Fuel Pump Technology - How It Works

Feeding today’s horsepower demands with yesterday’s fuel pump technology is a losing proposition. Here’s a look at the latest the industry has to offer.

Stephen Kim Dec 21, 2011 0 Comment(s)
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Everyone knows that airflow equals power, but what about fuel? All the air in the world won’t make one single horsepower if it isn’t mixed with the proper amount of fuel in the combustion chamber. To illustrate the point, consider the age-old adage that “the really fast guys don’t care about dyno numbers.” If there’s an element of truth to this, there’s a very simple reason why. In the walk of classes like Outlaw 10.5 and Pro Mod, where severely boosted and squeezed motors often eclipse the 3,000hp mark, it’s hard to find a dyno that won’t go kaput when subjected to such extreme abuse. In this elite realm of combustion nirvana, where it’s difficult to directly measure engine output, calculating horsepower is all about keeping track of fuel consumption. Measure the volume and rate at which an engine burns fuel while going down the track, then compare it to well-established BSFC standards for engines of your type, and you’ll have a very good idea of how much horsepower it’s making.

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Obviously, feeding an engine the proper volume of fuel is a very big deal, and the incredible rate of horsepower proliferation in recent years has forced the aftermarket to keep pace. These days, dinky little in-tank pumps can flow as much as the big external race pumps of just a few years ago. Furthermore, massive fuel flow is no longer an eardrum-busting affair. Recent innovations have made it possible to fuel 2,000hp motors in whisper-quiet fashion. If it all sounds too good to be true, then there’s a good chance you need to get up to speed with the latest in fuel pump technology. To help you do just that, we got in touch of Jesse Powell of Aeromotive and Liz Miles of Holley, and had them explain it all to us. Chances are there’s an antiquated pump in your ride that’s begging for a replacement.

Carb Race Pumps

Jesse Powell: When it comes to serious drag racing, there are two common choices of pumps in Aeromotive’s lineup: the A2000 and our billet belt drive pump. The A2000 flows 350 gph, and is by far the most popular. This pump is a carbureted drag race–style pump, and it’s used by 80 percent of all Pro Stock racers, like Mike Edwards, Jeg Coughlin Jr., and Erica Enders. It is also the choice for most sportsman racers from Stock and Super Comp, all the way to some Pro Mods and Pro Nitrous racers. In high-horsepower EFI applications, our billet belt drive pump, PN 11105, is very popular. With the horsepower levels of extreme EFI engines, these types of mechanical pumps are becoming much more common. A mechanical pump is by far the most efficient way to provide that much fuel at EFI pressures. In fact, a good example is four-time Hot Rod Drag Week champion, Larry Larson. He runs a ’66 Chevy II with a twin-turbo EFI Moran big-block Chevy. When he races, he uses the belt drive pump. When he is running down the road for 1,300 miles during Drag Week, he fuels the motor with an A1000 fuel pump.

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Pump Design

Liz Miles: Fuel pumps can utilize different types of pumping mechanisms, and Holley pumps rely on both gerotor and rotor/vane designs. Our HP 125, HP 150, billet inline HP, and Dominator units are gerotor pumps, while the Red, Blue, and Black pumps use rotor/vane designs. The rotor/vane pumps consist of a round housing and round rotor mounted on an eccentric. The eccentric has vanes that push out to the inside walls of the housing, and the vanes push the fuel from the inlet to the outlet. These pumps are louder, largely because the vanes clatter and pulsate the fuel heavily while a gerotor doesn’t. They do a great job of pumping a lot of fuel at lower pressures.

The gerotor design has been proven to be extremely durable in OE applications. It uses a gear inside a housing that squeezes the fuel as it travels. This design is seen in oil pumps, which is another part that needs to be highly reliable. The design of these pumps enables turning as high as 4,000 rpm, resulting in higher pressure. The fuel lines don’t need to be as large in high-pressure fuel systems when compared to low-pressure systems, so using an HP or Dominator fuel pump can save weight. Furthermore, the gerotor’s tight tolerances and fine balance gives it super quiet operation compared to rotor/vane-style pumps.

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Medium HorsePower Pumps

Jesse Powell: In addition to serious race pumps that can support 2,000-plus horsepower, Aeromotive also offers high-quality pumps for your typical street machine. Our HO and SS pumps are designed for deadhead-style carbureted fuel systems. Although they’re not designed to flow as much as pumps like the A100, they’re still built to exacting tolerances for outstanding efficiency, performance, and durability. Both the HO and SS pumps boast all billet bodies and perfectly matched electric components for a truly high-quality pump. What I find crazy is that the HO pump still flows enough to support 600 hp. That is a good deal of power from a very simple fuel system. Additionally, the HO pump is internally regulated to 7 psi so you can actually run this pump without a regulator at all. The SS pump flows even more and can support 750 hp.

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Liz Miles: Most hot rodders are already familiar with Holley’s Red, Blue, and Black fuel pumps. They are rotor/vane-style pumps designed to flow high volumes of fuel at low pressures, perfect for low- to high-horsepower carbureted applications. The Holley Red pump flows 97 gph and supports 425 hp, while the Blue pump flows 110 gph and supports 550 hp. Stepping up to the Black pump yields 140 gph and 750 hp. Two more pumps in the medium-sized family are the HP 125 and HP 150. They feature billet bases, and are good for 750 and 900 hp, respectively.

Inline Pumps

Jesse Powell: When you look at the A1000, Eliminator, and Pro-Series pumps, you are talking about the most popular inline fuel pumps ever. It is very hard to compete with their flow capabilities and their durability. Although we have spent the last several years developing all sorts of new products, they have all been based around the A1000 and Eliminator design. They have just been packaged differently. Whether they are in a fuel cell or built into a system that drops right into your fifth-gen Camaro, they just flat out work. Our new designs have been done to provide users with worry-free performance and easy installation. Rather than hand a guy an A1000 for his Corvette and tell him “good luck,” we took the guesswork out of the equation. These new variants of our inline pumps drop right into your factory tank, use the factory lock-ring to seal, and still retain the tank siphon system and leveling unit. The pump is the last thing you will think about now. In the past, late-model Camaro and Corvette owners had to go with a fuel cell, or with a very expensive multi-pump setup, but with our Stealth systems, they can have serious flow with drop-in installation simplicity.

Liz Miles: For engines exceeding the power level of a HP 125 and HP 150 pumps fuel pump, Holley has developed a brand-new series of billet inline HP and Dominator pumps. These pumps will work in both carbureted and EFI applications, so using a return-style pressure regulator is required. There are two versions of the inline HP pump. The standard version will support 700 hp in naturally aspirated EFI motors and 900 hp in carbureted motors. The high-flow version of the HP pump is good for 900 hp in EFI applications, and 1,050 hp in carb motors. For truly extreme engine combos, Holley offers the inline Dominator pumps. The standard version supports 1,400 hp in EFI fuel systems, and 1,800 hp with a carb fuel system. The high-flow Dominator pump is good for 1,800 fuel-injected horsepower, and 2,100 carbureted horsepower. Additionally, Holley has a full line of matching regulators and filters for a wide variety of applications.

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Beltdriven Pumps

Jesse Powell: Two important factors to consider when deciding what fuel pump to go with is horsepower and fuel pressure. If you need enough fuel for 2,000-plus horsepower and it’s at EFI pressures, you are going to need a lot of pump. As pressure goes up, flow goes down. That’s why you can support more horsepower with a given pump at 7 psi carbureted than you can at 60 psi with EFI. This is why you see more mechanical pumps in high-horsepower EFI applications. Volume is really the key here. When you need a lot of volume, mechanical pumps are the only way to go. The physical size of an electric pump that could supply the same amount of volume as a mechanical pump would be ridiculous. Plus, the voltage requirements for an electric pump of this size would be very taxing on a car’s electrical system, especially when you consider that a mechanical belt drive pump, like the Aeromotive 1105, draws less than 1 hp to drive.

Heavy-Duty Mechanical Pumps

Liz Miles: Mechanical pumps still have their place. They are the simplest way to set up a fuel system. They don’t require an additional electrical circuit or any special fuel line routing. The HP pump doesn’t even require a regulator. Because of its relatively low operating pressure, the regulator for the Ultra HP fuel pump doesn’t need to be a return style, so even less plumbing is required. Our HP and Ultra HP mechanical pumps push up to 225 gph of fuel, more than even our HP 150 electric pump. In general, the Ultra HP mechanical pump is good for 1,000-plus horsepower depending on what fuel pressure and plumbing they run at. The HP mechanical pump can support 750-900 hp.

Small Pump, Big Flow

Jesse Powell: Some hot rodders accustomed to big external pumps will probably be skeptical upon hearing the advertised flow rates of the Aeromotive 340 in-tank pump. The 340 actually flows as much as the A1000 did about seven or eight years ago. This is all in a package that’s similar in size to a stock replacement in-tank EFI pump that fits right inside the factory hanger. Advancements in electrical motor technology have allowed us to steadily increase the output of all pumps. Motors are more efficient and powerful with less current draw than ever before. It is just the natural progression of things. Moving 340 lph of fuel at 43 psi, the 340 is very stout. That is enough for upward of 700 hp in a supercharged EFI motor. At carbureted pressure in a naturally aspirated combination, the 340 is rated at about 1,000 hp. That is something to write home about. We’ve been able to accomplish this through careful development of the proper electrical motor and mating it with a turbine-style pumping mechanism. These pumps are a take on the most common EFI fuel pumps ever created to date by the OEs. The OE pumps use a gerotor pump design. But with a turbine, we can spin it faster and more efficiently to produce a greater output. The key point in all this is that you can have OE durability and quiet operation, and still support the power you need in your factory tank. The 340 pump bridges the gap between the stock replacement in-tank pumps of old, and the A1000. It’s also extremely flexible since it can be used in both EFI and carbureted applications. All you have to do is match it up with the correct pressure regulator.

Proper Pump Mounting

Jesse Powell: If you talk to most hot rodders, they’ll probably tell you that big external pumps can’t be driven on the street for extended periods of time without vaporlocking because they run too hot. Here’s what’s actually going on. When you buy an Aeromotive pump like an A1000, you get a very detailed set of instructions. They state that the pump must be mounted below the tank or equal to the lowest level of the tank. They also state that the tank must be sumped, and to run an AN-10 feed line from the tank to the pump. If using a pre-pump filter, it is recommended that you use nothing smaller than 100-micron stainless steel. The reason for this is because fuel is no different than any other liquid. Think about your radiator and cooling system. It is under pressure because that pressure raises the boiling point of the coolant. The opposite is true if you put a liquid in a negative pressure environment or a vacuum. The boiling point is actually lowered. A fuel pump obviously pushes fuel to the engine at a desired pressure, but it also sucks fuel to itself. This suction creates a negative pressure environment of vacuum. So, when you use a pickup tube instead of a sump, the pump is no longer gravity fed. The area from the pickup tube to the inlet of a pump is in a vacuum and therefore it’s a place where the fuel can boil quickly. In most fuel system in most cars, fuel is cycled through the system. It goes from the tank to the engine and then is returned. With a pump like an A1000, the entire content of the tank is cycled every four to five minutes. Each time it cycles, the fuel picks up heat from the engine bay, the exhaust and the pavement getting hotter and hotter. Eventually the temperature of the fuel reaches a critical point in which it will actually boil in the pickup tube because of the negative pressure and artificially lowered boiling point. What then starts to happen is that the pump begins to cavitate because it is pulling the fuel to a vapor instead of pulling a liquid. The pump relies on the liquid fuel to keep it cool and lubricated. Eventually the pump or engine will quit because it cannot get fuel. If run dry long enough like this, the pump will vaporlock.

Avoiding these issues is very simple. If you are going to use an external fuel pump, make sure you follow the manufacturer’s recommendations carefully. In our case, it starts at the tank. You need to gravity feed your pump. A properly designed sump creates a new low point in the tank, ensuring fuel remains in that sump at all times, even until the last bit of the tank is emptied. Then, mount your fuel pump lower than the tank or level with that sump. That will keep the pump gravity fed or keep positive pressure on the pump inlet. Once again, remember that positive pressure raises the boiling point, so this set up will be much more forgiving. Also, make sure you use the right line size and a proper filter.

In-Tank Benefits

Jesse Powell: At Aeromotive, the trend we are pushing is to mount big pumps like the A1000 and Eliminator inside the fuel tank, as it eliminates all the problems associated with improper installation, cavitation, and vaporlock. In-tank mounting also results in a pump that’s much quieter. Submerged in the fuel is where a pump wants to be, and it’s the ideal environment for the pump. Since the pump is submerged, there is a constant column height of fuel pushing down on the inlet of the pump, creating a positive pressure environment. Plus, with the inlet of the pump in the fuel, there is no line size to worry about. This setup ensures quiet, cool operation of the pump. Proper tank baffling is also a huge issue. Ever since the OEs went predominately EFI in the mid ’80s, all tanks have been baffled or have some sort of basket inside to keep fuel at the point of pickup at all times. Now, most pumps are inside the tank, so they sit inside that basket or baffle. The problem with swapping a late-model EFI motor into an old muscle car is that old tanks have no baffles. As a result, whenever you stop hard, accelerate, or turn fuel moves away from the pickup, uncovering it and starving the pump of fuel. In EFI systems, there is no forgiveness so the engine suffers. Unlike a carb, an EFI fuel system does not store fuel in float bowls and does not operate at low pressure, so if the pump pickup is uncovered for a brief moment, it will sputter.

Staged Pumps

Liz Miles: Holley’s new flagship pump, the high-flow inline Dominator, boasts a long list of impressive features. Not only can it support up to 2,100 hp, but it also features billet aluminum construction for durability and good looks. The pump is very compact in size, measuring 7.5x5x2.5 inches, making it easy to mount in tight spaces. Additionally, the pump is fully submersible and can be mounted inside a fuel tank. A very unique feature of the Dominator is its dual pump design. With this arrangement, the motor can run off of one pump, and the second pump can be set up to activate on demand for nitrous or boost. This eliminates excessive recirculating and heating of the fuel. In applications that require massive fuel volume all the time, the second pump can be set up to run simultaneously as the primary pump. Despite its impressive flow, the Dominator weighs just 5.1 pounds.

Tank/Pump Combos

Jesse Powell: There are several great options for mounting an Aeromotive fuel pump internally. Companies like Rick’s Hot Rod Shop and Rock Valley offer stainless and aluminum tanks for almost any application with an A1000, Eliminator or even smaller pumps like our 340 Stealth built right in. They are a little on the higher end of the budget, but they provide you the ultimate combination of perfect performance, extra capacity, and great looks. Another option is going with one of Aeromotive’s Stealth Fuel cells, which have an A1000 or Eliminator pump built right in. The tanks have taken into consideration proper venting and quiet operation of the pump. All you do is drop it in, hook up your two lines and wires and you’re done. We see these being used a lot in Pro Touring vehicles, street/strip machines, and a lot of street trucks because it is so easy to drop between the framerails. If you already have a tank you want to use, we also offer universal A1000 and Eliminator Stealth systems. This is basically the same setup you see in the fuel cells, just in a universal application that allows users to turn any cell or custom tank into a Stealth tank. The key here though is going to be the fabrication. You can’t just drop this in. It does require a baffle like you see in our cells.

Perhaps the most exciting option is our new line of muscle car tanks that feature an in-tank fuel pump that provides the ability to support big horsepower. We have developed a first-gen F-body tank that is stamped and stock appearing that also features an internal baffle and a built-in 340 Stealth Pump. These tanks are perfect for the LS swap guy. They can support 700-plus horsepower in EFI motors, and 1,000 hp in carbureted motors. The baffling eliminates fuel slosh issues, and hot fuel handling and noise problems disappear because the pump is submerged. It’s like dropping a new Camaro tank into your muscle car. We hope to release these in early 2012 for ’67-69 Camaros with applications for ’64-72 A-bodies and Tri-Fives arriving shortly after. CHP

Sources

Aeromotive
Lenexa, KS 66214
913-647-7300
http://www.aeromotiveinc.com
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