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Selection And Matching Of Internal Combustion Engine Piston For Diesel Generator

Feb. 24, 2023

1. Measurement of piston skirt.

The maximum wear, taper and out-of-roundness of the piston skirt can be measured with an outside micrometer or a dial indicator.


It is worth noting that when measuring the piston, the front and rear and left and right values should be measured at the upper, middle and lower parts of the piston skirt. The difference between the maximum and minimum values of the piston longitudinal diameter measured is the conicity, and the difference between the maximum and minimum values of the cross section diameter is the out-of-roundness, and then the comparison should be made according to the technical requirements of the instructions to see whether it can continue to be used.


2. Check the radial clearance between piston skirt and cylinder wall.

The radial clearance between piston skirt and cylinder wall is clearly specified by each machine. The inspection method is as follows: select a feeler gauge with appropriate length and thickness equal to the measured clearance size. The piston is upside down and the feeler gauge is placed on the piston skirt. At the same time, install the cylinder (at this time, the piston is not equipped with a piston ring. If the used old piston and old cylinder are used, they should be placed at the place with the largest wear). After they are in place, pull out the feeler gauge and pull it out by hand. It is appropriate to have a little resistance.


generating set

3. Check and adjust the height of the compression chamber.

(1) Definition of compression chamber height: The so-called compression chamber height refers to the distance (clearance) between the piston crown and the cylinder head when the piston reaches the top dead center, also known as the clearance of the compression chamber.


When repairing the internal combustion engine, if the cylinder sleeve, connecting rod, connecting rod bush, piston pin bushing, cylinder gasket and other parts have been replaced or repaired, the height of the compression chamber should be checked and adjusted.


(2) Check the height of the compression chamber by placing a lead block or lead wire on the piston crown (avoid the valve), tightening the cylinder head to the specified torque, and then slowly turning the crankshaft to make the piston pass the top dead center. Finally, take out the lead block (or lead wire) and measure its thickness with a micrometer. This thickness is the height of the compression chamber.


Note: The height of the compression chamber must be checked after the connecting rod bearing bush is repaired. The measured height of the compression chamber cannot exceed 5% of the specified value of the original machine.


(3) Adjustment of the height of the compression chamber: Generally speaking, gasoline engines use the thickness of the cylinder gasket to adjust the height of the compression chamber. The cylinder gasket is thickened, the height of the compression chamber rises, the cylinder gasket is thinned, and the height of the compression chamber decreases. The diesel engine is adjusted by the thickness of the gasket between the connecting rod bearing shells. The gasket is thickened, and the height of the compression chamber decreases. The gasket is thinned and the compression chamber height rises.


4. Piston selection.

The selection of piston should be determined according to the repair size of the cylinder. Since the cylinder has six repair dimensions, the piston also has six corresponding repair dimensions: 0.25mm, 0.50mm, 0.75mm, 1.00mm, 1.25mm, 1.50mm. When selecting pistons, it should be noted that the pistons of the same brand should be selected on one internal combustion engine, so as to make the material, performance, weight and size consistent. The diameter difference of the same group of pistons shall not be greater than 0.025mm; The weight difference of each piston shall not exceed 1%~1.5% of its own weight. All models have clear regulations.


Founded in 1974, Jiangsu Starlight Electricity Equipments Co.,Ltd., a wholly-owned subsidiary of Jiangsu Starlight Power Group, is one of the earliest manufacturers of generating sets in China. Over the past 40 years, the company has won the recognition of users by relying on advanced testing equipment, modern production technology, professional manufacturing technology, perfect quality management system, strong R&D technology strength. For more details, please contact us with sales@dieselgeneratortech.com.

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