Investigation Regarding the Influence of a Catalytic Combustion Chamber Coating on Gasoline Combustion Characteristics, Emission Formation and Engine Efficiency 2012-01-1097

Over the past few years, both global warming and rising oil prices led to a significantly increased demand for low fuel consumption in passenger cars. However, the necessity to also meet the limits of today's and future emission regulations makes it more and more difficult to maintain a high engine efficiency without the use of an expensive external exhaust gas after-treatment system. Therefore, new technologies that simultaneously prevent emission formation and reduce fuel consumption inside the internal combustion engine during the combustion process itself are of highest interest.

This paper analyzes the influence of a catalytic coating of the combustion chamber on combustion, emission formation and fuel consumption. For this purpose, test runs with a production 2.0-liter, 4-cylinder, 4-valve, double overhead camshaft (DOHC), port fuel injection (PFI) gasoline engine were performed. The various possible benefits of the catalytic coating mentioned above were separated by different engine setup combinations. The coated configuration was optimized in terms of its part load performance with special focus on fuel consumption and emissions, and thereafter compared to the baseline engine configuration. Subsequently, the optimization results were used for a simulation of the fuel economy during an FTP75 cycle. Additionally, an in-depth analysis of the combustion process of the different configurations using indication data and emission measurements was performed.

The analysis of the performed tests shows an increase of combustion speed shortly after ignition using catalytic-coated engine parts. This leads to a steeper and higher pressure gradient and hence better combustion stability under lean conditions. The coating and especially the possibility to change maximum brake torque (MBT) spark timing due to the changed combustion characteristics caused by the coating also affect NO_X and HC emissions at some load conditions.