To make more horsepower you’ve got to stuff more air and fuel into your engine. We have the big carburetors, high flow injectors, and even complete EFI systems to make it happen, but those parts can’t do their job unless they’re supplied with enough fuel. To make sure you have the right fuel volume and pressure you have to start at the source – the fuel pump, and we have the high flow mechanical, and in-tank or external electric fuel pumps that can supply your engine with the fuel it needs.
Performance fuel pumps are generally flow rated in Gallons Per Hour (GPH) or Liters Per Hour (LPH). At wide open throttle, a naturally aspirated engine needs about 0.5 lbs. of fuel per horsepower per hour, a nitrous or forced induction engine about 0.75 lbs. of fuel per horsepower per hour. If you know your engine’s approximate horsepower, you can calculate which pump you need by multiplying the horsepower by 0.5 or 0.75, and then dividing the resulting figure by 6.2, which is the weight in pounds of a gallon of gasoline.
Using the above formula we can determine that a healthy 500 horsepower naturally aspirated street engine will need a pump that flows at least 40 GPH (500 x 0.5 = 250/6.2 = 40.32) while an 800 horsepower turbocharged track beast requires a minimum of 97 GPH (800 x 0.75 = 600/6.2 = 96.77). It’s OK to use a pump that flows more than what your engine needs, and if the difference between the required volume and pump output is great, the excess can always be returned to the tank via a pressure regulator. Never use a pump with less GPH than necessary because then your engine will be fuel starved, which can not only result in poor performance, but possible engine damage caused by a lean condition.