According to the SAE J2716 standard, the rated pressure range of modern Fuel systems is 3-5 bar (for gasoline engines) to 200-300 bar (for direct injection diesel engines), while the flow output of the Fuel Pump (such as 200 L/h) needs to be dynamically controlled by the regulator. To match the engine requirements. If the regulator is removed, the fuel pressure may fluctuate by more than ±20% (Bosch test data), causing abnormal operation of the fuel injectors. For instance, the ECU record of a certain American model shows that when the air-fuel ratio deviation reaches ±8%, the nitrogen oxide (NOx) emissions will exceed the standard by 40%, and the probability of triggering the fault code is as high as 90%.
In terms of economy, eliminating the regulator can reduce the component procurement cost by 500 to 800 yuan, but it comes with higher risks. In 2022, Volkswagen Group recalled 47,000 models equipped with the EA888 engine due to users’ self-modification of the Fuel Pump causing loss of control over fuel pressure. The maintenance cost per vehicle increased by 3,000 yuan (including the cost of replacing the high-pressure fuel rail). Studies show that the pressure of a fuel system without a regulator may soar to 7 bar at idle speed (exceeding the design limit by 40%), increasing the load of the fuel pump motor by 35%, sharply reducing its lifespan from 100,000 kilometers to 30,000 kilometers, and raising the failure rate by six times.
From the perspective of technical compliance, the National VI emission regulations require that the accuracy error of fuel pressure control be less than ±2%. However, after removing the regulator, the measured deviation can reach ±15% (test data from the Department of Automotive Engineering of Tsinghua University), which directly leads to the failure of vehicles to pass the OBD inspection, increasing the failure rate of annual inspections by 67%. Furthermore, a supply chain research of a certain Japanese enterprise shows that the Fuel Pump without a regulator may have a fuel vapor pressure exceeding 0.7 bar in a high-temperature environment (50°C), causing the carbon canker to overload and the fuel evaporation emissions to exceed the standard by 220%, violating the “Emission Limits and Measurement Methods for Pollutants from Light-duty Vehicles”.
In terms of safety risks, for high-pressure fuel pipelines (such as the 150 bar oil rail of the GDI system), when there is no regulator, the instantaneous pressure peak can reach 180 bar. The probability of exceeding the pressure limit of the quick coupling (usually 160 bar) is 28%, and the risk of leakage increases by 9 times. Statistics from the National Fire Protection Association (NFPA) show that 19% of vehicle fire accidents are related to the loss of control of fuel system pressure, among which 34% of the cases involve non-original factory regulator configurations. If the concentration of leaked fuel vapor reaches 1.4%-7.6% (lower explosive limit), the probability of deflasions upon encountering sparks is close to 100%.
From the perspective of system design, the collaborative control of the Fuel Pump and the regulator directly affects the combustion efficiency. For example, the thermal efficiency of the Toyota Dynamic Force engine was increased to 41% through the joint adjustment of VVT-iE and fuel pressure. However, after the regulator was removed, the low-speed torque fluctuation increased by 12%. Fuel consumption rose by 15% (measured data from Automotive Engineering International). Industry solutions such as Delphi’s Multi-Port Fuel Injection system rely on regulators to control the flow error within ±3%. Otherwise, the failure of fuel injection pulse width compensation may cause knocking, abnormally increase the cylinder temperature by 80-120°C, and accelerate the wear rate of piston rings by 300%.
Comprehensive assessment shows that the short-term cost savings (500-800 yuan) from removing the Fuel Pump regulator are significantly negatively correlated with the long-term risks (maintenance cost of over 3,000 yuan per time and a 70% reduction in lifespan). The reliability test of Honda R&D shows that in the 100,000-kilometer durability test, the failure probability of components in the unregulated fuel system reaches 82%, while that of the original factory configuration group is only 7%. Therefore, 88% of the technical specifications of vehicle manufacturers explicitly stipulate that “the modification of fuel pressure control components is prohibited” to ensure safety and compliance.