1. Classified according to the top structure of Bitzer 4PC piston

①Flat-top piston: suitable for pre-combustion chamber of carburetor engine and vortex combustion chamber of diesel engine. The advantages are that it is easy to manufacture, the top bears the heat evenly, and the piston mass is small.
②Recessed piston: It can improve the flow performance and combustion performance of the mixed gas, and is suitable for diesel engines or some gasoline engines. The advantage is that it is easy to change the compression ratio and the shape of the combustion chamber.
③Protruding piston: In order to increase the compression ratio, it is generally suitable for low-power engines.

2. Classified according to the structure of Bitzer 4PC piston skirt

①Skirt grooved piston: suitable for engines with small cylinder diameter and low gas pressure. The purpose of slotting is to avoid expansion, also called elastic piston.
② Pistons with non-grooved skirts: mostly used in the engines of large-tonnage trucks. Also called rigid piston.

3. Classified by Bitzer 4PC piston pin seat

① Pistons where the axis of the piston pin seat and the axis of the piston perpendicularly intersect.
② Pistons where the axis of the piston pin seat is perpendicular to the axis of the piston but does not intersect.