Direct Injection Systems for Otto Engines 2007-01-1416
New challenges lie ahead for the gasoline engine, concerning the reduction of exhaust emissions and fuel consumption, as well as an improvement of driving dynamics. Gasoline direct injection is an enabling technology for gasoline engines to meet present and future challenges.
Homogeneous combustion processes are suitable for worldwide application, thanks to stoichiometric exhaust aftertreatment, and offer advantages concerning exhaust emissions during the catalytic converter light-off phase. The combination of turbocharging and direct injection enables high driving dynamics and, combined with engine downsizing, a fuel economy improvement of up to 15 percent. In order to meet the increased requirements in terms of linear flow range, solenoid valve injectors produced for European applications (starting in 1999) were further developed to feature an extended working flow range.
Spray-guided combustion processes with lean combustion offer the highest potential for reduced fuel consumption of gasoline engines, while at the same time providing high driving dynamics and low exhaust emissions. To exploit these potentials Siemens VDO developed a production-level injection system consisting of a piezo-electric injector, a high pressure pump with a maximum operating pressure of 20 MPa, and an engine control unit with dedicated power stages to drive the piezo actuator, running all the necessary control functions. The main component of the system is the injector. Thanks to its outward opening nozzle it enables a stable spray under all engine operating conditions, allowing a reliable ignition of the air/fuel mixture. Furthermore, the high dynamics of the piezo-electric actuator permit extremely quick switching times of the injector and the realization of multiple injections within one combustion stroke. This way very good combustion results are obtained, while at the same time the stratified speed and load operation range is significantly extended.