The engine piston should bear the considerable mechanical pressure.As the engine performance is enhanced in the recent years,the working environment of piston has been become very harsh,e.g.heat load(the speed of increasing power should excess 50KW under the circumstance of 2600°C instantaneous temperature in the combustion chamber)and average ignite perssure have been raised much.We meet the need of "lighter piston,lower oil-consumption and enough rigidity & intensity caused by high running-up and longer piston path.