The influence of fuel atomization quality on combustion efficiency has been quantified by a large amount of experimental data. According to a research report released by SAE International, when the average diameter of oil droplet Sottel (SMD) deteriorates from the ideal 20μm to 150μm, the combustion duration is correspondingly extended by 5.5ms – this is equivalent to missing 17% of the crankshaft Angle window during the combustion process at 6000rpm. In 2019, Bosch confirmed through high-speed photography technology that in direct injection systems, poor atomization leads to a 40% decrease in flame propagation speed, directly causing a 22% reduction in output torque in the high-speed range (above 5000rpm). What is more serious is that the incompletely evaporated fuel film can induce pre-ignition, causing the signal strength of the knock sensor to suddenly increase by 3.6G, forcing the ECU to reduce the ignition advance Angle by 15 degrees and further compress the available speed boundary.
There is a strong correlation between the pressure parameters of the Fuel Pump system and the atomization effect. The working pressure of modern high-pressure fuel pumps is usually set at 350bar (such as the Volkswagen TSI model). When the pressure fluctuation range exceeds ±25bar, the fuel injector flow deviation will reach 4.8%. Delphi’s bench test shows that if the system pressure drops to 280bar, the median diameter of the fuel droplets sprayed increases from 22μm to 45μm, causing the indicated thermal efficiency at the 8000rpm operating point to drop from 34.2% to 29.1%. In 2021, Honda recalled 430,000 vehicles due to a design defect in the low-pressure fuel pump. This fault caused the peak fuel pressure to drop by 32%. Owners complained that when the engine speed exceeded 3,000 RPM, the engine power dropped sharply by 40%, and the maximum speed was strictly limited to below 4,500 RPM.
The engine’s speed climbing ability is exponentially related to the oil-gas mixing rate. Dynamic tests by German FEV Power Company show that during the acceleration process from idle speed to the red line speed, the ideal atomization state should maintain the air-fuel ratio fluctuation range of ±0.8, while under poor atomization conditions, this deviation expands to ±2.5. In a rapid acceleration test of a 2.0T engine with a speed gradient of 500rpm/ms, the combustion failure rate caused by the delayed evaporation of fuel droplets reached 12.3%, forcing the electronic throttle opening to be reduced by 28% for torque intervention. Track data analysis of the Porsche 911 GT3 reveals that when the fuel filter is clogged and the fuel supply pressure drops by 15%, the vehicle’s acceleration time in the 7000-9000 RPM range is extended by 1.2 seconds, equivalent to a 3.7% loss in lap time.
The aerodynamic effect intensifies the atomization influence as the rotational speed increases. Wind tunnel tests at the Cummins Technology Center have confirmed that the intake manifold airflow velocity is approximately 35m/s at 3000rpm and can reach 82m/s at 6000rpm. When the diameter of the oil droplet is greater than 50μm, the Weber number (We) drops below the critical value of 5, resulting in the fuel being unable to break effectively. This effect caused the oil-gas mixture uniformity index in the cylinder of a certain 1.5L naturally aspirated engine to deteriorate from 0.92 to 0.78 at 5000rpm, and the probability of the instability of the air-fuel ratio control triggering the ECU deceleration protection increased by 17 times. In the 2018 WRC race, the Hyundai team’s high-pressure Fuel Pump wore out, causing the fuel particle size to exceed the standard. As a result, the speed limit of the racing car was forcibly locked at 5,500 RPM on the gravel section, resulting in a loss of approximately 11% of the climbing performance.
The solution requires collaborative optimization among multiple systems. The Toyota TNGA architecture controls the tolerance zone within ±0.25ms in the Fuel injector design, and in combination with the 350bar Fuel Pump, ensures that the SMD across the entire speed range is ≤25μm. The BMW Valvetronic system controls the intake flow rate through variable valve lift, maintaining the turbulent kinetic energy density within the golden range of 12-18m²/s³ in the 2000-7000 RPM range, thereby reducing the air-gas mixing time to 0.8ms. Real vehicle test data shows that this type of integrated solution can expand the effective speed bandwidth of the engine by 18% and increase the torque output in the red line speed range by 15%. For car owners, the cost of regularly replacing fuel filters (every 40,000 kilometers) and monitoring fuel pressure (deviation ≤5%) only accounts for 3.2% of the maintenance budget, yet it can avoid the risk of power loss caused by limited engine speed.