Optimizing the Cylinder Running Surface / Piston System of Internal Combustion Engines Towards Lower Emissions 2012-32-0092

Rising fuel prices and more stringent vehicle emissions requirements are increasing the pressure on engine manufacturers to utilize technologies to increase efficiency and reduce emissions. As a result, interest in cylinder surface coatings has risen considerably in the past few years. Among these are SUMEBore® coatings from Sulzer Metco. These coatings are applied by a powder-based air plasma spray (APS) process. The APS process is very flexible, and can process materials which wire-based methods cannot, particularly metal matrix composites and pure ceramics. Applications range from small 2-stroke engines, motorcycles, and lightweight passenger car engines, up to high-speed diesel truck engines and medium-speed diesel engines.

The compositions of the coatings can be tailored to the specific challenges in an engine, e.g., excessive abrasive wear, scuffing, corrosion caused by adulterated fuel, improved heat transfer from the combustion chamber into the water jacket, etc. A number of engines have been tested successfully. Most of them exhibited significant reductions in lube oil consumption (LOC), reduced fuel consumption, very low wear rates and corrosion resistance on the liner surfaces. This coating solution has been commercialized in various markets. It has proven to be suitable for mass production on both new engine blocks and liners, and for repair of worn-out parts. Such coatings will continue to play an important role when it comes to reductions of weight and emissions in internal combustion engines. An example of such a coating solution will be outlined. It has been carried out in collaboration with BRP Powertrain in Austria on a 1.5L 3-cylinder aluminum engine and together with the adjustment of the ring package and the piston a reduction of 35% in LOC was achieved. This engine will go into production in September 2012 with limited numbers coated in the Sulzer Metco Wohlen facility in Switzerland, until an engineered coating system is ready on site to start large series production. More details on the engine performance and design changes made to the cast aluminum block in order to take full advantage of the coating on the cylinder running surfaces is presented in the paper from Zorn et al.