Spark-ignition and diesel engines are being supercharged more and more – this “downsizing” cuts fuel consumption as well as CO2 emissions. This is why our charge-cycle experts are hard at work on new supercharging processes and variable valve trains. Cylinder cutoff complements downsizing and additionally increases efficiency through the associated load-point shift. Also of interest for modern SI engines is the Miller/Atkinson process that reduces throttling losses at part load and the tendency to knock at full load – making it possible to increase the degree of engine downsizing which permits a further reduction in swept volumes. Using cylinder-selective, multiple valve-lift changeover, we can realize all of these processes for boosting efficiency in a system.
Optimized charge cycle as the key to low-emission diesel combustion
Optimum charge cycle – coupled with ideal charge motion or mixture formation – is essential for low-emission and, in particular, low-soot diesel combustion to deliver a high level of efficiency. It is against this backdrop that we are working on various components at the advance-development stage (such as charge exchange and motion devices, supercharging unit, cylinder head with port geometry, combustion chamber geometry with piston recess) and combining them to create all-embracing overall concepts with optimum performance in terms of emissions and fuel consumption. Calibrating these complex systems at varying engine speed and load is increasingly being supported by model-based engine management approaches. Even today, our developers are exploring control structures that use cylinder-pressure-controlled engine management in combination with a variable valve train for optimizing the charge cycle in respect of the described objectives in real time too.