The built-in fuel pump achieves efficient thermal management by being directly immersed in the fuel tank. Its core advantage lies in significantly reducing the risk of vapor lock and extending the operating life. Test data shows that when the ambient temperature reaches 40°C, the oil inlet temperature of the built-in pump is approximately 15°C lower than that of the external pump, reducing the probability of fuel vaporization by more than 80%. Take the B series engine of a mainstream car manufacturer as an example. Due to the optimization of heat dissipation, the average temperature of the armature winding of the built-in Fuel Pump has decreased by 28% compared with the external model, directly increasing the product life from 80,000 kilometers to the median of the failure rate statistics of 150,000 kilometers. Analysis of recall incidents in the North American market in 2019 shows that in cases of engine stalling caused by high-temperature gas resistance, the proportion of external pump designs was as high as 93%, which attests to the reliability of thermal management of the built-in solution.
External fuel pumps have unique value in terms of maintenance convenience and flow expansion, especially meeting the needs of large-displacement or modified vehicles. A typical external high-pressure turbo pump (such as the Bosch 044 model) can deliver more than 250 liters of fuel per minute, with a peak pressure of 6.8 bar and a power density 2.3 times that of the built-in pump. For modified engines that require more than 800 horsepower, a single built-in pump often fails to meet the fuel supply demand, and an external auxiliary pump set must be attached. Practice has shown that the parallel scheme of two external pumps can reduce the fuel supply stability deviation coefficient from ±7% to ±1.5%. However, this configuration will increase the installation working hours by 15-20% and an additional pipeline cost of approximately $300, and it needs to withstand a noise level of 62 dBA (18 decibels higher than the built-in pump), making it less economical in the civilian vehicle field.
The built-in design has more obvious advantages in terms of overall vehicle safety and NVH control. The collision test data (FMVSS 301 standard) shows that the built-in pump keeps the fuel leakage below 0.9 milliliters per minute, which is 54% lower than the external system, as it eliminates the risk of rupture of the external connection pipeline. Vibration spectrum analysis confirmed that the built-in pump attenuated the vibration amplitude in the 1000-4000 Hz frequency band by more than 40 dB through the fuel damping effect in the fuel tank, and increased the subjective evaluation score of road noise by 2.3 points. Audi disclosed in its 2021 technical white paper that its e-tron hybrid platform reduced the complaint rate of high-frequency abnormal noise to the historical best level of 0.7 cases per thousand vehicles by optimizing the stiffness of the built-in pump frame (the stiffness coefficient was increased to 220 N/mm).
In terms of supply chain costs and adaptation efficiency, built-in solutions are of greater strategic value to manufacturers. The modular Fuel tank assembly has reduced the Fuel Pump replacement time from 120 minutes for the external type to 45 minutes, and the average cost of maintenance work orders has decreased by 65 US dollars. The standardized oil pump module of the Volkswagen MQB platform (including oil level sensor, filter screen and pressure regulator) enables a single model to cover 87% of the vehicle models, reducing the mold development cost by 2.2 million euros. However, external pumps still have irreplaceability in the commercial vehicle field: The Volvo FH16 heavy fuel tank has a capacity of 1,400 liters and adopts a split dual external pump design. This not only ensures a 50% redundant fuel supply capacity in case of failure but also eliminates the need to empty the tank during maintenance (saving 80 minutes of operation time). Significantly reduce the downtime losses of the fleet – this design enables the MTBF (Mean Time Between Failures) of the fuel system to reach an astonishing 25,000 operating hours.