What is the clearance between the piston and the cylinder wall?

The piston is divided into three parts: piston top, piston head and piston skirt. The piston head has a piston ring (gas ring oil ring), and the clearance between the back of the piston ring and the bottom of the ring groove is generally 0.5-1mm. 。

When the piston works in the cylinder, it needs to overcome high temperature and high pressure. Due to the thermal expansion of metal, the piston skirt is generally made into an oval tube, that is, the ellipticity of different parts of the piston skirt is different, and the ellipticity gradually increases from bottom to top, that is, the cross section of the piston skirt is flatter as it goes up, so as to reduce the resistance caused by thermal deformation of the piston.

The clearance between piston and cylinder of Santana car is 0.0 1.9 mm-0.039 mm as the standard and 0.025 mm-0.045 mm as the repair value. Other engines are different.