Q&A

Mailbag: Choosing The Right Fuel Pump Size for a Gen. III Hemi-Swapped Dodge D-Series Pickup Truck

(Image/Summit Racing)

Q. I’m planning to swap a Gen. III 5.7L Hemi with an Edelbrock supercharger into a third-gen Dodge D-Series pickup truck. My Question is about the fuel system: How do I determine what size fuel pump I need?

A. To make the proper fuel pump selection, you first need to determine your vehicle’s maximum horsepower. You can make a reasonable horsepower estimate based on the supercharger kit’s advertised power rating or an engine dyno simulation program—erring on the high side to be safe.

Calculating An Engine’s Minimum Required Fuel Flow

A fuel pump’s flow rate is determined by the amount of fuel it can supply over a given time at a specified pressure. Pumps are generally rated in gallons per hour (gph) or liters per hour (lph). The formula for calculating the minimum required flow for your application is accomplished by multiplying peak horsepower by the brake specific fuel consumption (BSFC)—a measurement that estimates fuel consumption in pounds per hour for each horsepower.

Example: A 600 hp forced induction engine with a BSFC of 0.75 would use 450 pounds of fuel per hour (600 x 0.75 = 450 lbs./hr.).

A gallon of fuel weighs approximately six pounds. To figure the gph needed, divide lbs./hr. by six (450/6 = 75 gph).

A liter of fuel weighs about 1.6 pounds. To get lph, divide lbs./hr. by 1.6 (450/1.6 = 281.25 lph).

Average BSFC Ranges

 Naturally AspiratedForced Induction
Pump Gasoline0.45 - 0.500.60 - 0.75
E850.63 - 0.700.84 - 1.05
Methanol0.90 - 1.001.20 - 1.50

***

Understanding Fuel Pressure & Flow Rate

(Graph/Summit Racing)

As pressure increases, flow rate decreases. Some pumps are rated at free flow, some at a specific psi, and others are rated in a range for carbureted or fuel injected systems.

When selecting a pump, make sure it can support the volume needed at your system’s required pressure.

General Guidelines for Fuel Pump Selection

Fuel Pump Free FlowFuel Injected EngineFuel Injected Engine
with Power Adder
30 gph/114 lph300 hp250 hp
40 gph/155 lph400 hp300 hp
50 gph/190 lph500 hp400 hp
67 gph/255 lph650 hp500 hp
90 gph/340 lph850 hp600 hp
125 gph/470 lph1,000 hp800 hp

Tags: , , , , , , ,

Leave a Reply

Your email address will not be published. Required fields are marked *

*

This site uses Akismet to reduce spam. Learn how your comment data is processed.