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Already common in many industrial and lifestyle applications, brushless DC motors can now be found in hot rodders’ fuel tanks. Brushless motors have been widespread in cordless power tools and radio-controlled vehicles for some time—in addition to commercial HVAC systems and the aerospace industry. However, their popularity in the performance aftermarket is just starting to grow with increasing use in cooling-fan motors, electric water pumps and electric fuel pumps.
“There are benefits and drawbacks to brushless technology,” says Holley engineer Matt Sosa. “The main drawback is that they’re expensive when compared to a brush motor, and they need a separate controller.”
Holley’s brushless line is anchored by the VR1 fuel pump, which can be ordered in a number of configurations. Built with a powerful yet efficient twin-screw rotor design, this pump is available in both in-tank and external mount configurations. The VR2 line is a paired set of VR1s that can provide enough fuel volume and pressure for 4,400-horsepower in EFI applications.
“The VR2 allows some cool options. You can run both pumps at half speed, or one at full speed and the other at half,” says Sosa. “It allows you a broad range of flow because each motor is controlled individually.”
The pumps (seen here in a 12-149 drop-in EFI fuel pump assembly) are built for continuous duty.
A simple brushed DC motor—the type many long-time performance enthusiasts grew up with when building slot cars and currently the foundation for most aftermarket electric fuel pumps—is constructed of five components: stator, coil, rotor, commutator and brush. The stator is basically a fixed magnetic field with opposite polarity, or commonly known as north and south poles. This could be two or more permanent magnets inside a housing.
The rotor rotates on an axis inside the stator and is comprised of electromagnetic coils (the rotor and coil combination is also called an armature) that are energized when an electric current is passed through the brushes on to a commutator that is wired to the coils.
The stator and brushes do not move. The commutator is a split-ring component on the motor’s shaft and contacts the brushes—which are connected to opposite poles of the DC power source. The turning action of the motor is the result of interaction between the permanent magnets in the stator and the electromagnets on the rotor. They follow the laws of physics that hold opposite poles attract and like poles repel away from each other.
Basically, when the coils are energized, they are pushed away from a like magnetic pole in the stator and then pulled towards the opposite pole of the next magnet. In order to keep the motor running, the current must be reversed continuously to change the polarity of the coils. In other words, the coils must keep “chasing” the polarity of the next magnet. That’s the duty of the brushes and commutator.
The Holley BLDC (Brushless DC Controller) is designed to operate either as a stand-alone controller or to be used as a slave device via a ground input. The BLDC can also be incorporated into the Holley EFI System. VR1 pumps use one controller, VR2 pumps utilize two controllers.
There are numerous DC brush motors in a production vehicle, including the HVAC fan, power windows and power seats. They’re simple and inexpensive to produce. However, the brushes and commutators can wear out which can require maintenance and possibly repair costs.
With a brushless motor, the stator and rotor are reversed. The permanent magnets are now located on the motor’s shaft and the electromagnetic coils are fixed and surround the shaft. The previous duties of the brushes and commutator are replaced with a controller that coordinates the electric current to the coil windings.
To start the motor or change the speed, the controller adjusts the voltage to the coils. The dynamics of the motor is the same as a brush motor with the coils changing polarity and chasing the opposite pole on the permanent magnets.
This is a closed-loop operation requiring a sensor to tell the controller the position of the coils. Then the controller can phase the current appropriately. As you can see, brushless motors have no sliding elements in their construction, which can be a big benefit in applications where sparks and friction noise in a brushed motor could be a cause for concern. Finally, with fewer moving parts, the reliability factor of a brushless motor increases over a brushed version.
The VR1 series pump (foreground) is capable of supporting up to 2150 horsepower in an EFI form or 2,400 horsepower in a carbureted form. The VR2 series pump can support up to 4,400 horsepower (EFI) or up to 4,800 horsepower (carbureted). Both pumps are compatible with pump gas, race gas, E85 and methanol fuels.
“We’re really talking about the benefits of a brushless motor attached to the pumping assembly,” says Sosa. “The twin-screw pump looks like a mini supercharger and is one of the reasons the engineering team was able to get the higher volumes out of the system. You combine a torquey motor and innovative twin-screw pumping assembly.”
The VR1 is rated at 162 gallons per hour (gph) at 8 psi, 138 gph at 43 psi, 126 gph at 60 psi and 87 gph at 130 psi.
The VR2 is rated at 323 gph at 8 psi, 276 276 gph at 43 psi, 254 gph at 60 psi and 169 gph at 130 psi. All the ratings are at 13.8 volts and using gasoline.
“These pumps can be run up to 18.5 volts, and the flow numbers will increase with the voltage,” says Sosa. “Another benefit of a brushless pump is its efficiency. A VR pump will flow more while drawing less amperage than a comparable flowing brushed pump.”
Holley notes that a VR running at 60 psi and 13.5 volts will draw approximately nine amps, resulting in a flow of around 14 gallons per amp. A competitor under similar conditions will flow 5.9 gallons per amp.
“That makes the VR about 240 percent more efficient at converting electrical power into useful work,” says Sosa. “This is a big deal in its own right but particularly for drag racing or other disciplines where racers don’t run alternators because keeping the electrical load down is a necessity. Even those running alternators need to keep the pump draw down, so that there is more power available to support other electrical load items. An efficient fuel pump can be the difference between needing a new high-capacity alternator or not.”
The VR1 will support naturally aspirated engines from 1,500 up to 2,400 horsepower, while forced-induction engines are limited to 1,000 up to 1,800 horsepower—all depending on the flow settings. With the VR2, the numbers jump to 3,000 to 4,800 for naturally aspirated and 2,300 to 3,600 horsepower with forced induction. Again, the max horsepower numbers are predicated on the flow settings. Both the VR1 and VR2 are compatible with pump gas, race gas, methanol and E85.
“Racers using E85 and methanol, those are the guys who really need that kind of flow,” says Sosa, adding that Holley suggests draining and flushing the fuel system after each race event when using alcohol fuels. “High flow numbers are maintained out to higher pressures. That’s of particular interest for boosted racers.”
The motor and pump assembly are secured in a housing that can be submerged into the fuel cell, or in a case that is mounted on the chassis. Drop-in ready fuel cell modules are available for 6, 10, and 12-bolt mounting patterns and range in depth from 7.5 inches to 11 inches.
The motor and pump assembly are secured in a housing that can be submerged into the fuel cell or mounted on the chassis. Holley offers a number of configurations that include fuel-cell modules ready to bolt on to a traditional 6-, 10- or 12-bolt mounting pattern. The fuel pump depths in the tank are adjustable from 7.5 to 11 inches.
As noted earlier, brushless fuel pumps require a controller. Two are provided with the VR2 assembly, and the controllers are designed to work up to 18.5 volts. There is a simple way to wire the controller to run at full or half speed. If the signal wire is not grounded, it runs at 100 percent. If the signal wire is grounded, the pump runs at 50 percent speed.
However, the advantage of a controller is that the speed can be varied from 50 to 100 percent by a compatible ECU that is equipped with a PWM channel, such as the Holley Dominator ECU. Pulse-width modulation (PWM) allows engine tuners to control the fuel delivery according to the engine’s needs. The ECU already knows exactly how much fuel the engine needs at any given time, so it can use this information to speed up or slow down the pump to match those needs.
“If you’re circulating a high volume of fuel, you’re adding heat to that fuel,” explains Sosa. “Heat is a function of the fuel being compressed. You’re adding energy to the system and heating up the fuel unnecessarily. The big benefit of the VR series is the high flow when you need it and modest flow when you don’t.”
The ECU can be programmed for any number of scenarios to take advantage of PWM and the controllers used to operate the VR1 pumps. For endurance racing, the ECU can tell if a pump is starting to fail and automatically switch to the back up. For weekend racers and Drag Week-type vehicles, there can be a street and race mode.
“For those not running an ECU, the ground trigger on the controller can be wired to a Hobbs switch to move from half to full speed,” says Sosa. “A Hobbs switch is a pressure switch plumbed into the intake manifold that is normally opened until boost pressure is applied and then it closes.”
Holley devoted considerable engineering talent in developing the controller that can be used as a stand-alone or with a compatible ECU.
“You can get off-the-shelf controllers for brushless motors,” says Sosa. “But you can optimize the phase switching to your particular motor if you design your own controller. We matched the phasing to get the maximum torque and therefore the maximum flow. We also did a lot of life-cycle testing on the controller to make sure it would last.”
Holley encourages users to install a 100-micron pre-pump filter when setting up a VR pump, and a 10-micron or better filter past the pump. Both suggestions are available in Holley's billet filter line. Holley also offers VR regulators for both EFI and carbureted setups, and there’s a boost-reference regulator, if needed.