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 NOX and HC
emissions at some load conditions.