The hydraulic impact force directly causes the deformation of the precision pair. For the Fuel injector with a rated working pressure of 160MPa in the high-pressure common rail system, when the Fuel Pump abnormally generates a transient pressure wave of 220MPa, the impact kinetic energy of the nozzle needle valve increases by 89%. The measured results show that an overpressure lasting only 0.5ms will cause the plastic deformation of the valve seat to reach 3.2μm (tolerance limit 1μm), and the width of the sealing tape expands from 0.25mm to 0.38mm, causing the dripping rate to rise to 46 drops per minute (standard value ≤2 drops).
The stress over-limit of the sealing structure accelerates the failure. The stress of the Bosch piezoelectric fuel injector sealing steel ring is 320MPa at a pressure of 350bar, but when the pressure rises to 420bar, the circumferential stress reaches 85% of the ultimate strength (520MPa). The ECU data record of a certain logistics fleet shows that after more than 25 abnormal supercharging events, the fatigue crack growth rate of the sealing ring reaches 2×10⁻⁸m/cycle, and the fuel leakage volume increases by 400ml per month, equivalent to an additional consumption of 7.8 tons of diesel per year.
High-frequency vibration causes lattice damage to the material. When the pressure fluctuation frequency coincides with the characteristic frequency of the fuel injector (approximately 2800Hz resonance point), the amplitude is amplified by 5.7 times. Fiat Powertrain Technologies Laboratory discovered that in a pulsation environment of 210bar±35bar, the charge of the piezoelectric crystal stack decreased by 28% after 5 million cycles, resulting in the fuel injection pulse width control error increasing from ±0.03ms to ±0.15ms, and the air-fuel ratio deviation reached 14.7% (exceeding the standard by 6 times).
The temperature-pressure coupling effect intensifies corrosion. When the EGR reflux gas raises the injection environment temperature to 240℃, the diesel pyrolysis at a pressure of 280MPa produces a formic acid concentration of 0.15%. This caused the corrosion rate of the ceramic needle valve material (ZrO₂) to soar from 0.8μm/1000h to 5.3μm/1000h, and the measured nozzle life of Volvo trucks under extreme working conditions was shortened to 80,000 kilometers (the designed life was 500,000 kilometers).
Impurity wear is significantly magnified under high pressure. In a system with a filtration accuracy of 10μm, particles of 5-8μm account for 17%. Calculations show that a pressure of 200MPa causes the particle impact energy to increase to 28 times that of the atmospheric pressure system, increasing the wear rate of the valve seat hardening layer (HV1050) by 0.12mg per thousand times. The engine repair data of Cummins X15 shows that when operating under overpressure, the diameter of the spray hole expands to 0.155mm (originally 0.128mm), and the atomization cone Angle decays by 9.8°.
The overshoot risk of the electronic control unit needs to be taken into account. When the regulating valve of the Bosch MED17 system fails, the control deviation of the oil rail pressure can reach ±42bar. The simulation shows that when the output pressure of the high-pressure oil pump instantaneously exceeds 205bar, the pressure control drive current needs to be compensated by 23.7A within 0.3ms, exceeding the maximum output current of 18A of the ECU by 32%, resulting in magnetic field saturation and triggering an event where the fuel injection volume increases by 32% out of control.
Maintenance data reveals the correlation pattern. A diesel engine overhaul center statistically analyzed 400 faulty fuel injectors: for units with a 10% deviation in pressure sensor accuracy, the frequency of fuel injector replacement was reduced from 150,000 kilometers to 43,000 kilometers. ISO/TS 16949 requires the calibration of rail pressure sensors every 80,000 kilometers (with an error of ±2bar), which can reduce the risk of abnormal high-pressure damage by 63% and save ￥18,600 in maintenance costs for each engine.