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Fuel Delivery Systems

You Can't Make Big Horsepower Without A Big Pump, A Good Regulator, And A Well-Thought-Out

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'Pamela Anderson didn't get to where she is today by thinking small. When it comes to horsepower, the only way to make it big is to put fuel and air into the engine in vast quantities. While superchargers and nitrous will help on the oxygen side of things, you gotta think big when it comes to fuel delivery as well. A 51/416-inch fuel pickup in your '65 Mustang fuel tank will not feed even a 400hp small-block no matter how much pump you bolt on. We'll hit on several important points in this story, but the essential element is that a good fuel delivery system is exactly that-an integrated system where all the components work together to move fuel in the most efficient manner possible. Whether you're feeding a single four-barrel carburetor that fuels a 1,000hp Rat motor, or an EFI system with 60 psi of line pressure, there are certain fuel-system goals you must achieve to be successful. Get that done, and you can amaze your friends with how much quicker your car runs. Amazing Pamela may take a bit more effort. Call us if you're successful.

Fuel Pumps Let's start where everyone wants to use a bigger hammer. The aftermarket is crammed with pumps that can make a fire hose look like a lawn sprinkler. But do you need all that capacity? Let's find out.

This section will deal with electric fuel pumps since that's where all the high-performance pumps live. A typical 300hp street engine can survive nicely on a typical mechanical pump. But when you get up into the 500-plus horsepower range, fuel delivery becomes an essential consideration. Get into power adders with nitrous or blow-through superchargers, and a good electric fuel pump is an absolute necessity.

While those big electric fuel pumps may look glamorous, the first thing to consider is your application. If you have an 8-second drag-race car that never sees the street, then a high-volume upright pump like a BG 400 will work fine. For a streeter, an electric pump must be rated for continuous duty. For a high-volume, continuous-duty pump, the horizontal-style pumps are a better choice, since fuel runs through the pump. This is especially important in EFI applications, because more current is required to create those higher pressures, and more current also equals more heat. A big pump like the Aeromotive A1000 will require 10 amps to feed a 45-60-psi EFI application, but at 10 psi for a carburetor it may pull as little as 5 to 6 amps.

In all applications, the best approach is to match the pump to the engine's requirements. Often pump ratings in gallons per hour are at zero pressure. This rating is meaningless except for advertising hype since all fuel systems operate under pressure. A pump that's rated at 100 gallons per hour (gph) free-flow may only produce 60 gph at 5 psi. Look for pump ratings at the pressure the pump will operate. If you need 20 psi up to the regulator, for example, many pumps are far less efficient at that pressure than they are at 10 psi. Conversely, 5 psi is a reasonable fuel pressure for a mild street car as long as that pressure can be maintained under load. Let's look at what 60 gph will deliver. Most street engines operate at a brake-specific fuel consumption (BSFC) of 0.5 pounds of fuel per horsepower per hour (lb/hp/hr). Assuming fuel weighs 6.2 pounds per gallon, a 60-gph pump delivers (60 gph x 6.2) 372 pounds per hour of fuel. With a BSFC of 0.5, this means 372 lb/hr will support roughly (2 x 372) 744 hp. This is a stout number but doesn't take into account pressure losses within the system. Chances are a pump that can only deliver 5 psi will not be able to sustain that pressure as demand increases under load.

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