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Adopting the contact finite element method, with complex connecting rod group assembled body model of computation, the fatigue strength of the connecting rod of a certain type of diesel engine was verified. A transient stress analysis was conducted on the connecting rod. Compared with the connecting rod static stretching and compression test, the contact finite element method, which was used to analyze the strength of the connecting rod subassembly, was feasible. Based on the contact finite element method, the connecting rod transient stress analysis results showed that the maximum stress of the connecting rod did not occur under the highest pressure of the cylinder, and the dynamic stress value was greater than the static stress value.

Adopting the finite element software ANSYS, this paper calculates the temperature and stress fields of the combined piston under the conditions of cooling and no cooling. The analytical results show that the piston under no cooling condition has higher thermal load and integrative stress than the condition of cooling, because the piston head can’t get better cooling. Moreover, the high thermal load causes the piston head creating great deformation, which has exceeded the normal gap between the piston and the liner, so the piston abrasion may worsen.

The structure and properties of diesel fuel injection system directly influence the performance of diesel, and calculation and analysis are important methods to improve engine performance. So, by analyzing the structure, math models and working process theory of the electronic control PPVI fuel injection system, this paper founds initial and improved simulation models of the diesel electronic control PPVI fuel injection system, completes simulation and analysis. The simulation results show that the improved model has better cushion effect than the initial model by adding a constant pressure delivery valve between the nozzle and electromagnetic valve, what is more, the improved model can avoid the instability of the work state, such as second injection, cavitation and anomaly injection, etc., therefore, the diesel forms perfect unloading characteristic, and its performance has also been improved.