When the Fuel Pump flow rate exceeds 30% of the engine demand, fuel pressure can exceed the 4.5bar original factory limit, and the ECU will adjust the fuel over-supply by shortening the fuel injection pulse width (typically 2.5ms→2.1ms), causing the air-fuel ratio to shift from the theoretical 14.7:1 to 12.8:1. The combustion efficiency is decreased by 18%. For example, after Ford F-150 users changed the Fuel Pump with a flow rate of 45L/h (originally 32L/h) in 2022, the city work condition fuel consumption tested increased from 12.4L/100km to 14.9L/100km, up by 20%. U.S. test data indicates. Department of Energy demonstrates that with every 0.5bar increase of fuel pressure above the nominal, faulty fuel injectors are 15 times more likely per minute, and on average, annual fuel loss is approximately 230 liters (calculated on 20,000 kilometers).
Another cause is irregular voltage load. In one instance, the power of the enhanced Fuel Pump motor was increased from 80W to 120W, leading to an additional 40% generator load boost. This pushed the engine idle speed to increase by 150rpm to maintain the power balance, indirectly raising the idle fuel consumption from 0.8L/h to 1.1L/h. It can be seen from the 2023 report of Bosch Research Institute that when the operating current of the fuel pump exceeds 25% of the initial design value, the compensation power supply will be triggered by the vehicle’s on-board power management system, reducing the efficiency of the vehicle’s circuit from 92% to 85%, corresponding to an additional consumption of 0.3kWh electricity for every 100 kilometers (equivalent to 0.1L fuel). The first trial version of Tesla Cybertruck increased the charging frequency of the 12V battery by 30% due to the high-flow Fuel Pump, leading to a 5 percentage point drop in regenerative braking energy recovery efficiency.
Fuel temperature control loss has aggravated the energy consumption problem. An example of a certain modification shop shows that after installing the Fuel Pump with the flow rate of 55L/h, due to the radical increase in the amount of the returned fuel, the fuel circulation rate became three times greater. The temperature of the fuel within the fuel tank rose from 35°C to 48°C, and the fuel density decreased by 1.2%, which forced the ECU to increase the reference value of the fuel injection amount by 2.3%. SAE research shows that for every 10°C increase in fuel temperature, the atomized particle size increases by 8μm, the burning speed decreases by 12%, the emission of unburned hydrocarbons increases by 18%, and the corresponding fuel consumption rises by approximately 4.7%. During Porsche 911 GT3 Nurburgring test, due to the long-term high-load working of the track model Fuel Pump causing fuel vaporization, the fuel consumption rate increased dramatically by 27% during the later period of the lap time.
Some upgrading plans can realize the optimization of fuel consumption through the coordination of systems. For example, when the owner of the Toyota GR Supra replaced the Fuel Pump with a 40L/h flow rate, he also replaced the fuel injector with an orifice 0.2mm larger and the pressure regulating valve with a response time of less than 5ms. Finally, they managed to achieve a 3% increase in combustion efficiency and a fuel economy of 0.6L/100km. Industrial statistics indicate that if the fuel pump flow rate and the turbocharger boost value are matched at a ratio of 1:0.8 (e.g., a flow rate of 50L/h is matched with a boost value of 2.5bar), the fuel economy can be enhanced by 12% in contrast to blind modification. Magna International’s smart Fuel Pump system launched in 2024 was able to reduce fuel consumption by 4.2% under WLTC conditions by adjusting the flow rate by ±15% in real time. However, the retrofit cost was up to three times the cost of the original factory pump (approximately 800 US dollars).
Authoritative tests have proven that a Fuel Pump upgrade with no professional tuning has a 76% likelihood of leading to heightened fuel usage. EPA test data on 200 modified vehicles show that for vehicles in which the fuel pump flow exceeds the ECU calibration range by more than 20%, the average cost of fuel over three years is raised by $3,200 (based on 15,000 miles per year and an oil price of $3.5 per gallon). Users are recommended to use OBD-II to monitor the long-term Fuel correction value (LTFT) over the long term. In case it’s over ±10% all the time, the fuel system parameters should be re-matched, as otherwise, it will trigger a vicious cycle – one example on the Ford Ecoboost engine shows that Fuel Pump upgrade with no correction done has increased the rate of oxygen sensor poisoning by 40%. The attenuation rate of the catalytic converter’s efficiency is 2 times greater, and the total maintenance expense can be 4.8 times the expense of the original factory setup.