Sure, it's twisted, but with gas prices so low these days, our idea of going green is burning as much of the stuff as possible while it's still cheap. You can't get much greener than the color of cash, and it will pump money into the economy to boot. Accomplishing such an altruistic endeavor requires a serious fuel system, and Aeromotive has the goods to get the job done. Since opening for business in 1994, the company's pumps, filters, and regulators have been the choice of countless street/strip enthusiasts and hardcore racers. In fact, the fastest nitrous-powered car on the planet, Mike Castellana's IHRA Pro Mod F-body, relies on an Aeromotive fuel system while ripping down the track in six seconds flat at 239 mph.
That said, it takes a lot more than a brute pump to survive the rigors of racing and street driving. "If you want to do it correctly, getting the fuel from the tank and into the engine is far more involved than you might think," explains Aeromotive's president, Steve Matusek. "When Aeromotive was formed, our original goal was to design and manufacture the best fuel pumps, filters, and regulators on the market. Our philosophy has evolved over to years to one where we develop entire fuel systems, not just individual components. Engineering components to work together within the tolerance of one another results in seamless performance and maximum durability and reliability."
To educate us on the subject, Jesse Powell and Brett Clow-two of Aeromotive's head tech gurus-gave us a condensed dissertation on fluid transfer dynamics and fuel system design. Our heads are still numb from trying to translate it all into something that resembles everyday English, but we think the results were well worth the effort. Some of what we learned was downright shocking. Little did we know that mechanical pumps trump their electric counterparts, and that just about every carbureted fuel system can benefit from running a return line. Are you ready to get pumped?
Calculating Flow Requirements
In the past, fuel pump manufacturers have rated their offerings based on gallons per hour of flow at an unspecified pressure, with no reference to test voltage. In the real world, this gave no indication of the horsepower that could be supported by their pumps. By choosing to assign a horsepower rating, along with publishing flow information at actual pressures and realistic voltages, Aeromotive has broken the mold and raised the bar for the industry. In the Aeromotive catalog, each pump carries several horsepower ratings on the basis of application type and use of power-adders.
The key variables that determine which fuel pump is suitable for a particular engine combination are horsepower, brake specific fuel consumption, maximum fuel system pressure, and the pump's flow volume at that pressure. Available voltage at the pump under engine load and the pump's flow volume at that voltage are important factors as well. To be safe, start by estimating horsepower on the high side and BSFC on the low side, which is usually less than one in most gasoline engines. Different engine combinations, power-adders, and even fuel octane ratings and tuning approaches will have a profound impact on BSFC, so consider this carefully when choosing a fuel pump.
Naturally aspirated engines are normally most efficient with a BSFC between 0.4 and 0.5 lb/hr. Nitrous combinations use a little extra fuel and often develop a BSFC from 0.5 to 0.6 lb/hr. Forced induction engines are usually the least efficient and have a BSFC ranging from 0.6 to 0.75 lb/hr. Determining the fuel volume necessary for a particular engine is the first step in selecting a fuel pump.-Brett Clow
Pressure And Volume
Designing a fuel system is a balancing act between pressure and volume. As system pressure goes up, the pump's volume goes down. "To illustrate this point, take a look at one of the most popular and efficient EFI pumps on the market, Aeromotive's A1000. Its flow volume is reduced 53 percent just by increasing line pressure from 9 to 90 psi," explains Powell. Although not quite as significant, he adds that the difference between 90 psi of line pressure and 60 psi with the same pump is a 28 percent drop in flow.
"A scenario like this isn't uncommon in forced induction EFI applications where fuel pressure is increased to compensate for undersized injectors. Clearly, the effect of raising fuel pressure has a significant impact on flow volume, and this is further compounded by low-quality fuel pumps. Obviously, eliminating unnecessary fuel pressure rise, removing FMUs, and installing properly sized injectors will increase flow and maximize the horsepower potential of any fuel system."