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The challenges of ever increasing combustion engine complexity coupled with the introduction of new and ever more stringent emissions regulations place a unique strain on the time available during the base engine hardware development and calibration phase of the product development cycle. Considering state of the art gasoline engine architecture (dual variable valve timing, direct injection with turbocharger) it is common to have at least 12 degrees of freedom as system inputs. The understanding of interactions and inter-dependencies of these inputs is therefore key in optimising the performance of the engine. MAHLE Powertrain has developed a process using a global Design of Experiment (DoE) technique based on Gaussian processes that can be used to accurately model and optimise many aspects of an engine’s performance.

Gasoline engine downsizing is one of the main technologies being used to reduce automotive fleet CO₂ emissions. However, the shift in operating point to higher loads which goes with aggressive downsizing means that real-world fuel economy can be affected by the amount of over-fuelling required to maintain exhaust gas temperatures within acceptable limits. In addition there is a drive to lower the exhaust gas temperature limit in order to reduce the material costs required for high temperature operation. A water-cooled exhaust manifold is one technology, which can be used to minimize the over-fuelling region. This paper investigates the effects of this technology applied to a twin-charger 1.4-liter gasoline direct injection engine. Data is presented which quantifies the benefits in conjunction with other downsizing technologies including cooled EGR and variable geometry turbochargers.