Advanced GDI Injector Control with Extended Dynamic Range

Considering the world-wide market for GDI engines, the introduction of tighter polluting emission legislation, additional costs, vehicle fuel economy and pollutants reduction become substantial drivers. Focusing on particulate reduction, direct injection gasoline engines require advanced combustion strategies. The main levers used are injection splitting in order to reduce wall impingement (due to lower penetration) and higher rail pressure level to reduce droplet size. To reach this target it is necessary to improve precision in term of injected quantity in the small quantity region with high fuel rail pressure and during the actuation of multiple injections. As a consequence of the requirements of high quantities at full load, known GDI solenoid injectors show an unacceptable spread in terms of small injected quantity when the energizing time is small such that the injector works in the ballistic zone. Following these premises an electronic approach is needed. New hardware and software solutions should be integrated into the ECU in order to match the new injectors performance requirements. This paper presents two different strategies developed by Magneti Marelli: the first one is based on rail pressure measurement, the second one is based on injector electric signal analysis. Results in terms of correction of injected quantity using Magneti Marelli solenoid injectors are presented. The developed strategies demonstrate the possibility to work with multiple small injections at high pressure without changing injector hardware.