The meaning of cylinder ovality limit is what many are longing to know which will be discuss in this article.
Cylinder ovality limit is the deformation that, after a prolonged period of operation, the liner of a cylinder presents.
It is caused by the irregularity of the lateral thrusts of the piston in its travel.
It really surprised me that my engine started consuming engine oil after I just replaced the piston rings.
When I measured my cylinder diameter, I noticed cylinder ovality limit which is deformity of the liner. To fix my engine, I have to replace the engine liner.
Here is a video that will also help you in the understanding cylinder ovality limit.
I will like to share my experience with you below.
What Is The Meaning Of Cylinder Ovality Limit
The pistons, in their movement inside the cylinder, generate wear.
One might think that, since said movement is vertical, the wear generated will be regular and homogeneous, but this is not the case.
Cylinder ovality limit is a consequence of irregular wear and manifests itself in the loss of the circular shape of the cylinder with use.
If two measurements of its diameter are made so that one is perpendicular to the other, two different lengths will result.
Specifically, the cylinder walls that experience friction perpendicular to the crankshaft axis will show greater wear.
As a mechanic, you can likewise measure the cylinder ovality limit with your macrometer or calipers. Let me show you how I measure the cylinder ovality limit below.
To measure the cylinder deformity, follow the following steps:
To measure the cylinder deformation tolerance you will need to remove the piston from the cylinder so as to take proper measurements.
You can make good use of calipers to do the measurements, or you can likewise use micrometers as a measurement tool.
You also need to clean the cylinder wall so as to have accurate measurements.
To measure the cylinder ovality limit, you need to measure the upper diameter, the middle diameter, and the lower part diameter.
Record all your measurements and check the measurements to see if there is cylinder deformation tolerance.
Similar steps can also be used to measure the cylinder roundness specification, but with a different tool.
The tool will be mentioned below.
How Piston Movement Causes Cylinder Ovality Limit
The piston’s top dead centre is when it receives the vertical pressure caused by the explosion.
In its downward movement towards the bottom dead centre, the inclined position of the connecting rod generates a lateral thrust that causes greater abrasion or wears on one of the sides of the cylinder, the one located on the opposite side of the connecting rod head.
Similar wear will occur on the compression stroke.
In this case, the piston travels upwards from the lower dead centre and receives the pressure of the gases that are being compressed in the chamber.
Again, the position of the connecting rod causes an abrasion on one of the walls, which now turns out to be the opposite of the one affected during the explosion.
The intensity of one and the other wear is not the same since the friction caused during the detonation is more pronounced than in the compression, as the force acting is greater.
How Is Piston Ovality Measure
The largest application of the alesometer is found in machining, where it is the specific tool to measure the internal diameter of engine cylinders and the ovality and conicity in the cylindrical surfaces.
The ovality is the difference in diameter from the cylinder at the same height due to lateral thrust forces generated during combustion on the piston.
The conicity is the difference in diameter that the cylinder has at different heights since it wears more in the upper part than in the lower part due to the increase in combustion pressure, the high temperature generated and the reduction in lubrication.
When the ovalization of the cylinder reaches appreciable values (difference between 2 diameters, at 90° to each other, greater than 0.05 mm), the rings fail to guarantee perfect retention along the walls.
The passage of oil into the combustion chamber grows with an increase in lubricant consumption proportional to the number of revolutions of the engine.
What Is The Reason For Cylinder Liner Ovality
There are several reasons for cylinder liner ovality; let me briefly mention some of them.
- Wear and tear: this is one major reason why your cylinder liners have ovality. As the piston is traveling up and down, the wear will surely set in with time.
- Unbalanced cylinder loading: if the loading of a cylinder is uneven and is causing the piston to move from right to left,
- Overloading: If the cylinder is overloaded, it can cause the conrod to have uneven thrust.
- A damaged piston: If the piston is damaged, it will cause the liner ovality.
- Solid substance formed in the cylinder: when the engine is working, carbon may be formed; such carbon can cause cylinder ovality.
Why Is It Important To Measure Cylinder Roundness Specification
To measure the cylinder wear: the more the engine is working, the more wear it has.
During repair or overhaul, you can measure to know if you need to replace the liner.
Oil Consumption: If your engine begins to consume oil, then you need to measure the cylinder liner to see the extent of the wear.
Signs of scuffing: if you notice a scuff in your cylinder liner, you need to measure to ascertain if the liner is still good.
Which Precision Instrument Is Used For Measuring Cylinder Ovality Limit
There are two major instruments that can be used to measure the piston ovality.
- calipers
- micrometer
These are the two major instruments used to measure the piston ovality.
Now let’s talk about how to measure it.
Follow the steps below.
- Remove the rings from the piston.
- measure the axial heights of the piston.
- measure the radial width of the piston.
- measure the piston skirt
With those few steps, you can measure the piston ovality with any of those aforementioned tools.
What is Ovality in Piston?
Piston ovality is a deformation that happens to the engine piston over a prolong period of work . It may be caused by excessive heat, solid substance presents in the combustion chamber such as carbon, or by a damaged liner.
This is a situation where the piston can no longer maintain it roundness due to wears that occurs during the engine operation.
You may wrongly think that the cylinder supposed to maintain its original round shape despite wearing, but it is not always like that.
You will notice this when you measure the piston axial heights and radial width of the piston. it is then you will notice differences.
What Are The Symptoms Of Cylinder Ovality Limit
Below I will listed symptoms of cylinder bore wear for you.
1. Oil Consumption: One of the things you are going to observe is that your engine will be consuming a lot of oil during operation. Instead of the oil to be recycling, it will be consuming.
2. Blue Smoke: Blue smoke is as a result of oil consumption. You will see blue smoke from your talepipe, which is a sign of oil burning.
3. Low Compression: This is another symptoms of wear bore.
4. Engine lack of power: If your engine lack power, lack efficiency, it is a sign of wear cylinder bore.
Final Thought
I hope this article has broaden your knowledge on cylinder ovality limit. You have learn how to measure cylinder ovality.
The article also briefly mentioned what is piston ovality.
From the article you have also learn how to measure the cylinder ovality limit. Don’t forget to take note of those factors that causes cylinder deformation tolerance.
I also explained the symptoms of cylinder ovality
There are other related article on engine cylinder
Do you measure the cylinder roundness specification?