The automotive industry is facing tremendous challenges to improve fuel economy and emissions of the internal combustion engine. In the US, 2025 standards for fuel economy and CO2 emissions are extremely stringent. Simultaneously, vehicles must comply with new US Tier 3 emissions standards. In all market segments, there is a need for very clean and efficient engines operating on gasoline fuels.
Gasoline Direct Injection Compression Ignition (GDCI) has been under development for several years and significant progress has been realized. As part of two US DOE programs, Delphi has developed a third generation GDCI engine that utilizes partially premixed compression ignition. The engine features an innovative “wetless”, low-temperature, combustion system with the latest high-pressure GDi injection system. The system was developed using extensive simulation and engine testing. The powertrain features advanced boost, thermal management, EGR, and aftertreatment systems that meet packaging requirements for a D-class passenger car. Key program objectives include diesel-like fuel efficiency, extremely low tailpipe emissions on-cycle and off-cycle, and robust GDCI combustion with good transient control. The engine is compatible with a range of gasoline fuels including less-processed, low-octane gasoline and higher-octane, high-sensitivity gasoline.
Preliminary test results using RON91 fuel indicated very low fuel consumption, while meeting targets for engine out NOx and PM emissions, combustion noise and stability. BSFC at the 2000 rpm-2 bar BMEP global test point was 250 g/kWh. Minimum BSFC was measured at 205 g/kWh with inert catalysts over a wide range of medium loads where customers regularly drive. The aftertreatment system exhibited high exhaust temperatures and high conversion efficiency for HC and CO emissions. Preliminary tests at cold cranking conditions indicated robust first-cycle combustion with the potential for fast catalyst light-off. The paper reviews the latest system developments to achieve a practical, commercially-feasible GDCI powertrain.