The advantages of using a mechanical fuel pump over an electric pump in extremely high-horsepower applications are substantial. All electric fuel pumps exhibit a flow curve that declines with pressure, simply because the electric motor that turns the pump has a fixed amount of torque and consequently slows down as the fuel pressure, or work load, increases. Conversely, Aeromotive says that the loss in flow as pressure rises is virtually nonexistent with its G-Rotor mechanical pump design. "This is due in part to the pump's efficiency, but primarily because it's driven directly by the crankshaft," Powell explains. "In other words, there is no way engine rpm is going to be affected by the fuel pump. If an electric pump is equivalent to a 3hp, 12V electric motor, the current draw it would impart on a 1,500hp motor would be so extreme that it could slow its rate of acceleration. In all-out competition, a beltdriven pump is simply a superior setup."
Deadhead VS. Return-Style Systems
Although most carbureted motors utilize deadhead-type fuel system, there is much potential for improvement in flow and pressure control by incorporating bypass regulators and return lines. This is particularly true with fuel pumps that don't have their own bypass capability. In the grand scheme of things, there isn't a single fuel system performance standard that doesn't improve when converting from a static (deadhead) to a dynamic (return-style) system. By running a bypass regulator, the pump can be set to run at lower pressure, thereby producing more flow, drawing less current, running quieter, and even lasting longer. Compared to a static setup, dynamic systems not only improve pump performance, but a bypass regulator also eliminates flow restrictions between the pump and the carburetor inlet. Plus, dynamic systems respond faster to fuel demand, and they do a better job keeping the float bowl full all the way down the track. In addition, dynamic systems never pressure-creep, which eliminates the engine flooding that static regulators can cause from time to time. The bottom line is that dynamic systems outperform static systems, and they simply produce the smoothest, most stable pressure curves. This has been proven in data logs from thousands of passes down dragstrips and laps around circle tracks.-Brett Clow
Electric VS. Mechanical Pumps
Electric fuel pumps make up the vast majority of pumps produced and sold by Aeromotive. They're uniquely flexible, able to serve in both low- and high-horsepower applications, and work on the street, at the track, and in EFI or carbureted applications. Done right, they just flat-out work.
Over the years, racers and enthusiasts have historically moved from diaphragm-style mechanical pumps to high-performance electric pumps when they need more flow. Nonetheless, as horsepower levels climb, there's a point where we go from electric pumps back to mechanical. However, the mechanical pumps in question are belt- or direct-driven units that bear little resemblance to traditional diaphragm-style pumps.
In the early part of 2001, modern horsepower levels in EFI applications passed the 1,500 hp mark and were rapidly moving toward the 2,000hp barrier. Aeromotive founder Steve Matusek realized that electric fuel pumps had a practical horsepower limit, as dual electic pumps wouldn't suffice in certain applications. Recognizing this void, he created a G-Rotor based, engine-driven mechanical pump along with a matching regulator that enables fueling 4,000hp EFI motors. It has taken a number of years for people to catch on, but in that time many of the top racers in today's heads-up ranks have won with Aeromotive mechanical pumps, including Chuck Samuel, Doug Mangrum, Donnie Walsh, Steve Petty and Tim Lynch, David Shore, and Gary Rohe. Of course, our in-house six-second drag car runs our billet hex drive pump and regulator.-Jesse Powell