Tech / Tech Articles

“What Size Fuel Pump Do I Need?” Your Top Tech Questions Answered!

We reached out to the guys in Summit Racing’s renowned tech department—the largest full-time staff in the industry—to identify and answer the five common tech questions they hear on a consistent basis. With help from Summit Racing’s tech advisors and other industry experts, we’ll answer those questions here at OnAllCylinders. Today’s topic: fuel pumps.

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When we refer to fuel pump size here, we’re talking about the size or amount of fuel flownot the pump’s physical size. More accurately, we’re talking about the fuel flow volume as measured in gallons-per-hour (GPH).

So here’s the real question (and it’s one of the most common questions asked of the Summit Racing tech department):

What is the optimum GPH for my engine?

There’s a simple formula to calculate GPH or LPH (liters per hour), but there are some variables to this formula, depending on your application. Norm Koval, a team leader in the Summit Racing technical department, typically follows this formula as laid out by the air/fuel experts at Holley:

Optimal GPH = (Max. HP x BSFC) / 6

Optimal LPH = (Max. HP x BSFC) / 1.585

In order to make the proper calculation, you need to determine your variables for this equation, starting with your vehicle’s maximum horsepower (Max. HP). You can determine this by having your vehicle dyno tested or by making a reasonable horsepower estimate based on the manufacturer’s advertised horsepower plus a conservative estimate of power gains made by aftermarket modifications.

The second variable in the equation is BSFC, or brake-specific fuel consumption. BSFC is a measurement of the amount of fuel consumed per unit of power produced. According to Holley, an engine typically requires .5 pounds of fuel per horsepower every hour at wide open throttle. However, this number generally applies to naturally aspirated engines.

“There are exceptions,” Koval said. “What if it’s supercharged or turbocharged? Then I might give that number a fudge factor to bump up the GPH.” If you have a highly modified, naturally aspirated engine, for example, you can tweak the BSFC number up to .55 pounds. Aeromotive recommends the following adjustments for power adders:

  • Nitrous combinations: .5 to .6 pounds
  • Forced induction engines .6 to .75 pounds

Once you’ve determined your realistic horsepower and BSFC numbers, multiply them together and divide the product by six (the typical weight of a gallon of gasoline). For example, if you have a stock engine that makes 350 horsepower, your equation will look like this:

(350HP x .5 lbs) / 6 lbs =

175 lbs/hr of fuel / 6 lbs = 29 GPH

In our example, you’d need a fuel pump that delivers 29 GPH of fuel.

A Word About Fuel Pressure

Whether you choose a mechanical fuel pump or an electric fuel pump, you’ll also need consider fuel pressure and its relationship with fuel volume. This relationship is inversely proportionalthat is, as pressure increases the volume will decrease with everything else being equal. A certain amount of fuel pressure is always required to maintain engine performance by assuring that fuel is available on demand. As engine demand goes up, as is often the case in forced induction applications, the amount of required fuel pressure will increase, causing the fuel volume to the engine to go down. Other factors and conditions, such as acceleration G-forces and friction within the fuel system itself, will also affect fuel pressure.

A basic understanding of this critical pressure/volume relationship is needed when designing the proper fuel supply system for your vehicle. You need to select a fuel pump that will meet your engine’s fuel volume AND fuel pressure demands. Many of the top fuel pump manufacturers offer charts that show fuel volume across a reasonable pressure range, so you can get the right balance for your vehicle’s fuel demands. You can also reduce sudden pressure rise and help maintain or increase fuel flow by modifying your fuel system with larger fuel injectors or other aftermarket upgrades.

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23 Comments

  1. Pingback: Fuel pump recommendations. - Ford Truck Enthusiasts Forums

  2. Mike McWhorter says:

    I have a ’99 Dodge Ram SLT LARAMIE W/ A 318 MAGNUM. I would like to know how strong is the 318 Magnum? I would love to get 400 hp/ 400 tq,is it possible?

    • OnAllCylinders says:

      Due to the airflow restriction your of your factory 2 barrel throttle body, 400hp naturally aspirated will be difficult. Supercharging may be a route for you to consider.

  3. I’m modding my mustang with headers and a high flow intake manifold and plan on making about 500 horses with a 100 shot and a tune. It’s a 5.4 dohc from a navigator. I’d like to build the engine and do a turbo later down the road. Would I be able to buy and install a 1000 horsepower capable fuel system while i’m only pushing 500 horses or do I have to get a 500 horse system and then upgrade it to a 1000 horse system after I do the turbo and build it. I’d like to only buy 1 fuel system

    • OnAllCylinders says:

      Yes, build your fuel system with a return line back to your fuel cell. That way, whatever is not used by the fuel injectors is returned back to the tank!

  4. Any guy that says he’s building an normally aspirated engine now and then is going to do a turbo later…is NEVER going to do a turbo. In fact, you’ll probably never build the engine in the first place. You don’t build an engine for 1 purpose…and then change it later thinking that somehow most of the pieces are still adequate. Clearly a noob or day dreamer wrote that…’some day I’m going to be fast’. Short answer is ‘ NEVER’

  5. Have a 351w bored .30 with a summit carb 600cfm i have a 35gph free flow pump will this be enough?

    • Yes. Even with boring it you should only be around 250 hp on th high end if you havent done anything else to it. Even in the mid 300s that would be enough.

  6. I understand the equation for GPH but id like more info on fuel pressure. Im planning on running a mild twin 60mm turbo 13 psi. Demon 750 blow through. Planning for 500 to 600 horse. Thats 75GPH AT 600. Just a good street car. Wondering what fuel pressure i should be looking at.

    • OnAllCylinders says:

      Setting your base fuel pressure at 5-7 psi (zero boost) is critical so as not to overcome the needle and seat assemblies. Then, using a boost sensitive fuel pressure regulator with a 1:1 ratio ensures that fuel pressure will rise one pound for every pound of boost from the turbos and keeping you from leaning out under boost.

  7. Pingback: Video: An Introduction to Summit Racing-Brand Universal Electric Fuel Pumps for Gas & Diesel Applications - OnAllCylinders

  8. Pingback: Express Van lift pump - Page 4 - Diesel Place : Chevrolet and GMC Diesel Truck Forums

  9. I have a 351w with a 600 cfm holley it is fitted with a regulator then filter then to the Holley the regulator is leaking so want to replace it and the filter what would you recommend?

    • Chris, thanks for your question. We’d recommend a quick call to the Summit guys at 800-230-3030. They’ll likely have a few follow-up questions to get you the right setup.

  10. I have a 351 Windsor with a 2 barrel Rochester I would like to go with a inline fuel pump but I don’t know how much fuel psi I would need. Please help. Thanksss

  11. Michael Pinar says:

    I have a built 400/425 hp 1969 351W Edlebrock Cam, Lifters, Edlebrock Intake, Edlebrock 750 Carb, Sanderson Headers….please advise me as to what Fuel Pressure Regulator and what Fuel Pump to use? Thanks

  12. I have a 72 402 fresh .30, mild cam ,hyd lifter ,alum intake,670 Holley carb, should I chnge stock fuel pump

  13. 1 have a 77 f150 with a a 466.6 that’s a 460 bord 30 over with a mid sized cam 600cfm carb high rise intake what size mechanical fuel pump do I need

  14. I have a 1982 chevy 350 g30 5.7 tioga motor home..it has a mechanical pump that has 7 psi and 40 gph…what size electric pump would I need ..will the airtex e8012s work it has 5-9 psi and 30 gph and would I need a regulator with it..
    tks

  15. Does this equation also apply with E85 applications?

  16. I have bought an 80 GPH @8 psi mechanical fuel pump.
    Does the GPH pressure remain constant or is that the max it flows?
    Q1
    Does it allow for normal functions under 80 GPH
    Q2
    Are the numbers inverse portional ex. 80 @8 =40 @4?
    Q3
    Example 350 sbc with 750- 4160 asking for fuel wot peaks at 6 psi demands 26 calculated GPH; aforementioned pump too much?

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