Overview of Central-Injection Air-Assisted SIDI Technology Emissions and Fuel Consumption 2003-01-0545

The majority of first-generation Spark Ignition Direct Injection (SIDI) engines use Side-Injection, High Pressure Direct Injection (HPDI) combustion systems. Central-Injection is emerging as an alternative second-generation system. Side-Injection systems have an advantage in injector and spark plug packaging and cooling. Emission control systems are available for meeting current Japanese and European regulations. Central-Injection systems require the injector and spark plug to be closely spaced in the hotter and more crowded valve bridge area. This can pose potential development challenges with injector deposits and spark plug fouling. A potential benefit of Central-Injection is improved containment of the charge within the piston bowl, without wall guiding, resulting in lower emissions for future applications.

This paper presents results from three different engines used to assess Central-Injection as a second-generation SIDI technology. Specifically, a Spray Jet, Air Pressure-assisted DI (APDI) combustion system was used to compare with PFI and Side-Injection HPDI systems. The emission advantages of Central-Injection APDI, along with the fuel consumption, packaging and application issues, are discussed.