When it comes to engine overhaul, the first thing that many car owners think of is stuffy cylinder. In the past engine overhaul, boring cylinder was almost a necessary process. With the continuous progress of engine technology, the application of boring cylinder technology is less and less.

What is an engine boring cylinder? ?

When the cylinder wall of the engine is excessively worn or even pulled off, the air tightness will be reduced, resulting in engine oil combustion and engine power loss. Boring cylinder is to cut the worn inner wall of cylinder smoothly, reduce roundness, and make the piston and cylinder wall work closely together and run smoothly in the cylinder.

How to bore the engine cylinder?

1. Boring cylinder is to process the inner wall of the cylinder to make it smooth again, so as to closely cooperate with the piston. Because the surface of the cylinder wall is "polished" with a thin layer, it will inevitably lead to a slightly larger cylinder diameter, which is also commonly known as "greater displacement".

2. If the bore diameter of the boring cylinder increases by 0.25, it can be increased to 0.75 at most, so the cylinder liner needs to be replaced.

3. After the repair size of the cylinder is determined, you can choose the pistons of the same level (there are 6 repair sizes for gasoline engines and 8 repair sizes for diesel engines), and the difference between each size is 0.25mm, increasing step by step. At present, the cylinder is generally bored according to the selected piston, that is, the outer diameter of the selected piston skirt is measured first, and then the boring amount is calculated according to the actual size of the piston and cylinder. The method is as follows: boring amount = maximum diameter of piston skirt-minimum diameter of cylinder+clearance between piston skirt and cylinder wall-cylinder grinding allowance.

Why are there few boring cylinders during engine overhaul?

1. engine technology and process improvement

Due to the continuous progress of engine technology and manufacturing technology, the probability of abnormal engine wear is very small, and generally it will not reach the level of boring cylinder.

2. Promotion of aluminum alloy cylinder liner.

Now more and more models are using all-aluminum engines, that is, the engine cylinder is made of aluminum alloy. The cylinder block of low-end all-aluminum engine is usually equipped with cast iron cylinder liner, while the high-end engine adopts thermal spraying technology to spray special coating directly into the aluminum alloy cylinder bore to replace the cylinder liner. These two kinds of aluminum alloy cylinder blocks are not suitable for boring cylinder processing, so the boring cylinder of all-aluminum engine is rarely repaired.

3. The change of maintenance concept

Auto parts are easy to buy and cheap, and the auto parts market also gives car owners more choices, such as disassembling and remanufacturing parts. Compared with the traditional maintenance of boring cylinder, many car owners are more willing to accept the overall replacement once and for all.