Abstract
Keywords - Gasoline Direct Injection, Downsizing, Downspeeding, Turbocharging, Fuel Economy
Improved fuel economy respectively reduced CO2 emission are the major challenge with future passenger car powertrains. For most cost effective concepts, the combustion engine, gearbox and hybridization have to be developed not separately, but as a complete system approach.
With Gasoline engines, besides general measures like reduced parasitic losses, improved thermal management etc., especially downsizing / downspeeding concepts based on turbocharged GDI offer best cost effectiveness. The most significant challenges for such fuel efficient turbocharged GDI are improved low end torque and transients, reduced enrichment at high load and enhanced part load efficiency
Applying most refined single stage charging, full engine torque already at 1250 rpm can be combined with a spec. power of 80kW/l. With dual stage charging, BMEP levels > 30 bar and also spec. power > 140 kW/l can be obtained. New measures for exhaust cooling like integrated exhaust manifold, water cooled turbine housing and/or cooled external EGR at high load result in significant improvement of real world fuel economy. As a second step also spray guided stratified charge systems or controlled auto ignition can be considered. To gain sufficient cost effectiveness, however, their characteristics have to be improved towards better high load efficiency
Thus the combination of GDI + Turbocharging is the ideal basis to combine high real world fuel economy with excellent fun to drive even under a stringent CO2-scenario.