Replacing the high-performance Fuel Pump also significantly improves the throttle response speed. Experimental data show that when the fuel pressure recovers from the aged 240 kPa to the original factory standard 400 kPa, the synchronization delay between the throttle opening signal and the fuel injection pulse width can be improved from 320 milliseconds to 90 milliseconds. For instance, BMW’s 2022 TSB 12-340 technical notice on the N55 engine re-emphasized that after fuel pump upgrading (increasing the delivery from 130L/h to 180L/h), the 0-60 mph time fell by 0.6 seconds and the turbocharger’s starting speed was increased by 22%. A comparative test by third-party testing firm SAE International indicates that in the Walbro 450 series high-flow Fuel Pump-equipped vehicles, in WOT (wide-open throttle) mode, the fuel rail pressure fluctuation range is lowered from ±15% to ±3%, and air-fuel ratio control precision is improved by 40%. Therefore, the frequency of torque limit due to insufficient fuel supply in the ECU is reduced.
The degradation of the performance of the stock factory fuel pump is a potential cause of throttle lag. The engine engineering data of the Ford Ecoboost 2.3T engine shows that when the motor speed of the fuel pump degrades from the desired 7200 RPM to 5200 RPM, the flow of the fuel supply will be decreased by 28%. This causes a highly reduced fuel pressure when the throttle opening is over 50% (from 380 kPa to 260 kPa). These problems are located up to as high as 34% on vehicles with mileage over 100,000 kilometers (J.D. Power 2023 Powertrain Reliability Report). After replacement of the new Fuel Pump, oil pressure build-up time can be decreased from 2.1 seconds under cold start to 0.8 seconds, effectively removing turbo lag. In certain cases, in 2021, Volkswagen released an improved fuel pump (Part number 06E127025K) for the EA888 Gen3 engine. By enhancing the geometry of the impeller, it increased the maximum fuel supply pressure from 5.8 Bar to 6.5 Bar, thereby enhancing the torque response speed within the range of 2000-4000 rpm by 18%.
The application of High-flow Fuel Pump in the modification market has been effective. Hondata test data shows the Honda Civic Type R (FK8) with the Si Trim fuel pump can maintain a fuel pressure of more than 4.2 Bar in the high-rpm zone of 6500 rpm (stock pump pressure decreases to 3.5 Bar). Under the combined use of the ECU calibration, the throttle response lag is reduced by 150 milliseconds. The comparative test experiments by Bosch auto after-sales department show that under the same conditions, employing the newest two-stage variable displacement Fuel Pump (e.g., Bosch model 040), at throttle opening ranging from 20%-80%, fuel flow control speed is 3.2 times greater than that of traditional single-stage pump, and oscillation range of air-fuel ratio at transient operating conditions is decreased from ±1.2 AFR to ±0.4 AFR.
There is a clear connection between the overall cost of replacing the Fuel Pump (parts 200-600+ labor cost 150-300) and the performance increase based on economic analysis. A 2023 study by the University of Michigan’s Department of Mechanical Engineering indicates that for turbocharged cars, the return on investment in fuel system upgrades can reach up to 1:1.3 (i.e., 1.3 horsepower output for each 1 horsepower input), while for naturally aspirated cars, it is 1:0.8. Preventive maintenance data indicate that replacement of the Fuel filter every 80,000 kilometers (cost $50-$120) can extend the life of the Fuel Pump to 150,000 kilometers and maintain the fuel supply flow attenuation rate below 5% per year (SAE J2638 Society of Automotive Engineers standard). Actual test data from Chevrolet Camaro SS owners indicate that the transition time from 75% throttle opening to full opening upon upgrading to the DSX fuel pump package dropped from 0.45 seconds to 0.28 seconds, and the fuel pressure curve standard deviation is lowered from 12.4 kPa to 4.7 kPa.