with direct injection (DI) fueling, a laboratory air handling system, and a hydraulic valve actuation (HVA) valve train to enable negative valve overlap (NVO) breathing. Results presented include engine loads from 350 to 650 kPa IMEPnet and manifold pressure from 98 to 190 kPaa. It is found that in order to increase engine load to 650 kPa IMEPnet, it is necessary to increase manifold pressure and external EGR while reducing the NVO duration. While both are effective at controlling combustion phasing, NVO duration is found to be a "coarse" control while fuel injection timing is a "fine" control.

Intake boosting is an important method to improve fuel economy of internal combustion engines. Engines can be down-sized, down-speeded, and up-loaded to reduce friction losses, parasitic losses, and pumping losses, and operate at speed-load conditions that are thermodynamically more efficient. Low-temperature combustion engines (LTE) also benefit from down-sizing, down-speeding, and up-loading, but these engines exhibit very low exhaust enthalpy to drive conventional turbochargers. This paper describes modeling, evaluation, and selection of an efficient boost system for a 1.8L four-cylinder Gasoline Direct-Injection Compression-Ignition (GDCI) engine. After a preliminary concept selection phase the model was used to develop the boost system parameters to achieve full-load and part-load engine operation objectives.

Previous studies of gasoline direct-injection compression-ignition (GDCI) showed good potential for very high efficiency, low NOx, and low PM over the full speed-load range. Low-temperature combustion was achieved using multiple-late injection (MLI), intake boost, and cooled EGR. Advanced injection and valvetrain were key enablers. In the current study, a new piston was developed and matched with the injection system. Single-cylinder engine tests were conducted with the objective to reduce injection pressure, intake boost, and swirl levels. Results showed that ISFC could be further improved while maintaining low levels of NOx, PM, and combustion noise. Efficiency loss analysis indicated a very efficient thermodynamic process with greatly reduced heat losses. Injection parameters could be used to control combustion phasing with good combustion stability. Engine simulations were performed to develop a practical boost system for GDCI.

Global fuel economy and CO2 reduction mandates are driving the need for a substantial increase in vehicle fuel efficiency over the next several years, with improvements coming from many sources. This paper describes a vehicle demonstration program to improve fuel economy by implementing a systems approach to reduce friction and parasitic losses. The work concentrated on nearer term technologies that can be quickly transferred to production vehicle programs. Major technologies demonstrated on the vehicle included gasoline direct injection (GDi) with cooled EGR, advanced valvetrain, rollerization of both crankshaft and camshaft, and stop-start engine operation. The work described in this paper comprises Phase I of a two phase program funded by DOE contract DE-EE0003258. It includes a hardware overview and a description of the system development activities. Results focus on vehicle fuel economy benefits compared to a production baseline vehicle.