IGNITION, FUEL SYSTEMS AND ELECTRICAL PROPERLY SELECTING ELECTRONIC FUEL INJECTION COMPONENTS (continued...) To determine the overall capacity of a fuel pump rated in liters per hour (L/hr), use the following additional conversions: Do: To Get: (L/hr)/3.785 a160 US gallons/hr Multiply above by 6.009 lb/gallon a160 lb/hr Multiply above by 0.9 a160 Capacity in lb/hr at 90% Divide above by BSFC a160 “Horsepower Capacity” (flywheel) So, for a fuel pump rated at 110 L/hr for example, supplying a naturally aspirated engine: 110/3.785 = 29.06 U.S. gallons/hr 29.06 x 6.009 = 174.62 lb/hr 174.62 x 0.90 = 157 lb/hr @ 90% Capacity 157/0.50 = 314 hp safe naturally aspirated “Horsepower Capacity” Safe “Horsepower Capacity” @ 40 psi with 12 V assuming 0.5 lb/hp-hr BSFC 60 L/hr pump = 95 lb/hr x 0.90 = 86 lb/hr, safe for up to 170 naturally aspirated flywheel hp 88 L/hr pump = 140 lb/hr x 0.90 = 126 lb/hr, safe for up to 250 naturally aspirated flywheel hp 110 L/hr pump = 175 lb/hr x 0.90 = 157 lb/hr, safe for up to 310 naturally aspirated flywheel hp 155 L/hr pump = 246 lb/hr x 0.90 = 221 lb/hr, safe for up to 440 naturally aspirated flywheel hp 190 L/hr pump = 302 lb/hr x 0.90 = 271 lb/hr, safe for up to 540 naturally aspirated flywheel hp 255 L/hr pump = 405 lb/hr x 0.90 = 364 lb/hr, safe for up to 720 naturally aspirated flywheel hp Very Important Note: For any type of forced-induction engine, the above maximum power levels will be reduced because as the boost pressure increases, the fuel pressure required from the pump also increases, creating an additional load to the fuel pump, which results in a decreased fuel flow rate at the higher pressure. In order to do proper fuel pump sizing for these applications, a fuel pump map is required, which shows flow rate versus delivery pressure for a given voltage. For example, a 255 L/hr pump at 40 psi may only supply 200 L/hr at 58 psi (40 psi plus 18 lbs of boost). Additionally, if you use a fuel supply line that is not large enough, this can result in decreased fuel flow due to the pressure drop. For example, 255 L/hr at the pump may only result in 220 L/hr at the fuel rail because as the required pressure increases (due to the pressure loss from the supply line restriction), the maximum flow rate of the pump decreases. Figure 1 shows an example fuel pump map for a pump assembly at a supply voltage of 13 V. Fuel Flow vs Pressure @ 13 V supply M-9407-GT05T05G-7049-M 430 380 330 ) h Single Gen6 Pump p ( Twin Gen6 Pumps w l F 280 230 180 250 300 350 400 450 500 550 600 P res s ure (kP a) Figure 1 MEASURING FUEL PRESSURE The above fuel pump sizing information should be regarded as a guideline in selecting the size of pump you need. Once installed in the car, you still need to verify that adequate fuel pressure (at least 39.15 psi across the injector) is maintained at all engine speeds and loads. Do not skip this fuel pressure verification step, as failure to maintain adequate fuel pressure can cause issues ranging from calibration difficulty to engine failure due to running lean. For important information about the proper usage of performance parts, please see page 14. 214 Techline (800) FORD788 See pages 286-292 for important safety, emissions and warranty information.
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