Amongst keeping the stringent exhaust emission standards, the significant reduction of fuel consumption is dominating future engine development. In order to influence the fleet consumption significantly, especially inexpensive concepts applied to mass production are required.
Considering SI engines, one of the main issues is the reduction of pumping and heat losses during part load operation. This can be achieved on the one hand by shifting the engine main operation range to higher loads and lower speeds during city cycle driving due to long final gear ratios. In order to meet the vehicle acceleration demands simultaneously, a low end torque orientated full load characteristic is indispensible. On the other hand, the traditional way of downsizing combined with higher speeds under city driving conditions offers also potential for improving fuel economy.
Based on flow tests, engine investigations and cycle calculations, the potential of an inexpensive fuel economy concept will be demonstrated and evaluated in comparison to a conventional downsizing concept.