Which of the following types of pistons use bushingless pin bosses?

The correct response is based on the design features of the Monotherm piston. Monotherm pistons are engineered without bushings in the pin bosses, which is advantageous for reducing weight and simplifying the assembly process. This design allows for a more direct connection between the piston and the connecting rod, thereby also improving performance and efficiency.

The absence of bushings in Monotherm pistons means that there is less friction and wear at the pin boss, leading to enhanced durability over time, particularly in high-performance applications. These pistons are often used in modern engines where space and weight savings are critical, as well as in applications where reducing the number of components can enhance reliability.

This design characteristic distinguishes Monotherm pistons from other types that may include bushings to support the pin, which can lead to increased friction and require more maintenance.