Piston Clearance of IC Engine

Piston Clearance Points : Piston Clearance Pistons are typically little in diameter than the bore of the cylinder. The space flanked by the cylinder and the cylinder wall is called the piston clearance. This clearance is necessary for the following reasons.
1. It provides a gap for a film of lubricant between the piston and cylinder wall to reduce friction.
2. It prevents piston seizure. Due to very high operating temperature, piston and cylinder block expand. The cylinder is cooled better than the piston, hence sufficient clearance should be provided for the piston to expand, failing which the piston seizure will result.
3. If there is no clearance between the piston and cylinder, it will be not possible for the piston to give in return in the cylinder.

The quantity of piston clearance depends upon the size of the cylinder bore and the metal used in the piston. But it is generally 0.025 mm to 0.100 mm. In operation, this clearance is filled with oil so that the piston and rings move on films of oil. Proper clearance should be maintained between the piston and the cylinder wall. If the consent is too small, there will be pasting of power from extreme friction, severe wear and possible seizure of the piston in the cylinder, If the clearance is too much, piston slap will result. Piston slap means sudden tilting of the piston as the piston is down on the power stroke. The piston shifts from one side of the cylinder to the other with sufficient force to produce a distinct noise. As the piston warms up the clearance is reduced and the noise usually disappears. In order that fixed clearances may be old without risk of attack, special alloys have been introduced and many designs of piston are in use. These particular designs involved cam grinding to non-circular forms, semi-flexible skills incorporating oblique’s slits, controlled distribution and the like expedient.