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Gasoline turbocharged direct injection (GTDI) engines, such as EcoBoost™ from Ford, are becoming established as a high value technology solution to improve passenger car and light truck fuel economy. Due to their high specific performance and excellent low-speed torque, improved fuel economy can be realized due to downsizing and downspeeding without sacrificing performance and driveability while meeting the most stringent future emissions standards with an inexpensive three-way catalyst. A logical and synergistic extension of the EcoBoost™ strategy is the use of E85 (approximately 85% ethanol and 15% gasoline) for knock mitigation. Direct injection of E85 is very effective in suppressing knock due to ethanol's high heat of vaporization - which increases the charge cooling benefit of direct injection - and inherently high octane rating. As a result, higher boost levels can be achieved while maintaining optimal combustion phasing giving high thermal efficiency.

In recent years, more attention has been focused on environment pollution and energy source issues. As a result, increasingly stringent fuel consumption and emission legislations have been implemented all over the world. For automakers, enhancing engine’s efficiency as a must contributes to lower vehicle fuel consumption. To reach this goal, Geely auto started the development of a 3-cylinder 1.0L turbocharged direct injection (TGDI) gasoline engine to achieve a challenging fuel economy target while maintaining fun-to-drive and NVH performance. Demanding development targets for performance (specific torque 205Nm/L and specific power 100kW/L) and excellent part-load BSFC were defined, which lead to a major challenge for the design of the combustion system. Considering air/fuel mixture, fuel wall impingement and even future potential for lean burn combustion, a symmetrical layout and a central position for the injector with 200bar injection pressure was determined.

In order to meet increasingly stringent emission regulations and reduce fuel consumption, development of modern powertrain is becoming more complicated, combining many advanced technologies. Gasoline engine downsizing is already established as a proven technology to reduce vehicle fleet CO2 emissions. Compressed natural gas (CNG) offers increased potential to further reduce both tailpipe CO2 and other regulated exhaust gas emissions without compromising driving performance. In this study, a turbocharged CNG port fuel injection (PFI) engine was developed based on gasoline version. Making most use of positive fuel properties of CNG, the paper quantifies the performance characteristics of downsized CNG engine considering reduced knock sensitivity, adaption of compression ratio and combustion efficiency. While peak cylinder pressure was controlled below 120 bar, peak torque 180Nm, same level as gasoline variant, was realized from 3000rpm.