Regarding the test steps of the fuel injectors that were released last time, many customers feedback that it only had test steps on a computer, and wanted to see the specific test bench operation steps. In the common rail test bench, the injector test goes by 4 or 5 steps: Leak test, VL, LL, VE, EM ,Pre-injection, today we talk about these step’s meaning, and how it affects the engine’s performance.
LEAK TEST: Sealing test
In this step, the control system does not trigger the injector. The pressure rises slowly from 0bar to a maximum pressure of 1600 bar. Seeing with eyes, if the nozzle is free from dripping fuel, The injector housing has no leakage. The system simultaneously measures the static fuel return to judge if the high pressure seal ring, ball and seat damaged or not ( in this step if the nozzle dripping fuel, engine will emit black smoke, work violent, the fuel return volume bigger will cause difficult start, frequent flameout, speed limit, metering unit exceeds the maximum value).
VL: Full load fuel quantity
This step simulates the engine full-load fuel injection, and the system flow sensor accurately detects the fuel injection amount and the return amount. The displayed flow rate is the single injection value of the injector. The effect of the amount of fuel injection is the same as that of the Euro 2 system. The DNH gasket in the injector is adjusted to save fuel. The amount of fuel return is further detected whether the control valve set of the common rail injector is damaged.
TL\EM Average point\Drain point\Exhaust gas limit fuel supply ( all are same, just different description)
This step is similar to the torque of the traditional Euro 2 system torque point, and achieves the purpose of discharge.
If the amount of fuel is too small, the engine is weak, the speed is slow, the power is insufficient, the smoke is too large, and the emission standard is not reached. The AH, DNH, VFK, and DFK gaskets can be adjusted to obtain a satisfactory acceleration curve.
LL: Idle fuel supply
Simulate engine idling conditions, this step should ensure that the idling fuel is in the range.
Within the perimeter, if the consistency is not good, the speed is unstable, and it is easy to flame out and the noise is loud. Larger idling fuel quantity causes excessive speed and smoking, if small idling fuel quantity ,engine is easy to flame out, not easy to start the engine or slow down!
VE; pre-injection
Pre- injection is a small amount of fuel injected into the engine before injection.
Heat, reduce noise, better for cold start, reduce emissions, pre-injection bigger will increase noise knocking, engine blue smoke, too small will cause start difficulty, there is acceleration noise when engine acceleration , acceleration is not smooth, more violate for acceleration.
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