1. Pistons

1.2. Piston Design

LO 7-02: Classify pistons according to their application, design, construction features, and material.

 

Piston Design

Pistons have three main parts:

  • The crown, or top of the piston, which is subjected to cylinder pressure and heat.
  • The ring belt, which is where piston ring grooves are located.
  • The skirt, which is the surface that slides directly against the cylinder wall to stabilize piston movement Figure 5.

In the uppermost part of the skirt is the piston pin. Additional piston material reinforces the area around the pin and is called the pin boss Figure 6. Steel struts are often cast into the pin boss for improved strength.

Their shape, construction method, and materials today categorize piston designs. Several basic piston designs used in today’s diesels are made from either aluminum or steel alloy material, including slipper skirt, cam ground, trunk, articulating, and newer single piece mono steel alloy pistons Figure 7.

   Fig07_5

FIGURE 07-5: The main sections of a piston.

 

Fig07_6

FIGURE 07-6: Piston nomenclature. The connecting rod and piston are forged.

   Fig07_7

FIGURE 07-7: Major types of piston designs used in today’s HD diesel engines include steel alloy, trunk, and articulating.

 

©2026 - CDX