The work is aimed at increasing the reliability, accuracy, information content and depth of the process of diagnosing the cylinder-piston engine group.
For this, an automated diagnostic system has been developed, which includes a system unit with a monitor, special software for measuring and processing information, a measuring analog-to-digital module, adapters for connecting to the engine. The diagnostic system allows you to record the change in pressure of the cylinder for every degree of rotation of the crankshaft with an error that does not exceed 1.7%. Measurements are performed in test mode, when the crankshaft of the engine is scrolled with a starter, and strain gauges are screwed in place of spark plugs. The measurement results are presented in the form of diagrams, text and digital values. The system also allows you to save, reproduce and transmit diagnostic information in digital, graphic and text form.
Using the developed diagnostic system, the engines of automobiles of various brands with a compression ratio in 9.5-10.5 units, with an engine capacity of 1.2-2.8 liters, with two, four and five valves for each cylinder were investigated.
In the course of experimental studies, the most common malfunctions were: burnout of the exhaust valve, loose seating of the valve in the seat, deformation of the valve stem, violation of a thermal clearance in the valve mechanism, piston scuffs, cylinder wall scorings, loss of elasticity or breakage of compression rings, deformation and kink of the piston baffles, wear of the cylinder in the top dead center location, wear of the piston rings and piston grooves.
Based on the obtained experimental data, here is established an objective relationship between specific engine malfunctions and diagnostic parameters.
The analysis of pressure changes in the cylinder at each degree of rotation of the crankshaft with help of diagrams allows the diagnostician to evaluate more objectively the technical condition of parts that ensure the tightness of the engine's operating process.