Fuel On Demand: High Performance Variable Speed Fuel Pumps

Internal combustion engines require sufficient amounts of fuel to make power. This isn’t just about making power, but preventing self-destruction because we don’t have enough fuel in its important relationship with air. Nitrous, supercharging, and turbocharging create demand to where you must have enough fuel to air to prevent engine damage, yet not overwhelm the engine and lose power.

Imagine a system where you can fine-tune fuel delivery to your engine’s demands. Fuelab, Aeromotive, and Holley have precisely what the doctor ordered for your tough fuel system requirements. You may opt for a variable speed fuel pump system from Fuelab, go with a pressure-regulated conventional high-capacity pump system from Holley, or utilize an adjustable controller for your pump from Aeromotive. The choice is yours.

Choosing A System

Before you can properly select a fuel pump, it’s important to know what kind of power your engine is going to make plus how it will be used most of the time. “In the past, fuel pump manufacturers have rated their offerings based on gallons-per-hour, free-flow (no test pressure), and with no reference to test voltage,” Jesse Powell of Aeromotive tells us. “In the real world, this gave no indication of the horsepower that could be supported by such a pump.” This is why you need to know as much about your engine as is possible before choosing a pump system. We say “pump system” because fuel delivery happens via more elements than just a pump. There’s high-pressure fuel line and a means of regulating fuel pressure. Most systems employ a pressure regulator, which controls return flow to the tank thereby controlling fuel pressure. The pressure regulator gets its vacuum signal from intake manifold vacuum, which is based on throttle position and load.

Fuel delivery and pressure come from an electric fuel pump. An adjustable fuel pressure regulator controls return flow to the tank, which controls fuel system pressure. Intake manifold vacuum is applied to the regulator based on throttle position and engine load.

Powell tells us pump size is determined by how much horsepower your engine is expected to make and how much fuel will be required to support that power. You must also consider power adders like nitrous and supercharging in your plan. Aeromotive suggests estimating on the high side when it comes to horsepower to play it safe. Better too much fuel than too little. Too little means lean mixture, detonation, and great potential for engine failure.

In the past, manufacturers have rated their offerings based on gallons-per-hour, free-flow with no reference to voltage. This gave no indication of the horsepower that could be supported. – Jesse Powell, Aeromotive

BSFC (Brake Specific Fuel Consumption) is crucial to fuel pump and injector selection – so get familiar with this term and what it means. BSFC boils down to how much fuel we’re going to burn to make a given amount of horsepower. The higher the BSFC number, the more fuel we’re going to have to have.

Aeromotive adds that naturally aspirated engines are most efficient with a BSFC between .4 and .5 lbs/hp/hr.

Nitrous combinations call for additional fuel and often develop a BSFC from .5 to .6 lbs/hp/hr. If you’re going to supercharge or turbocharge, BSFC should range from .6 to .75 lbs/hp/hr. This means you need greater amounts of fuel to meet the demand.

So what does all this complicated math mean for you?

Here are a couple of real world examples:

If we have a 650 horsepower engine and multiply horsepower times .4 BSFC, we’re going to burn 260 pounds of gasoline. If we have .75 BSFC, our 650-horse engine becomes very thirsty at 487 pounds of gasoline. This means .75 BSFC is grossly inefficient. Same horsepower, but with huge amounts of fuel consumption. This means you must carefully choose the right pump system for your engine’s demands.

Avoiding Engine Armageddon

How Do I Know How Much Pump I Need?

  • Engine Flywheel Horsepower
  • Engine fuel efficiency, commonly referred to as BSFC or Brake Specific Fuel Consumption
  • Maximum fuel system pressure and the pump’s flow volume at that pressure
  • Available voltage at the fuel pump under engine load and the pump’s flow volume at that voltage

Here’s what you’re going to need to know about choosing injector size: Take the known amount of gasoline required in pounds and divide by the number of injectors you’re going to need. Again, err to the side of caution. Too much is better than too little. Aeromotive suggests the following formula: take 650 horsepower and multiply by .4 BSFC to get 260 pounds of fuel. Then, take 260 pounds of petrol and divide by eight injectors to get 32.5 lbs/hr or 33 lb/hr injectors. When we take that 33 lb/hr figure and crank in caution with 33 divided by .8, we get 41 lb/hr at an 80-percent duty cycle. And because you care about your engine, it’s a good idea to check these numbers with a seasoned engine builder before buying fuel system components.

Fuelab’s On-Demand Fuel Delivery System

How cool is this? Fuelab introduces the first true on-demand fuel delivery system -- a variable speed fuel pump system where speed is based on demand. Calm on the street and all hell breaking loose when it's time to pin the butterflies.

Fuelab is a forward thinking company with digital electric fuel pumps. Your first thoughts are likely how does anyone digitize an electric fuel pump? Fuelab does this via electronic control where fuel pump speed is regulated based on engine power demands.

We decided to introduce new brushless pump motor technology into fuel pump design and manufacturing. – Brian Paitz, Fuelab

“We decided to introduce new brushless pump motor technology into fuel pump design and manufacturing,” Brian Paitz of Fuelab tells us.

Fuelab claims that brushless technology enables them to make a lighter pump that offers a quicker response to changing power demands. What’s more, you can run just about anything through the Fuelab pump — gasoline, methanol, E85, or diesel. And, you can change fuel type at any time.

“One problem with a high-performance electric pump like this is heat,” Paitz comments. “These pumps require a lot of electric current, which makes heat; and heat causes unwanted vapor lock.” Vapor lock causes fuel stagnation shutting an engine down in short order,” he adds. “To prevent vapor lock, Fuelab has developed an electronic fuel pressure regulator that reduces heat when a vehicle is on the street.” This process reduces pump speed generating less heat. The pump runs at a conservative speed on the street where large quantities of fuel are not needed. When it’s time to lock and load, the Fuelab system kicks into high gear providing plenty of fuel to meet the increased demand. Speed control is based on feedback from the pressure regulator. “It is the first true on-demand type of fuel system,” Paitz adds.

Fuelab Options


Few companies are more on top of the fuel game than Holley. Known for legendary carburetors so loved by racers worldwide, it’s no surprise that our friends at Holley have come up with a high-performance fuel delivery system for fuel injected and carbureted systems alike. The in-line Holley HP billet fuel pump is just what the doctor ordered for carbureted and fuel injected vehicles alike. Liz Miles, respected automotive journalist and Holley representative, told us, “The HP line of billet electric fuel pumps feature Gerotor technology for positive displacement providing reliable fuel delivery on the street or on the track.” She adds the HP pump can deliver for 100,000 miles from a good-looking, cost effective package. It can take up to 18.5 volts and deliver up to 80 psi.

If you’re going to huff serious horsepower, Holley’s patented twin-pump Dominator is for you. The Dominator, as its name implies, is excellent for nitrous, supercharging, or turbocharging. This guy is machined from solid billet for fierce durability. It’s also fully submersible for in-tank use or you can mount it on the chassis for in-line use. This pump can be triggered from a myriad of sources to bring that additional fuel on demand that your engine requires at wide open throttle.

Holley's new line of HP billet electric fuel pumps offer solid durability -- 80 psi maximum and 18.5 volts. And they can do this for at least 100,000 miles.

Holley Pump Facts

Aeromotive’s Fuel Pump Controller

What if you’d like to continue using the fuel pump that you already own, but want the benefits that a variable speed pump offers? That’s exactly the option that Aeromotive brought to the table with the creation of their Billet Fuel Pump Speed Controller. The device, when used on any pump on any type of vehicle, reduces fuel heating and vapor-lock issues by matching the duty cycle of the fuel pump to the engine RPM. When at low demand, the controller slows down the speed of the fuel pump to reduce suction side cavitation and vapor lock. As demand increases, the controller then returns the pump to 100% duty cycle to achieve maximum flow.

The Billet Fuel Pump Speed Controller operates by emitting a pulse modulation signal to the pump motor to reduce or increase the pump speed. Such an operation, that doesn’t alter/reduce voltage, is virtually harmless to the pump motor.

The Billet Fuel Pump Speed Controller features LED indicators to confirm ignition signal hookup and verifies action of the manual override circuit, as well as when the circuit is providing full voltage to the pump. Other features include a billet 6061-T651 aircraft aluminum housing with a black anodized finish, a solid-state transistor circuit rated at 40 amps, and an adjustable, full-speed RPM threshold.

The Fuel Pump Future is in your hands

Regardless of which of these routes you opt to take for your fuel system needs, the benefits of a variable speed fuel system are aplenty, and there’s no question that your engine will benefit in the long-term from variable speed operation. Just when you thought selecting the proper pump for you needs was a tricky element, modern technology went and dropped another decision into your lap, but technology’s great, isn’t it?

Article Sources

About the author

Jim Smart

Jim Smart cut his teeth on automobiles in the 1970s with a passionate interest in Ford and Chrysler musclecars. After serving in the United States Air Force, he transitioned into automotive journalism as editor of Mustang Monthly magazine in 1984. In 1990, Jim joined Petersen Publishing Company as a feature editor at Car Craft, and later as editor of Mustang & Fords, then senior editor at both Mustang Monthly and Mustang & Fords. Jim writes for a wide variety of automotive publishers and websites.
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