Compliance with future emissions standards such as Euro 6b (from 9/2014) and Euro 6c (from 9/2017) will call for further improvements in engine combustion processes. As gasoline engines offer significant scope for reducing emissions through more efficient combustion, downsizing and turbocharging, they will play a significant part in realizing these improvements.
This explains the ongoing worldwide trend of bringing increasing numbers of gasoline direct-injection engines onto the market. The high-performance injectors required for this highly efficient type of engine are currently designed to operate at pressures up to 200 bar. International automotive supplier Continental was quick to develop a solution that meets the needs of such applications, in the shape of the XL3 solenoid injector which went into volume production this year in a new turbocharged 1.5-litre GDI engine. “The debut of the XL3 injector in a compact 4-cylinder gasoline engine is further proof of the potential of our injection technology,” says Wolfgang Breuer, Head of the Engine Systems Business Unit in Continental’s Powertrain Division.
“Building on the level we’ve already reached, we are continuing to work on the XL3 injector with an eye to meeting the stringent requirements of Euro 6c,” adds Breuer. The refinements will focus among other things on designing the actuation system for fast injector opening and closing, which is key to ensuring ultra-accurate metering performance, particularly in the small quantity range. “Precision metering, combined with multiple injection capability, helps to reduce the particulate emissions of GDI engines and can cut the costs of aftertreatment technology,” says Breuer.
Matching the injector to the engine
For maximum fuel efficiency, GDI engines require extremely precise matching of the injector characteristics to the engine. “The XL3 injector has the precision it takes to meet this requirement,” says Gunnar Lowack, Head of the Injector Product Line in the Powertrain Division’s Engine Systems Business Unit. “For example, the Controlled Solenoid Injection (COSI) function continuously monitors the closing rate of the injector needle. On the basis of this information, an integrated correction function then ensures compliance with the nominal injection values throughout the lifetime of the injector.” To meet the stringent particulate number and mass emissions limits of Euro 6c, precision injection control is vital. It holds the key to achieving the required spray preparation and penetration characteristics under all combustion chamber conditions. And this precision is set to become even more crucial in the future, as new test methods like WLTC (World Harmonized Light Duty Driving Test Cycle) and RDE (Real Driving Emissions) put greater emphasis on transient conditions (load change). “Such dynamic variations in injection and combustion conditions can have a significant effect on fuel consumption,” says Lowack, “which demands even more of the injectors.”