**4. A case study: The effects of Y2O3 with coatings of combustion chamber surface on performance and emissions in a turbocharged diesel engine**

In this study, the effects of ceramic coating of combustion chamber of a turbocharged diesel engine to engine performance and exhaust emissions were investigated. Increasing mechanical energy by preventing heat losses to coolant and reducing cooling load, improving combustion by increasing wall temperatures and decreasing ignition delay, more power attaining in turbocharged engines by increasing exhaust gas temperatures and decreasing carbon monoxide and soot are aimed. For this aim, cylinder head, inlet and exhaust valves and pistons of the engine were coated with 0.5 mm zirconia by plasma spray coating. Then, the engine was tested for different brake loads and speeds at standard, ceramic coated engine one and ceramic coated engine 2 conditions. The results gained from the experimental setup were analyzed with a computer software and presented with comparatively graphics. Briefly, specific fuel consumption was decreased 5-9 percent, carbon monoxide emission was decreased 5 percent, and soot was decreased 28 percent for a specific power output value. Considering these positive results nitrogen oxide however was increased about 10 percent. By the development of exhaust catalysers, increase in nitrogen oxide becomes no more a problem for present day. When results are generally investigated, it was concluded that engine performance was clearly improved by zirconia ceramic coating.
