In advancing spark-ignition engines, we concentrate on improving efficiency and cutting emissions. One of our focal activities is downsizing: To permit even higher boost pressures without knock and pre-ignition, we analyze homogenized mixtures at injection pressures of 300 to 400 bar and variable compression ratios – either with mechanical systems for altering the geometric compression ratios or on the basis of the Miller/Atkinson cycle (variable effective compression ratio).
Quality-controlled SI engines for greater efficiency
At high vehicle speeds, lean combustion processes of the type found in the quality-controlled spark-ignition engine are up to 30 percent more efficient than downsized engines. With them, load is not controlled using the throttle valve but – in a similar way to the diesel engine – by means of mixture composition. We are working hard to improve this highly promising concept and take it to mass-production level. This necessitates new ignition concepts, like corona ignition, that reliably ignite lean mixtures.
New combustion processes with low emissions
Our experts are also focusing on new, forward-pointing combustion processes, such as CAI (Controlled Auto Ignition). Here, slightly lean mixtures with high residual-gas components ignite spontaneously – producing a very high level of efficiency in conjunction with low nitrogen-oxide emissions, obviating the need for any NOx adsorption catalyst.