26 Development of “BF-Coat” for Snowmobile Piston

The pistons in a snowmobile engine are subjected to severe temperature conditions not only because snowmobiles are operated in extremely cold temperatures but also because the engine has a high output per unit volume of approximately 150kW/liter. The temperature of the piston top may go from -40°C (when a cold engine is started) to 400°C or higher (when the engine is running at full load). When the piston and cylinder inner wall are cold, the performance of the lubricating oil drops; when they are hot, scuffing may be produced by problems such as tearing of the oil film between the piston and cylinder. When the engine is run at full load for a long time, moreover, the piston is subjected to prolonged high-temperature use, which is conducive to the production of piston boss hole abrasion and ring groove adhesive wear.

There are many piston surface coatings available to resolve these problems, but we use BF-Coat (Black-Fluoro Compound Coating) on the pistons in our 2-stroke snowmobile engines. BF-Coat has the abrasion resistance of anodic oxide coating and excellent sliding characteristics. By coating the entire piston surface with BF-Coat, we have developed a high-quality piston with a more scuff-resistant skirt and abrasion-resistant pin hole, and a ring groove that is more resistant to adhesive wear.