The stringent demands on reducing CO2 emissions mean that fleet consumption in Europe must be limited to 95 g CO2/km for an average vehicle weight of 1395 kg by 2020. In addition to electrifying drive systems, much more must be done to improve the efficiency of the combustion engine. As the gasoline engine will continue to account for the largest share of the world market, particular importance must be attached to this propulsion concept.
For gasoline engines to meet this ambitious CO2 goal, one main development trend is seen in reducing displacement in combination with supercharging (downsizing). Charge dilution with and without supercharging would open up further thermodynamic potential but for that the ignition limit must be shifted at high in-cylinder pressure. As a result, Improving ignition reliability and precision – with much leaner mixture quality and exhaust-gas recirculation rates – may be the key to further optimizing the gasoline engine. Outside the spark-plug ignition range, however, igniting such a highly diluted mixture poses a challenge.
Must the traditional spark plug be replaced by alternative systems, as current research projects suggest?