What is cylinder scuffing ?
Cylinder scuffing refers to the cylinder wall is pulled into a deep groove, the piston, piston rings and cylinder wall friction loss of sealing, which leads to cylinder compression pressure is reduced, power loss; Combustible mixture down to increase crankcase pressure, which can cause a serious crankcase explosion; The lubricating oil runs up to the cylinder caused by burning oil phenomenon occurs; exhaust pipe smoke serious; engine noise abnormal; engine can not work normally or even stalled.
cylinder scuffing is the engine piston or piston ring will be pulled into the cylinder work surface scarring caused by the piston, piston ring and cylinder wall friction vice loss of sealing phenomenon.
How do we know the cylinder is scuffing in a engine?
- The compression pressure of the cylinder decreases and the power is losing;
- Combustible mixture down to increase crankcase pressure, which can cause a serious crankcase explosion;
- Oil burning caused by the oil running up into the cylinder;
- Exhaust pipe smoke serious; engine noise abnormal; engine can not work properly or even stalled.
What causes cylinder scuffing?
- The fit clearance between piston and cylinder is too small
Piston and cylinder clearance should be in strict accordance with the provisions of the diesel engine manual with the clearance is too large, will make the diesel engine cold start difficult, when the engine is cold, there is a knocking sound and the power drops. gap is too small, it will cause pulling and expansion of the cylinder and other failures.
- Piston ring opening clearance is too small.
Piston ring opening clearance, back clearance is too small, ring and cylinder wall friction is too large, cylinder carbon serious and assembly defilement or oil is not clean and cause strain.
Piston ring opening gap is too small, the old cylinder for a new ring after the first ring hit the cylinder sleeve shoulder or assembly piston ring opening is too large easy to cause breakage.
Side gap is too small, disassembly and installation did not use special tools, so that the ring appears spiral, resulting in elastic effect or serious carbon accumulation in the cylinder, will lead to live The plug ring will bite.
Piston ring opening gap, side gap is too large, twisted ring, tapered ring up and down direction installed in reverse, as well as lubricating oil is too dirty so that the oil channel hole blockage, etc. It is easy to lead to oil tampering.
- The piston ring is broken
Piston in the cylinder deflection is too large, resulting in elliptical and taper, the upper part of the step phenomenon cylinder liner inner wall working surface often in the piston ring movement area to form uneven wear over the limit, generally in the reciprocating direction to form a cone, in the circumferential direction to wear into an irregular ellipse.
In the cylinder liner wear the largest amount of position, the ellipticity is often the largest, the cylinder liner and the piston ring does not contact parts do not wear, thus the obvious wear steps, in the work stroke gas pressure to force the piston to move down the stop, from reciprocating to rotating, the piston ring on the cylinder liner side pressure in the direction of the crank movement plane maximum The piston ring and the cylinder liner, which is perpendicular to the direction of the crankshaft liner wear maximum, crankshaft bending, connecting rod bending, cylinder liner centerline and crankshaft axis line is not perpendicular, crankshaft axial clearance is too large, can make the piston ring and cylinder liner produce eccentric grinding and uneven force and break.
If the engine bearing tile gap is too large, the piston pin, connecting rod copper sleeve clearance is too large, in the upper part of the cylinder liner there is obvious wear steps, the first air ring is most likely to break.
- Piston and piston ring are tilted to one side and pressed against the cylinder wall
Due to piston deformation, piston bore offset, cylinder grinding skewed, connecting rod curved or twisted, crank pin and main journal imbalance, when the piston pressure on the cylinder wall is relatively concentrated, the local surface, so that the cylinder wall and the oil film between the piston ring under great pressure becomes thin, or even rupture, thus losing Lubrication, the formation of dry friction caused the cylinder scuffing.
- Poor atomization of fuel injection nozzle for a long time
The fuel injector is the most precise part of the car, and the engine mainly burns gasoline when it is working.
In the combustion process due to high temperatures so that the surface or pores of the injector nozzle to produce carbon and at the same time more gum will also be deposited in the long-term use of the injector nozzle wall and needle valve surface, affecting the effect of oil injection, so that the injector nozzle blockage, adhesion, resulting in oil leakage, poor atomization, and even no oil injection, resulting in increased fuel consumption, engine power decline, unstable idle speed, poor acceleration and cold start difficulties and other phenomena.
Test data indicates that when 10% of the fuel injection volume is obstructed, it will lead to incomplete combustion of the engine, reduced performance, increased fuel consumption and higher exhaust temperatures. Incomplete engine combustion, performance degradation, increased fuel consumption and exhaust temperature rise. At this point, the injector should be cleaned in time to improve the combustion efficiency of the engine. The combustion efficiency of the engine.
- Piston cooling nozzle failure.
Individual engines live cold but rely on the connecting rod bearing to the piston pin piston nozzle oil injection engine. For various reasons, it does not spray oil properly, causing the top of the piston to melt and pull the cylinder. The top of the piston overheats and causes the top of the piston to melt and the cylinder scuffing.
Running an engine at a water temperature below 65°C is called cold running. Engine water temperature will start working before it reaches a certain level, or when the thermostat opens at too low a temperature, the cooling water enters the large circulation too early, which can cause too cold running. When the cylinder wall temperature drops from 800°C to 500°C, the wear of cylinder liner increases about 5 times.
And in the cylinder wall temperature reaches 800 ° ~ 850 ° C, wear significantly reduced. The water temperature is too low, diesel fuel in the combustion chamber temperature rise more slowly, stall combustion period is long, the combustion process deterioration, poor running performance.