If the Fuel system originally developed by the ATV is modified to a Fuel Pump having a flow of 20L/h and 3.5bar pressure and a high-efficiency pump of 30L/h flow and 5bar pressure after being modified, it could lead to the fuel supply being beyond the ECU regulation range (±10%), making the air-fuel ratio go out of balance. For instance, in 2021, users of the Polaris Sportsman 850 substituted the Fuel Pump with one that had a redundant flow rate. The fuel injection pulse width, which was measured, was 15% shorter, which resulted in an 8% rise in combustion chamber temperature and a 30% rise in the probability of knocking. In the end, the piston ring wear life reduced from 100,000 kilometers to 60,000 kilometers. Industry research shows that with the fuel pump flow exceeding engine demand by 50%, fuel pressure fluctuation range can achieve ±0.8bar, leading the ECU to adjust the fuel injection parameters constantly. In the short term, fuel consumption may increase by 12% to 18%, while in the long term, it will accelerate oxygen sensor breakdown (reducing its life expectancy from 80,000 kilometers to 40,000 kilometers).
From the economic perspective, a Yamaha Grizzly 700 consumer replaced the Fuel Pump with a flow rate of 35L/h (40% higher than the original factory price). However, due to the reduced fuel efficiency, the cost of fuel increased by approximately 1,200 yuan annually. Moreover, due to the damage caused by overloading to the fuel injector, there was an additional maintenance cost of 3,000 yuan. The Return on Investment (ROI) is -65%. According to the SAE 2023 report, when the ATV fuel system compatibility error is 20% above the design value, it will reduce the fuel filter element clogging cycle by 60% (15,000 kilometers from the factory origin vs. After modification for 6,000 kilometers), while at the same time, the fuel temperature in the fuel tank rises by 10°C due to rapid circulation, which may enhance the risk of vapor lock (25% increased likelihood).
From physical conditions, when a specific Briggs & Stratton Fuel Pump (nominal flow rate of 28L/h) was installed on the State Warrior 500, since the size of the pump body was 15% larger than the original position, the bending radius of the fuel pipeline was less than 70% of the normal value, and the locally increased fuel flow rate increased sharply by 3m/s. The wear rate of the pipe wall increased by 200%. More critically, in a case where the fuel pump’s power was increased from 12W to 18W, the generator load rate increased from 55% to 85%, and the battery cycle life decreased from 5 years to 2.8 years. Industrial test data shows that if the fuel pump working pressure is increased by 30% above the original factory level, the rate of fuel injector seal failure increases by 45%, and fuel vapor emission is 2.3 times that of the EU Stage V regulation.
From a perspective of safety levels, during the 2022 Fuel leakage incidents due to unauthorized modification of the Honda TRX420’s Fuel Pump, its leakage rate was as much as 0.8L/min (far beyond the safety level of 0.2L/min), and the probability of fire after hitting the heat-exhaust pipe was 92%. Statistics by the United States ATV Safety Committee show that mechanical failure crashes due to fuel system compatibility problems account for 34% of such crashes, and 75% of them are caused by fuel pump parameter mismatch. It is recommended that the users refer to the ISO 9001:2015 standard, verify the output of the fuel pump using a laser flowmeter (the difference should be <±3%), as well as monitor the long-term air-fuel ratio variation in combination with OBD-II data (normal range 14.6:1±0.3).
Authoritative bodies such as the American Petroleum Institute (API) suggest that in the process of choosing a Fuel Pump, one should ensure that the flow rate matches the engine’s peak power (formula: Flow rate L/h= Power kW×0.55). As an example, a 90kW ATV translates to a flow rate of 49.5L/h. If the user still wants to use a high-flow pump, upgrading the fuel pressure regulating valve (response speed <5ms) at the same time, enlarging the nozzle aperture (at least 0.15mm), and reinforcing the cooling system (the fuel temperature must be controlled to 45°C±5°C) are required. Yamaha’s own statistics show that compliant modifications can increase the fuel system reliability from 72% to 96%, but the modification cost will generally be over 18% of the cost of the original vehicle, and the necessity should be carefully evaluated.