Dynamic vs. Static Fuel Systems
Traditional static fuel systems are more commonly found on carburetor applications and use a single line from the tank to the fuel pump. The fuel system's main priority is to prevent the carburetor bowl(s) from running low enough to uncover the main jets, and the second is to help maintain the fuel level in the bowl. The weight of the gasoline above the main jet affects fuel flow through the jet and the air/fuel ratio under load. Typically, this will work satisfactorily on vehicles with less than 500 horses. For very high-performance cars the float bowl must be kept as full as possible. In drag racing, a static system has difficulty keeping up with an engine developing lots of power. The problems begin at the starting line, where fuel inside the bowls is standing relatively still. Then as the car accelerates down the track, the fuel bowls begin to drain and the system begins to recover. As the floats rise, they again cut off the fuel flow. Fuel pressure in a static system is always maintained higher from the fuel pump to the regulator (typically 12-60 psi) than it is from the regulator to the carburetor (8-9 psi). Higher line pressure is necessary to start flow against g-force and to push fuel through the restrictive regulator valve. By design, the static-style regulator places the check valve between the fuel pump and carburetor, restricting fuel flow across the board. This requires the system to go through waves of operation.
A return-style regulator, or dynamic system, positions the inlet and outlet ports above the check valve with only the return volume serving to flow through the restriction. As a result, the pressure from the pump to the fuel regulator is the same as from the fuel regulator to the carburetor (typically 8-9 psi), which allows the pump to speed up, increasing volume significantly, and supplies constant full output to the float bowls.
The benefits of a dynamic, return-style fuel system are longer pump life, the elimination of unwanted pressure drops, a marked increase in pump-to-horsepower ratings, and quieter pump operation. This all means that a dynamic system allows for a more consistent air/fuel ratio across the rpm band and more predictable power all the way down. The only drawback to a dynamic system is the increased cost of fittings and lines.
Fit to Flow
Before installing any fittings, take a look inside. Not all fittings are created equal, and the wrong fitting can cause a restriction in your system. Most fittings supplied by the high-performance aftermarket are designed to maintain good flow, whereas those purchased from hardware stores or auto parts chains are more often sub par, often due to small id sizes.
When routing hard line or stainless braided AN lines, always avoid sharp-radius turns. Take time to map out your lines, and route them in a manner that provides the smoothest bends away from heat, suspension items, jacking points, and areas where the line could be impacted on the road or track. Depending on your application, you may opt to run a heat sink to reduce the fuel temperature. When selecting stainless braided AN lines, choose a size that will flow well enough to support your requirements. All AN sizes use a dash (-) preceding the number referring to the 1/16-inch-od thin-wall hard line to which the flexible line will compare. As an example, an AN-8 line would have the minimum id of an 8/16-inch (8/16 = 1/2). For most performance applications you'll want to run AN-8 or larger.