The basic differences between the high-pressure and low-pressure Fuel pumps are the working pressure range and associated applications. According to SAE J2719, the low-pressure fuel pump has a typical pressure output of 2.5-4 bar, with 150-300 L/h (liters per hour) flow rate range, and is suitable for naturally aspirated engines. The working pressure of high-pressure fuel pumps (such as the Bosch HDP 5 series) may be up to 4-7 bar, and the maximum flow rate is 600 L/h. They are specially meant for direct injection (GDI) and turbocharging applications. For instance, in the 2023 24 Hours of Le Mans endurance race, the 2.0L V4 engine of the Porsche 919 Hybrid racing car featured a high-pressure Fuel Pump. At 7 bar pressure, it achieved a fuel atomization particle size of ≤20 μm (50 μm for the low-pressure pump), improved combustion efficiency by 9%, and reduced fuel consumption per lap by 1.2 liters.
It is very different in the choice of materials and manufacturing costs. Low-pressure fuel pumps essentially adopt nylon casings and plain steel impellers, with a unit price of around 80-150 US dollars and an average life expectancy of 50,000 kilometers. The high-pressure pump needs to utilize a stainless steel casing and ceramic bearings in order to withstand mechanical stress of 10-15 MPa. The unit price is raised to 250-600 US dollars but the life expectancy is raised to 150,000 kilometers. Toyota’s 2024 technical white paper states that the high-pressure Fuel Pump of its Dynamic Force engine fails only 0.3 times per thousand units, a 75% decrease compared to the previous generation of low-pressure pumps (1.2 times per thousand units). Under the severe conditions of the Dakar Rally, the risk of clogging of the low-pressure pump is as high as 18% when the dust concentration is 200 mg/m³, while the risk of the high-pressure pump is compressed to 2% due to the precise filtration system (5 μ m-level filter screen).
The contrast between energy consumption and thermal management characteristics is dramatic. Low-pressure fuel pumps’ motor power is typically 40-60W, and the highest tolerance of fuel temperature is 85°C. The motor power of high-pressure pump is as high as 120-180W, and it has an active cooling system, which can be run stably at a fuel temperature of 120°C. Under the environmental test of Volvo Polestar 2’s 350 bar high-pressure Fuel Pump between -30°C and 140°C, the flow fluctuation rate was only ±1.5%, and the same-level low-pressure pump’s flow rate was decreased by up to 25% during low-temperature start. In accordance with a 2023 study in Automotive Engineering, the precision of fuel pressure control by the high-pressure pump (±0.1 bar) is five times higher than that of the low-pressure pump (±0.5 bar), reducing nitrogen oxide emissions by 14% from the Volkswagen EA888 engine.
The complexity of maintenance directly influences the cost of use. The standard replacement time for low-pressure fuel pumps is 5 years or 80,000 kilometers, and the onetime maintenance price is in the range of 200 to 400 US dollars. Since pressure sensors and ECUs are incorporated in high-pressure pumps, their maintenance price has risen to $500-$1,200, but the unplanned downtime rate can be reduced from 12% to 0.8% by real-time fault diagnosis. For instance, the high-pressure Fuel Pump installed in the Ford F-150 Raptor R features self-cleaning. It removes sediment on the filter screen automatically at every 1,000 kilometers, raising maintenance frequency under desert driving conditions from monthly to quarterly and saving an average annual maintenance cost of around $1,800.
The trend of intelligence intensifies technology differentiation. Bosch’s latest high-pressure Fuel Pump (HDP 7 series) has a pressure-flow closed-loop control algorithm, reducing the response time to 0.02 seconds. In the transient modes of operation of WRC racing cars, the fuel supply error rate is as low as 0.3%. In contrast, low-pressure pumps retain mechanical regulating valves, and the error rate reaches as high as 3.5%. Delphi’s 2024 market forecast predicts that in 2028 the penetration of new energy hybrid models’ high-pressure fuel pump will be at 74%, and their modularity can reduce production costs by 28% from the current level, resulting in the market share of low-pressure pumps focusing in this civilian commuter vehicle market space (≤26%).